1. business and industrial
2. chemicals industry
3. plastics and polymers

WORK STATEMENT COVER SHEET
Date:
February 14, 2012
(Please Check to Insure the Following Information is in the Work Statement )
A. Title
B Executive Summary
C. Applicability to ASHRAE Research Strategic Plan
D. Application of the Results
E. State-of-the-Art (background)
F. Advancement to State-of-the-Art
G. Justification and Value to ASHRAE
H. Objective
I. Scope
J. Deliverables/Where Results will be Published
x
x
x
x
x
x
x
x
x
x
K. Level of Effort
Project Duration in Months
Man-Months: Principal Investigator
Man-Months: Total
Estimated $ Value
L. Other Information to Bidders (optional)
M. Proposal Evaluation Criteria & Weighting Factors
N. References
Responsible TC/TG:
Work Statement Authors:
David Ellerbrock
W/S#
36
5
23
180000
x
x
8.4
For
Against
Abstaining
Absent or not returning Ballot
Total Voting Members
Title:
Development of New Accelerated Corrosion
Test for All-Aluminum Microchannel and Tube and Fin
Heat Exchangers
1645
(To be assigned by MORTS - Same as RTAR #)
Results of this Project will affect the following Handbook Chapters,
Special Publications, etc.: Handbook chapters 21 and 35.
Work from this project will hopefully lead to the
development/acceptance of corrosion test standard
Date of Vote:
*
*
*
7
0
2
2
11
**
2/13/12
This W/S has been coordinated with TC/TG:
8.4
8.11
Has RTAR been submitted ?
Strategic Plan Theme/Goal(s)?
TC/TG Priority Rank:
(Which Year?)
Yes
Yes
1
2011
Implementation Plan Priority:
(Which Year?)
Proposal Evaluation Subcommittee:
Chairman: David Ellerbrock: [email protected]
Members:
Jay Matter: [email protected]
Hyunyoung Kim: [email protected]
Rusty Tharp: [email protected]
Mustafa Yanik: [email protected]
Mark Johnson: [email protected]
Project Monitoring Subcommittee:
(If different from Proposal Evaluation Subcommittee)
Name and Address of Recommended Bidders:
Brian Smith, ATS, 198 River Rd. Ridgeway,PA, 15853
[email protected] 814-773-3224
Alan Gray, Innoval Tech. Banbury, Oxfordshire, OX16 1TQ, UK.
[email protected], 44.129.570.2813
Modine Mnfg., 1500 DeKoven Ave., Racine, WI 53403
[email protected], 262-636-1683
Jay Matter, JCI, 5757 N. Green Bay Ave. Glendale, WI, 53209
[email protected], 414-218-9294
Potential Co-funders:
Sapa Group/Sapa Tech., Stefan Norgren, 612 81 Finspang, Sweden
[email protected], 46-122.832-16
Hydro Aluminum Precision Tube, Jan Halvor Nordlien, N-4265 Havik, Norway
[email protected], 47-952-95-899
(Three qualified bidders must be recommended, not including WS authors.)
Yes
Is an extended bidding period needed?
Has an electronic copy been furnished to the MORTS?
Will this project result in a special publication?
Has the Research Liaison reviewed work statement?
* Reasons for negative vote(s) and abstentions
One voter who abstained was unfamiliar
One voter who abstained was the committee chair
** Denotes WS author is affiliated with this recommended bidder
No
x
x
x
x
WORK STATEMENT: 1645
RESPONSIBLE TC/TG: TC8.4
Title
Development of New Accelerated Corrosion Test(s) for All-Aluminum Microchannel and Tube
and Fin Heat Exchangers
Executive Summary
The goal of this study is to identify or develop a new corrosion test(s) for all-aluminum microchannel
(MCHX) and round tube and plate fin (RTPF) heat exchangers that will encompass three realms which
have consequences for heat exchanger corrosion.
1. The atmosphere, including any pollutants, where the HEX is in use by an end-customer in a given
geographic location.
2. The heat exchanger alloy material system, defined as the chemical composition and inherent
thermo-mechanical history of the separate aluminum components (tube, fin, header, flux, etc.)
and the assembled heat exchanger itself.
3. The mode of operation of the heat exchanger.
The experimental work will focus on simplifying 1 and 3 by combining them, and make the results related
to an ISO standard for atmospheric corrosion severity.
Applicability to ASHRAE Research Strategic Plan
This research project will support the ASHRAE Strategic Plan in the following ways:
ASHRAE Goal #1 Maximize Operational Energy Performance, Goal #2 Progress toward NZE
Buildings: With a new understanding of which aluminum microchannel heat exchangers are
applicable to different atmospheric conditions, HVAC engineers will be able to flex other parameters
for optimized designs, thus saving energy and resources.
ASHRAE Goal #10 Understand Environmental Quality Needs and Education: The research will help
identify new equipment, procedures and techniques to access corrosion risk at different ambient
conditions.
ASHRAE Goal #9 Improved HVACR Components Reliability: This project supports cost savings
through the identification of insufficient or over-qualified microchannel heat exchangers for a given
environment. Subsequently, it prevents the loss of goods and services that result from corrosion
failures of HVAC systems, or additional costs of more expensive corrosion resistant systems.
ASHRAE Goal #10 Understand Environmental Quality Needs and Education: The information
gained from this research will be presented and published to the technical community, which will
strengthen ASHRAE’s role as technical leader.
Application of Results
The results of this study could be directly included in the Handbook of HVAC Systems and Equipment,
Chapter 21: Air-Cooling and Dehumidifying Coils and Chapter 35: Condensers. The standard corrosion
test would guide any ASHRAE member in deciding what type of heat exchanger alloy system would be
appropriate for a given operating mode and atmospheric corrosion system, thus saving time and
resources with lower costs. Similarly, the results of this study could be implemented by any ASHRAE
member that is trying to properly assess the corrosion resistance durability of an existing aluminum RTPF
or microchannel heat exchanger system with a standardized methodology that meets the criterion listed
below. Finally, a condenser could be compared to other defined test samples for determining the
corrosivity of an unknown corrosion system. Having a test method that better predicts performance would
save significant costs through many levels of the HVAC&R industry and enable more reliable products.
1
State-of-the-Art (Background)
Corrosion of Heat Exchangers
As stated in the Executive Summary, the goal of this study is to identify an existing standard test or
develop a new corrosion test for all-aluminum microchannel (MCHX) and round tube and plate fin (RTPF)
heat exchangers that will encompass three independent, but mutually inseparable, realms that have
consequences for heat exchanger corrosion. These three realms are:
1. the atmosphere, including any pollutants, where the HEX is in use by an end-customer in a given
geographic location,
2. the heat exchanger material system, defined as the chemical composition and inherent thermomechanical history of the separate aluminum components (tube, fin, header, flux, etc.) and the
1
assembled heat exchanger itself,
3. the mode of operation of the heat exchanger.
Each of these areas is well understood by their respective field of experts. However, the HVAC&R
industry has not taken fully into consideration the interaction of the atmospheric deposition of various
chemical compounds (realm 1) on the other two realms, (2) and (3). Rarely have each realm been taken
fully into consideration with previous cabinet-style tests, as discussed below, or specific field tests over a
scheduled time period.
There is a complex relationship of the environmental corrosion severity toward a metal depending upon
2
the heat exchanger duty cycle. For the purposes of this work, the corrosion system is defined as the
interaction between the atmosphere of interest and operation mode of the heat exchanger. Realms 1 and
3 are now combined.
The control of the governing factors within these realms for a designed experiment is difficult for a variety
of practical reasons. First, the alloy system is chosen by separate companies for their particular
manufacturing capability, available supplier components, product portfolio, and cost. The test chosen
must be applicable to all materials systems. For example, some systems use pure zinc applied to the
surface of the tube to create a sacrificial layer. Other systems use the fin alloy to be more or less anodic
to the tube. These different material systems may react relatively differently in different environments.
Second, the braze cycle for a MCHX is controlled by its manufacturer in such a manner that its
metallurgical properties may or may not be optimized for corrosion resistance compared to other product
features and efficient manufacturing operation. Thus, heat exchangers from different suppliers vary even
though their materials selections may be the same. For the purposes of this work, the HEX alloy systems
can be reasonably controlled by selecting sufficiently sized, known test populations. Of the three realms,
the corrosion system is the least understood. For example, weather can greatly influence the time of
wetness and the operating time, which in turn influence the deposition and accumulation of atmospheric
dust. Micro-environments exist due to nearby equipment and chemicals. The application environment is
often not controlled by a HEX manufacturer, nor an HVAC&R OEM, but by their end-use customers.
Even then, the environment is not really ‘controlled’ as much as a material system is selected as more
suitable for industrial, agricultural, rural, coastal, etc. regions. There is no ‘ownership for improvement’
over the true atmospheric influence.
1
A RTPF heat exchanger has relatively less thermal history compared to the MCHX style since it is not a brazed
product (except for the hairpin input and outlet connections) Both styles rely on aluminium alloys that were cast
and solidified under certain conditions, which affect their microstructure/property relationships for corrosion
durability.
2
ISO 9223 acknowledges that the metal of interest in a corrosion study may have design functions that influence
the surrounding local environment. Hence, there is a corrosion system formed by the combination of design and
atmosphere.
2
The reason for the inseparable nature between the other two realms – that of the atmospheric (1) and
alloy system (2) - is that metallurgical structure property relationships exist that influence the corrosion
resistance. The thermo-mechanical histories of the alloy components and the brazed HEX product can
make the overall corrosion resistance sensitive to a given atmosphere. The thermo-mechanical histories
span from the beginning of the aluminum melt operations of the raw billet at a cast house, to the extrusion
and roll forming sequences at the component supplier, and end with the mechanical strains and nearmelting temperatures imparted during assembly and brazing at the heat exchanger manufacturer. Each
of these operations in the value stream may change the corrosion behaviour of an alloy system
significantly if placed in even a moderately severe corrosion system.
History of SWAAT
For at least two decades, ASTM G85 annex 3, more commonly known as the Sea Water Acidic Acid Test
(SWAAT) has been used in the automotive industry for RTPF and microchannel heat exchangers. It
became established as a legacy test method with much history of data and institutional experience.
Since MCHX technology has migrated from the automotive industry to the HVAC&R industry, so has its
aluminum supplier base and customer expectations, including their use of SWAAT.
A good review of the development of accelerated corrosion cabinet testing has been undertaken by Lyon
et al. These authors point out that standardized atmospheric testing by American Society of Testing and
Materials (ASTM) in severe industrial – i.e. sulfur rich - environments were started in 1907 on a painted
railroad bridge in Maryland. Over the next one or two decades, it was realized by ASTM that sulfuric acid
was too severe to reliably simulate atmospheres. Nevertheless, a standard for the design and
construction of test apparatus, namely, a corrosion chamber, was first published in 1939 as ASTM B117.
B117 specifies the standard apparatus, procedure and conditions to create and maintain a constant (i.e.
continuously spraying), neutral pH salt (NaCl) test environment. A more aggressive and sophisticated
acidic chloride accelerated test was originally published as ASTM G43. It specified 42 g/L artificial sea
salt + 10 mL/L acetic acid, where the pH is between 2.8 and 3.0, and a spray period of 30 minutes,
followed by 90 minutes of dwell time. ASTM G85 was originally approved in 1985 and superseded G43.
Annex 3 of G85 specifies the current acetic acid, synthetic sea salt solution. There are two options for the
fog temperature: 35°C and 49°C, depending on the desire of the operator. These three standards do not
have a drying period, nor are they specific to HEX in terms of defining samples, nor the criterion for
failure.
Through experience, SWAAT results are not likely to be representative of all field conditions and failure
modes for aluminum HEX systems. For example, in coastal environments where the protective aluminum
oxide passive layer is stable due to the neutral pH environment, the aluminum can still be attacked
aggressively by localized corrosion via chloride salts. One significant, practical barrier of determining a
good correlation with automotive applications is that a condenser is not returned to the OEM unless it is
within a 3 to 10-year warranty period. This time frame is too short for a true corrosion failure of a robust
alloy system to occur and a proper analysis of the corrosion damage accumulation, especially since the
supplier may have already adopted a new design or alloy selection. The failure modes seen in field
failures are not always the same as typically witnessed in SWAAT. It must be noted that SWAAT only
simulates a single environmental condition, that being an acetic acidic atmosphere with high time of
wetness. Other environments clearly exist which are corrosive to aluminium heat exchangers. In these
environments, it is unknown whether SWAAT results correctly rank materials systems or correlate to field
durability. For this reason, other tests have been developed separately by automotive manufacturers. A
3
cursory list of automotive and military accelerated cabinet tests may be found online at one cabinet
manufacturer [2]. This list does not account for many other standards or proprietary tests developed for
specific customer applications. For example, a Calsonic Automotive test standard specifies the HEX be
dipped once into kaolin clay to act as a corrosion accelerant. This mud is then dried. Once placed into
the corrosion cabinet, hot water is circulated through the HEX, and then condensation and drying are
induced with the controlled RH and temperature inside the chamber (Jackson).
3
It is possible one of these tests may meet the purpose of this research if it conforms to the Scott criteria
discussed below.
3
However, SWAAT has been recognized as very useful for comparative analysis and a quality control tool.
Both of these aspects are very important for continuous improvement efforts of a given product. The
advantage of SWAAT is that it can quickly detect quality and processing defects. Here, there is not a
strict OK / not OK requirement for acceptability of a test result. It is expected that SWAAT will continue to
be used in this way.
Reasons for new accelerated test(s)
It is useful to briefly compare the ASTM G85 A3 SWAAT test conditions to show potential limitations in its
ability to accelerate field atmospheric environments and corrosion modes of interest. Table 1 is a partial
list of variables that compare SWAAT and atmospheric conditions.
Table 1. Comparison of Example Factors Between ASTM G85 A3 SWAAT and General
Atmospheres.
SWAAT
Atmosphere
Chloride
Y
Y and N
Acetic acid
Y
Y and N
SOX
N
Y and N
NOX
N
Y
Biological fouling
N
Y
Ammonia
N
Y and N
Time of wetness
constant
cyclic
In light of this comparison, it must be noted that SWAAT is an oversimplification of a natural environments
and only simulates one particular environment. Several questions arise in reviewing this comparison. Is
the environment simulated by SWAAT the most severe? Do we understand which environments and
operating modes are most severe? Are there environments and operating modes where the corrosion
mechanism changes? In these other environments and operating modes, does SWAAT still correctly
rank the material systems and can correlations be made? The answers to these questions are important
to determining the need for a new corrosion test for stationary HVAC.
Lyon et al have also pointed out a number of realistic, practical considerations that have driven
companies to increase the severity of a given corrosion test. Financial considerations have driven the
effort to reduce the times of corrosion testing time. These authors state that, “… in general they
(accelerated corrosion tests) have not been applied by virtue of their ability to simulate and enhance
natural weathering.” It is a difficult balance to develop a test that can be performed within a practical time
duration yet not be accelerated so much as to affect accuracy. This fact has led to occasional
consternation amongst those involved with corrosion testing. How is this?
Two questions are always asked by engineers, managers and customers relying on accelerated corrosion
testing and product deadlines. The first is, ″What is the lifetime correlation between the accelerated test
and the field for our product?“ In the case of the SWAAT test, the technical and theoretical answer must
be that a true correlation cannot be made unless the field environment has a near saturated humidity, a
pH of 3.0 with acetic acid, and 42 g/L sea salt 100% of the time. This is the environment simulated by
SWAAT. Of course, such a specific atmosphere is unlikely to exist naturally. The next question is, “When
can we have that correlation?” There is not a simple answer, as discussed below, and is the reason for
this research.
It is important to distinguish that an operational heat exchanger is not a static system, but a dynamic one
since it thermally radiates heat. Consequently, it creates its own microclimate and cycles the relative
humidity in intimate proximity. A relationship then exists between two variables: the mode of operation for
the HEX and the natural ambient weather. Both affect the corrosivity of the environment. Water
condensation at high relative humidity, as correlated with time of wetness (Tidblad et al) can accelerate
corrosion significantly. Another level of complexity is added when particulate matter (e.g. dust), with its
own chemical properties, settles on the coil and retains moisture. Further details are presented below.
4
Clearly then, simulation of different environments may require a more sophisticated approach which
accounts for the operation of the HEX in forming a microclimate both in proximity and on the surface of
the HEX.
Finally, tests run per ASTM G85 A3 can greatly differ in the time-to-failure of pressurized coils and the
degree of corrosion. SWAAT has been known to produce high variability in results across multiple tests
with the same cabinet and across cabinet-to-cabinet comparisons. It should be mentioned, however, that
Ashfar et al have shown with a statistical analysis of control samples that SWAAT result variation can be
caused by variation in material and quality variation rather than the test itself.
Natural weathering parameters
In order to understand the corrosion system and natural degradation of HVAC&R products, it is useful to
briefly categorize the natural weathering factors that can accelerate corrosion. Table 2 lists a number of
the factors that can influence corrosion. Greater discussion of Table 2 may be found in Tullman and
Roberge, Grossman, Guttman and Sereda, Carter, and Morcillo et al.
Table 2. Natural Weather Parameters that Affect Corrosion
A. Relative Humidity – General ranges:
Dry if < 30%
Normal if 50 < RH < 60%
Humid if > 80%
Saturated if = 100%
B. Rain – cleanses skyward facing surfaces, dissolves some soluble polluntants
C. Fog – absorbs pollutants and surface moisture layer
D. Condensation – either caused by natural cyclic night/day cooling and warming, or by dynamic
operation of an HEX application
E. Temperature – related to RH
F. Elevation – influences wind patterns, thermal layers, airborne coastal saline aerosols and
particulates
G. Wind – carries pollutants, dust and coastal saline aerosols
H. Gaseous / aerosol vapor pollutants- chloride, SOx, NOx, etc.
I. Dust - Composed of soot, soils, minerals, organic matter, metallic particles, etc.
These parameters may have additive effects that increase the amount of corrosion over time. How?
Accumulation of solid matter occurs gradually and subsequently promotes the creation of corrosion
mechanisms on aluminum in various ways. First, fine layers of dust or drying stains interfere with the
ideal dew point by lowering the threshold energy for dew droplet nucleation. These heterogeneous
nucleation points require less activation energy than a clean surface. Second, deposits may also have a
hydroscopic nature that retains moisture for longer periods of time. For example, depending on their
chemical composition, calcium and sodium, and other minerals commonly found in dust can absorb
moisture from the air.
Deposits or dust with various pollutant anions such as Fe or sulfur compounds and minerals can induce
passivity breakdown of the protective aluminum oxide layer. For example, Oesch and Faller have shown
the effect of common atmospheric gasses at different concentrations on the corrosion of aluminum in
controlled experiments.
A high frequency of condensation and drying tends to accelerate corrosion damage accumulation. Upon
evaporation, the concentrations of dissolved pollutants greatly increase. In this way, the pH can become
very acidic. Once dried, the residue may have a coarser texture that developed with repeated wet/dry
cycling patterns leading to further capture of dust.
Airflow through the fin louvers effects the moisture cycle, water drainage and droplet accumulation.
Particulate drop-out from the airstream below a certain velocity or impingement upon the leading coil
surfaces can leave patterns of soil deposition. Naturally, this is heaviest along the airside heat exchanger
5
face leading to corrosion patterns that may be related to the aluminium microstructure and its sensitivity
toward corrosion.
Deposits can also provide noble compound interfaces that induce microgalvanic effects (e.g. carbon and
various metals compounds) with the aluminum surface microstructure. Here, local micron-scale anode
and cathodes are established between the aluminum microstructure and the moist deposit such that
galvanic electrical and ionic currents begin to flow forming a closed circuit. If the deposits have a low
permitivity of air, then the aluminum beneath the deposit is susceptible to crevice corrosion, specifically
known as a differential aeration cell. This occurs by the formation of other reduction reactions beneath
the deposit that make the interfacial contact region acidic.
If dust deposits, wet dry cycling, or another factor creates a corrosion mechanism that is different than
that created in SWAAT and as a natural consequence the relative corrosion resistance of a materials
system is not correctly predicted by SWAAT, then a different test may be required. However, a cycling
test should not be prescribed if SWAAT correctly predicts the relative corrosion resistance in cyclic
operating condition of the heat exchanger, even though SWAAT itself is not a cyclic test. One key to the
success of this research project is determining what field conditions SWAAT is not correctly predicting
corrosion resistance. It is important to note there will likely be different correlations to different
environments and operating conditions.
Advancement to the State-of-the-Art
It is reasonable that any corrosion test for all-aluminum heat exchangers incorporates some of the factors
presented above. Namely, these are the mode of operation and atmospheric weathering factors
previously defined as the corrosion system. To that end, Scott et al proposed a reasonable, practical,
and scientific methodology that takes into account the metallurgical considerations necessary to develop
a new corrosion test. These researchers proposed that:
1.
2.
3.
4.
5.
6.
7.
The corrosion morphology must match the observed corrosion of field service samples.
The accelerated test environment must be a plausible replication of the atmosphere of interest.
The accelerated test sample is an accurate simulation of the system used in the field tests.
The measured criterion of corrosion was an appropriate measure of corrosion resistance in the field.
The test yields objective and quantifiable results.
The test duration had a reasonable timeframe.
The test would be an industry standard for adoption by others with similar interests.
A particular advancement of this work will be to link current ISO standards for assessment of atmospheric
corrosivity to this methodology for a new test. ISO 9223: Corrosion of metals and alloys-Corrosivity of
atmospheres-Classification, determination and estimation categorizes global atmospheric corrosion
severity as C1 Very low, C2 Low, C3 Medium, C4 High, C5 Very High and CX Extreme. These
categories may not be the same for different metals in the same location since they have different
structure/property relationships than aluminium. As discussed in this standard, the key variables that are
taken into account as the main drivers of metallic corrosion of static samples are atmospheric sulphur
deposition, chloride deposition, time of wetness and temperature. Interestingly, ASTM G85 annexes 4
3
3
and 5 call for the introduction of SO2 gas (1 cm /min-m ) while annex 6 calls for 0.35 w/o ammonium
sulphate salt solution.
The methodology of Scott listed above shall be the philosophy of the PI in developing the work if a new
test is deemed necessary. Different sources in the HVAC&R and automotive industries that have the
type of information of steps 1 through 4 are listed in Table 3. This table is meant to provide a snapshot of
the heat exchanger product value stream as a possible option to identify a path for information gathering
at the discretion of the PI for a better awareness of the Scott methodology.
6
Table 3. Chart for knowledge and information input for heat exchangers applications.
Aluminum
HEX
HVAC&R
End-use
ISO
Methodology Steps
component
manufacturer
OEM
customer
Standards
supplier
Corrosion
1 morphology of field
√
√
√
service units
2
Plausible replication
of environment
√
√
3
Accurate simulation
of system in the field
√
√
√
√
Measured criterion
4 of corrosion was the
appropriate measure
√
√
√
Justification and Value to ASHRAE
By having a data-driven understanding between the operating modes of an aluminium heat exchanger in
a defined corrosive environment to assess the corrosion durability of their product, ASHRAE members will
find value in a defined corrosion test procedure that can be related to global atmospheric corrosion
severity categories. Members that design large aluminium air condensers for any application, especially
residential A/C and commercial rooftop applications will benefit from this work. HVAC&R system
manufacturers will also be affected. Guidance from the new understandings will enable designers to
produce more corrosion resistant heat exchangers, thus preventing overdesign and more efficient heat
exchangers and systems.
Objective
The objective of this research is to develop a new corrosion test, or justify the use of an existing
standardized accelerated test, for both all-aluminum tube and fin and brazed microchannel heat
exchangers. The PI will first need to perform extensive literature searches to determine if existing
accelerated tests are deficient. The PI will work with the approach discussed above by Scott et al and
ISO standards to connect the work to what is known of atmospheric corrosive severity. The corrosion
system takes into account the operating mode and the resulting temperature-humidity complex. The PI
may work with an existing standard test or another corrosion-accelerant loading protocol if the literature
survey points in that direction, particularly with respect to the corrosion morphologies. Regardless of any
literature review findings, there must be a plausible and reasonable linkage between a defined
atmospheric corrosion system and the measured corrosion damage accumulation of aluminium heat
exchangers. Therefore, it is expected that the final outcome of this work will be the test methodology and
test results of at least one material system in at least one defined corrosion system. Ultimately, these
results will help create a standardized test that ASHRAE members can use to better predict HVAC&R
component and system performance for a given family of alloy systems based upon the atmospheric
conditions and mode of operation of an HVAC/HEX.
Scope / Technical Approach
To maximize the value of the work to the ASHRAE community, the PI is expected to work closely with the
PMS throughout the project as defined in the following Scope section.
Task I – Literature Reviews
There are three areas where literature reviews by the PI are necessary. The first is a summary of the
current cabinet-style accelerated corrosion tests, and any other form of accelerated test being used to
corrode aluminum HEX. It will be helpful to know what tests are being used for a particular HEX alloy
system to simulate a particular atmosphere (coastal, industrial, rural, agricultural, etc.) or operation mode
7
for a given application. For example, the Calsonic test discussed previously. The literature review should
access the applicability of such tests to the current work.
A second literature review by the PI should cover three the interrelated realms discussed above: 1) The
identification of important of atmospheric conditions and pollutants on the corrosion of aluminium; ISO
9223 and its related standards should be included here; 2) What is known to increase the overall
corrosion resistance behaviour of AA3000-series aluminum alloys used for HEX alloy systems; and 3)
how does the operation mode of the heat exchanger system cycle condensation and wetness layers for
given thermal loads, temperature, RH, air velocity, etc.
This literature review should offer guidance toward the design of an accurate test equipment setup for
environmental and atmospheric simulation, as well as the design of an experiment to identify the
boundaries (hi/lo salt concentration, frequency of wet/dry cycling, for example) of the simulation test. The
literature review should be discussed and reviewed with the PMS on a periodic interval leading to the final
review and approval of the work.
A third review should access the current usage of aluminum alloy HEX systems in different global
atmospheres or applications. This review should aim to understand corrosion modes that can occur in
stationary HVAC aluminium heat exchangers. Here, publicly available recommendations from an HEX or
HVAC&R producer to their customers should be compiled. A survey or discussion with the OEMs may be
helpful also.
Task II –Test Facility
Once the literature review is complete, the PI should outline the existing equipment and identify what
additional capital improvements are necessary to carry out the work statement at an existing test facility
or across multiple facilities. These equipment recommendations should be reviewed with the PMS, and
the PMS must approve any spending the PI proposes. Please note we assume that the PI has access to
an existing primary test facility with either climatic test chambers, potentiostats, atmospheric tunnel
testing, corrosion cabinets or other equipment deemed necessary after the literature search and approval
by the PMS. The final test facility proposal must demonstrate the ability to perform the necessary testing
either through past experimental achievements or affirmative input from an equipment provider.
Task III – Development of the Design of Experiment
The PI must present the approach taken toward creating the DoE to meet the criteria of Scott et al
(particularly item #1 for the corrosion morphology assessment), the actual proposed DoE, and then obtain
final approval from the PMS. The DoE with its identified variables and hi/lo ranges along the following
bullet point guidelines, guided by the literature review, is expected to be developed by the PI and
approved by the PMS:
The effective concentration levels of important and less important atmospheric pollutants which are
necessary to accelerate corrosion.
The atmospheric weather conditions which are important toward increasing corrosion severity.
Identification of the HVAC&R operation mode factors that increase corrosion severity for an aluminum
HEX and defined atmospheric conditions. Trends in these factors are also acceptable.
The source of any HEX used for sample populations, and their brazing thermo-mechanical process
control, if possible. The same requirement applies to any baseline samples. The tube wall thickness
should be kept the same for sample populations since this effects time-to-failure.
The time-to-first leak and/or its corrosion damage assessment of a heat exchanger sample will be
defined as the failure criteria, unless a compelling reason for another is approved by the PMS.
8
Task IV – Experimentation and Data Analysis
The PI will perform the DoE as outlined in Task III, and acquire all data necessary to develop and
4
evaluate the new corrosion test for at least one brazed material system and one RTPF material system.
A multi-factorial DoE will produce much data and experimental documentation of test conditions and
metallurgical results for corrosion damage metrics of the aluminium microstructures will be required. The
proposed tracking templates should be presented to the PMS prior to the start of testing. Statistical
reliability (Weibull distribution, for example) analysis should be used for the data assessment.
Task V – Experimental Reproducibility and Repeatability
Due to inherent variability in the metallurgical response of the aluminum alloys during brazing, a
population of microchannel HEX samples shall be collected from the same source at the same time and
used for this work. For tube and fin HEX, there shall also be a population taken from the same production
batch at a supplier.
The PI will demonstrate that test results are repeatable and should budget time and funding for a
validation test at the end of the experimental phase of the project.
Task VI– Report of Data and Results
The results of this research project must be reported as described below in the “Deliverables”. The PI is
expected to develop a work plan and format for reporting the data described in Tasks above.
Deliverables / Where Results Will Be Published
Intermediate Deliverable
Upon completion of the literature search the PI shall submit a written report outlining the findings,
reasoning, and recommendations for the work. The report shall also include a principal design of the test
facility and a draft test procedure and DoE. The TC 8.4 PMS will review, accept, revise or reject the
findings. This review will be a go/no-go gate, and PI shall not proceed without approval by the PMS.
Progress, Financial and Final Reports, Technical Paper(s), and Data shall constitute the only deliverables
(“Deliverables”) under this Agreement and shall be provided as follows:
a. Progress and Financial Reports
Progress and Financial Reports, in a form approved by the Society, shall be made to the Society through
its Manager of Research and Technical Services at quarterly intervals; specifically on or before each
January 1, April 1, June 1, and October 1 of the contract period.
Furthermore, the PI, subject to the Society’s approval, shall, during the period of performance and after
the Final Report has been submitted, report in person to the sponsoring Technical Committee/Task
Group (TC/TG) at the annual and winter meetings, and be available to answer such questions regarding
the research as may arise. The first such in-person report shall be immediately upon completion of Task I,
the literature review.
b. Final Report
A written report, design guide, test protocol, or manual, (collectively, “Final Report”), in a form approved
by the Society, shall be prepared by the Institution and submitted to the Society’s Manager of Research
and Technical Services by the end of the Agreement term, containing complete details of all research
carried out under this Agreement. In addition, the final report must include the design of equipment,
4
Microchannel heat exchangers brazed with zinc thermal spray coated AA3102 tubes are the most wellcharacterized coils within the automotive and HVAC&R industries since these were used for the early
development of NOCOLOK flux brazing technology, remain available from many manufacturers, and are
used in many applications. Accordingly, coils with these tubes should be considered as a possible
candidate for testing.
9
corrosion accelerant composition, operating mode of the HEX, and complete test procedure. Unless
otherwise specified, six copies of the final report shall be furnished for review by the Society’s Project
Monitoring Subcommittee (PMS).
Following approval by the PMS and the TC/TG, in their sole discretion, final copies of the Final Report will
be furnished by the Institution as follows:
An executive summary in a form suitable for wide distribution to the industry and to the public;
Two bound copies;
One unbound copy, printed on one side only, suitable for reproduction; and
Two copies on disks: one in PDF format and one in Microsoft Word.
c. Technical Paper
One or more papers shall be submitted first to the ASHRAE Manager of Research and Technical
Services (MORTS) and then to the “ASHRAE Manuscript Central” website-based manuscript review
system in a form containing such information as designated by the Society suitable for presentation at a
Society meeting. The Technical Paper(s) shall conform to the instructions posted in “Manuscript Central”
for a technical paper. The technical paper title shall contain the research project number (xxxx-RP) at the
end of the title in parentheses, e.g., (1111-RP).
Note: A research or technical paper describing the research project must be submitted after the TC has
approved the Final Report. Research or technical papers may also be prepared before the project’s
completion, if it is desired to disseminate interim results of the project. Contractor shall submit any interim
papers to MORTS and the PMS for review and approval before the papers are submitted to ASHRAE
Manuscript Central for review.
d. Data
All papers or articles prepared in connection with an ASHRAE research project, which are being
submitted for inclusion in any ASHRAE publication, shall be submitted through the Manager of Research
and Technical Services first and not to the publication's editor or Program Committee.
The Institution agrees to maintain true and complete books and records, including but not limited to
notebooks, reports, charts, graphs, analyses, computer programs, visual representations etc.,
(collectively, the “Data”), generated in connection with the Services. Society representatives shall have
access to all such Data for examination and review at reasonable times. The Data shall be held in strict
confidence by the Institution and shall not be released to third parties without prior authorization from the
Society, except as provided by GENERAL CONDITION VII, PUBLICATION. The original Data shall be
kept on file by the Institution for a period of two years after receipt of the final payment and upon request
the Institution will make a copy available to the Society upon the Society’s request.
e. Project Synopsis
A written synopsis totalling approximately 100 words in length and written for a broad technical audience,
which documents 1. Main findings of research project, 2. Why the findings are significant, and 3. How the
findings benefit ASHRAE membership and/or society in general shall be submitted to the Manager of
Research and Technical Services by the end of the Agreement term for publication in ASHRAE Insights.
The Society may request the Institution submit a technical article suitable for publication in the Society’s
ASHRAE JOURNAL. This is considered a voluntary submission and not a Deliverable. Technical articles
shall be prepared using dual units; e.g., rational inch-pound with equivalent SI units shown
parenthetically. SI usage shall be in accordance with IEEE/ASTM Standard SI-10.
Level of Effort
It is expected that the Tasks above will take approximately three (3) years to complete. The expected
total cost for this work is $180,000.
10
Principal Investigator (~20 man weeks):
Graduate Student (~72 man weeks):
Facility cost with upgrades:
Acquisition of test samples coils:
Miscellaneous items (travel, etc.):
$80,000
$40,000
$30,000
$20,000
$10,000
Other Information to Bidders (Optional):
It is expected that the investigators bidding for this work will have relevant experience, as evidenced by
their publications in peer-reviewed journals, professional conference proceedings, or past work involving
AA3000-series aluminium alloys, corrosion testing, and thermal testing of refrigerant to air condensers or
similar heat exchanger.
Proposals
Proposals submitted to ASHRAE for this project should include the following minimum information:
1. Statements describing test facilities, equipment and capabilities to be utilized. The exact
specifications and dimensions of the test equipment, including instrumentation and description of
data collection across a heat exchanger, and metallographic analysis for corrosion damage metrics
on samples must be included in the proposal.
2. How objectives would be met to fulfil the design of experiment and what procedures would be used
to achieve them. Descriptions of how necessary measurements for the coolant inlet and outlet
temperature, pressure, RH, airflow rate, determination of heat transfer, pressure drop, time-ofwetness, and gaseous pollutants in the airstream must be addressed in the proposal. Descriptions
of how these measurements will be made must be clear in the proposal including statistical
variation, thermal performance/operation mode control, and atmospheric control.
3. Statements indicating experience and publications in conducting research associated with
performing heat transfer, corrosion testing, atmospheric monitoring and materials science.
4. Resume of the Principal Investigator and others involved in the study.
5. Planned schedule and length of time for the project to be completed.
6. Budget information and information of any other co-sponsors.
Proposal Evaluation Criteria
The commonly used evaluation criteria include:
The commonly used evaluation criteria (and sample weighting factors) are listed below. The WS may
include some or all of these criteria, using whatever weighting factors the TC feels are appropriate. For
example, a project involving simulation models may not depend upon “facilities,” while experience of the
PI in simulation modelling may be crucial. For performance testing of appliances, however, the quality of
the Contractor’s facilities may be very important.
1.
2.
3.
Contractor's understanding of Work Statement as revealed in proposal
a)
Logistical problems associated
b)
Technical problems associated
Quality of methodology proposed for conducting research
a)
Organization of project
b)
Management plan
Contractor's capability in terms of facilities
a)
Managerial support
15%
25%
15%
11
4.
5.
6.
7.
8.
b)
Data collection
c)
Technical expertise
Qualifications of personnel for this project
20%
a)
Project team 'well rounded' in terms of qualifications and experience in related work
b)
Project manager person directly responsible; experience and corporate position
c)
Team members' qualifications and experience
d)
Time commitment of Principal Investigator
Student involvement
5%
a)
Extent of student participation on contractor's team
b)
Likelihood that involvement in project will encourage entry into HVAC&R industry
Probability of contractor's research plan meeting the objectives of the Work Statement
15%
a)
Detailed and logical work plan with major tasks and key milestones
b)
All technical and logistic factors considered
c)
Reasonableness of project schedule
Performance of contractor on prior ASHRAE or other projects.
5%
(No penalty for new contractors.)
Other _________________________
References
1. S. B. Lyon, G. E. Thomson, and J. B. Johnson, “Materials Evaluation Using Wet-Dry Mixed SaltSpray Tests,” Standard Technical Publication 1133, American Society for Testing and Materials,
1916 Race Street, Philadelphia, PA, pp. 20-31.
2. http://www.ascott-analytical.com/standard-corrosion-tests.html
3. Jackson, ″Sacrificial Layer Protection for Condenser Corrosion Resistance,“ C496/093/95, Society
of Automotive Engineers, IMechE 1996, pp. 421-427.
4. Note: This paper references Calsonic Test Standard CTCE.02.1-013 Dew Testing, Calsonic Tech.
Centre-Europe, Dyfed, S. Wales, which has greater detail of the kaolin clay corrosion test. Efforts
to find this standard have not been successful by this work statement author. Any assistance in
obtaining the this test protocol would be appreciated.
5. J.Tidblad, A. A. Mikhailov and V. Kucera, “A relative humidity and temperature model for time of
wetness prediction,” Swedish Corrosion Institute, Stockholm, Sweden. Note: The author is
obtaining the complete publication source.
6. M. Tullman and P.R. Roberge, Chap. 18 Atmospheric Corrosion, Uhlig’s Corrosion Handbook,
Second Edition, Edited by R. Winston Revie, John Wiley & Sons, Inc. 2000, p305-321.
7. Grossman, P.R.,“ Investigation of Atmospheric Exposure Factors that Determine Time-of-Wetness
of Outdoor Structures,“ Atmospheric Factors Affecting the Corrosion of Engineering Metals, ASTM
Special Technical Publication 646, S.K. Coburn, Ed., American Society for Testing and Materials,
p5-16.
8. Guttman, Herbert and Serada, P.J., “Measurement of Atmospheric Factors Affecting the Corrosion
of Metals,“ Metal Corrosion in the Atmosphere, ASTM Special Technical Publication 435, American
Society for Testing and Materials, pp. 326-359.
9. V.E. Carter, “Atmospheric Corrosion of Aluminum and Its Alloys: Results of Six-Year Exposure
Tests,“ Metal Corrosion in the Atmosphere, ASTM Special Technical Publication 435, American
Society for Testing and Materials, pp. 257-270.
10. M. Morcillo, B. Chico, L. Mariaca, E. Otero, “Salinity in marine atmospheric corrosion: its
dependence on the wind resime existing in the site“, Corrosion sceience 42 (2000) 91-104.
12
11. S. Oesch and M. Faller, “Environmental Effects on Materials: The Effect of the Air Pollutants SO2,
NO2, NO and O3 on the Corrosion of Copper, Zinc and Aluminum. A Short Literature Survey and
Results of Laboratory Exposures”, Corrosion Science 39(9), (1997) 1505-1530.
12. A.C. Scott, R.A. Woods, and J.F. Harris, “Accelerated Corrosion Test Methods for Evaluating
External Corrosion Resistance of Vacuum Brazed Aluminum Heat Exchangers,” Society of
Automotive Engineers Technical Paper Series 91050, International Congress and Exposition,
Detroit, Michigan, February 25-March 1, 1991.
13. ISO 9223 Corrosion of metals and alloys - Corrosivity of atmospheres - Classification,
determination and estimation.
14. F.N. Afshar, E. Szala, A. Wittebrood, R. Mulder, J.M.C. Mol, H. Terryn, J.H.W. de Wit, “Influence of
material related parameters in Sea Water Acidified Accelerated test, reliability analysis and
electrochemical evaluation of the test for aluminium brazing sheet,” Corrosion Science 53 (2011)
3923-3933.
Authors
The primary author of this work statement was:
David Ellerbrock
Global Manager Materials Science and Technology
United Heat Exchanger Technology Center
Kemptenerstrasse 99
88131 Lindau, Germany,
[email protected]
[email protected]
49 151 1424 8239
13
Unique Tracking Number Assigned by MORTS _____1645-RTAR_______________________
RESEARCH TOPIC ACCEPTANCE REQUEST (RTAR) FORM
TC: 8.4 Air-to-Refrigerant Heat Exchangers
Title:
Development of New Accelerated Corrosion Tests for All-Aluminum Microchannel and Tube
and Fin Heat Exchangers.
Applicability to ASHRAE Research Strategic Plan:
This research project will support the ASHRAE Strategic Plan in the following ways:
ASHRAE Goal # 1Maximize Operational Energy Performance, Goal #2 Progress toward NZE Buildings: With
a new understanding of which aluminum microchannel heat exchangers are applicable to different atmospheric
conditions, HVAC engineers will be able to identify other parameters with optimized designs, thus saving
energy and resources.
ASHRAE Goal #10 Understand Environmental Quality Needs and Education: The research will help identify
new equipment, procedures and techniques to access corrosion risk at different ambient conditions.
ASHRAE Goal #9 Improved HVACR Components Reliability: This project supports cost savings through the
identification of insufficient or over-qualified microchannel heat exchangers for a given environment.
Subsequently, it prevents the loss of goods and services that result from corrosion failures of HVAC systems, or
additional costs of more expensive corrosion resistant systems.
ASHRAE Goal #10 Understand Environmental Quality Needs and Education: The information gained from
this research will be presented and published to the technical community, which will strengthen ASHRAE‟s
role as technical leader.
Research Classification:
Basic/Applied Research
TC/TG Priority:
#1
TC Vote:
(8 –0-4-0-12)
Reasons for Negative Votes and Abstentions:
(Abstentions – no response)
Estimated Cost: $180,000
Estimated Duration: 36 months
Other Interested TC/TGs:
TC 8.11 voted 8-0-4 in favor of co-sponsorship
Possible Co-funding Organizations:
Sapa Technology, Alcan, Alcoa, Innoval, Hydro Aluminum, Güntner
Application of Results:
Handbook of HVAC Systems and Equipment, Chapter 21: Air-Cooling and Dehumidifying Coils
Handbook of HVAC Systems and Equipment, Chapter 35: Condensers
State-of-the-Art (Background):
The HVAC industry has adopted American Society of Testing Standard G85 Annex 3 for corrosion testing of brazed
aluminum microchannel heat exchangers. This trend was because microchannel technology had been developed in
the automotive industry in the early and middle 1980s and spread to become state-of-the-art for that industry. The
standard has roots going back several decades to the beginning of the 20th century, and has been used extensively by
all major automotive thermal component suppliers simply due to its severity. However, it is not clear if G85 A3 is
the right test to reproduce corrosion damage and failures as seen in end-user environments.
ASTM G85 A3 is commonly referred to as SWAAT – the sea water acetic acid test. It involves wetting of samples
with a low pH, high chloride mist for 30 minutes, and then letting the cores „soak‟ for 90 minutes before this cycle is
repeated. There is no complete drying period, as occurs in natural environments with morning dew, then droplet
TC8 4 RTAR New Corrosion Test_10May2011.docx
evaporation, etc. which can accelerate localized corrosion. Lyon et al [1], in their concise review of accelerated
testing and atmospheric factors that cause severe corrosion, discuss how SWAAT bears little resemblance to real
environments. In fact according to them, the test was developed for practical cost- and time-saving reasons rather
than to develop a correlation to field exposures. After all, greater severity means less cost per test both in terms of
labor and time. They state, “… laboratory accelerated test methods…have not been applied by virtue of their ability
to simulate and enhance natural weathering.”
At least one research group (Scott et al, [2]) found SWAAT to reproduce corroded radiator microstructures of
corroded regions of aluminum AA3003/AA3005 brazing sheet. However, correspondence between the author and
several aluminum tube extrusion and brazing experts indicate [3] that SWAAT does not accurately replicate the
failure modes that appear in the field under varying customer duty cycles and environments. This statement is
especially true for aluminum multi-port extruded tubes (MPE) with their many alloy and processing requirements to
meet environmental requirements for the HVAC industry. More specifically, SWAAT test failure modes depend
upon the aluminum alloy technologies and component (tube, fin, and header) combinations that are complimentarily
selected to enhance the corrosion resistance of the entire heat exchanger. For example, it is known that non-brazed
microchannel tubes can fail SWAAT in less than ten days, but when brazed with sacrificial fins, the tubes will not
suffer corrosion perforation for much longer time [4]. Even the Scott group recognized that their findings were not
applicable to new (at that time) K319 aluminum alloy sheet since field data was not available.
Advancement to the State-of-the-Art:
The Scott group outlined a reasonable set of valid criteria necessary for development of a qualifying test. These are
stated here with brief comments:
1. The mode of attack - corrosion morphology - matched the corrosion observed in samples returned from
field service. This information is obtained by metallographic inspection of corroded samples. A ranking of
the degree of intergranular or pit corrosion can then be generated, for example.
2. The accelerated test environment was a plausible analog of the field experiment. Known atmospheric
pollutants and the weathering parameters that induce corrosion (dew point, time of wetness, chloride or
sulfur concentration, as examples) can be evaluated to propose new test conditions.
3. Similarly, the test specimen was an appropriate model of the material as used in the field. The test
specimen should be representative of product in the industry. It may be feasible to test „worst and best‟ case
material conditions to establish boundaries of corrosion behavior.
4. The test performance criterion was an appropriate measure of corrosion resistance in the field. A metric of
interest will have to be chosen to define corrosion resistance. For example, criterion may include
perforation time to 50% of aluminum microchannel tube wall thickness, loss of 60% of thermal
performance, or simply time-to-leakage failure (most common) of the heat exchanger.
5. The test gave objective, quantifiable results. The metric chosen as part of #4 will have to be reproducible
and repeatable across different laboratories.
6. Test duration was reasonably short.
7. The test was an industry standard, and could be readily put into use by other aluminum producers, radiator
manufacturers, etc. The cost of testing may drive these last two criteria.
Industry leaders using aluminum brazed heat exchangers have separately developed internal corrosion tests.
Recently, published work to mimic field conditions includes the X-SACT test from Norgren and Elk [3]. This test
uses a less acidic solution (pH4 rather than pH3) and a lower concentration of sodium chloride (1%) than SWAAT,
but introduces four drying periods in one hour. The wet-dry cycle is particularly important for reproducing field
conditions since water droplets exhibit a progressively lower pH and higher chloride concentration as they
evaporate. This phenomenon drives the corrosion rate. It also meets the second of Scott‟s criteria. Ammonium
sulfate is also added since it is found in coastal and agricultural regions; Ammonium sulfate increases the corrosion
rate. Norgren and Elk reported that light tube corrosion in X-SACT resembled known attack found in the literature,
but to resemble is not to be identical. The X-SACT test debonds the fin from Zn-coated tubes in a similar manner as
SWAAT. It is a drawback that the test takes longer to run than SWAAT despite the wet/dry cycles which should
have greatly accelerated corrosion. Nevertheless, X-SACT is advancement, but like the Scott group, Norgren and
Elk clearly state their research is limited by the lack of field samples exposed to end-customer environments.
Justification and Value to ASHRAE:
TC8 4 RTAR New Corrosion Test_10May2011.docx
Progress has been made by separate groups and companies on each of Scott‟s criteria, but for proprietary and
competitive market reasons, have not been linked with others‟ results. The intent of this proposal is to have a much
greater, and new, knowledge of how atmospheric corrosion mechanisms result in loss of performance and
catastrophic system failure for global HVAC applications. A scientifically valid and fundamental understanding of
a new test method that replicates field observations will help ASHRAE members reduce costs significantly.
ASHRAE is the organization that can pull the necessary information from various resources, particularly operating
units retrieved from the field, while still protecting members‟ interests.
Objectives:
This project will seek to develop for the HVAC industry at least one new corrosion test that replicates field
corrosion failure modes and allows comparison or ranking between all-aluminum brazed MCHX and fin & tubetype heat exchangers fabricated from key types of manufacturing combinations. For example, wet NOCOLOK flux
brazing and flux coatings applied to the microchannel tube. The steps below broadly outline part of the work, and
address the applicable criteria of Scott.
1.
A detailed literature search shall be performed to review past work on the subject, including biological
corrosion.
2.
Field failures of heat exchangers will be gathered from the field for metallographic analysis of the
corrosion morphology and chemical analysis of deposited atmospheric residues. Documentation of
environmental composition and corrosion modes can then be categorized with global location and alloy
systems. These steps help address criteria #2 and #3.
3.
A test solution and test matrix should both be developed based upon input from corrosion, materials, and
field exposure experts within the industry (criteria #2, 3, and 4)
o New test solutions of varying pH, salt concentration, and known atmospheric pollutants will be
identified based upon available research of atmospheric corrosion, including rural, coastal and
industrial areas.
o An experimental test matrix will be developed that varies the pH, salt concentration, industrial
pollutants, wet/dry cycles, and other factors into high and low regimes to generate meaningful
test responses.
o Considerations of known accelerated corrosion test results of commercially available
components should be combined with the proposed solution and test matrix to guide new tests.
4.
Tests will then be performed to generate corrosion failures for evaluation. These microstructures and
times-to-failure will then be compared to known field samples collected in #1 above (criteria 4, 5, 6, and
7).
5.
An objective of more practical importance will be corrosion testing of dissimilar metal connection joints.
For example, brazed aluminum and copper joints with zinc-rich fluxes
Key References:
[1] S. B. Lyon, G. E. Thomson, and J. B. Johnson, “Materials Evaluation Using Wet-Dry Mixed Salt-Spray Tests”,
Standard Technical Publication 1133, American Society for Testing and Materials, 1916 Race Street, Philadelphia,
PA 19103, pp. 20-31.
[2] A.C. Scott, R.A. Woods, and J.F. Harris, “Accelerated Corrosion Test Methods for Evaluating External
Corrosion Resistance of Vacuum Brazed Aluminum Heat Exchangers”, Society of Automotive Engineers Technical
Paper Series 91050, International Congress and Exposition, Detroit, Michigan, February 25-March 1, 1991.
[3] D. Ellerbrock (UHTC) and J. H. Nordlien (Hydro Precision Tubing Technology Centre), S. Norgren (Sapa
Technology) H.-W. Swidersky (Solvay Fluor), private communications.
TC8 4 RTAR New Corrosion Test_10May2011.docx
[4] D. Ellerbrock (UHTC) and J. H. Nordlien (Hydro Precision Tubing Technology Centre), private communication.
[5] S. Norgren and L. Elk, “Corrosion performance & testing of CAB aluminum heat-exchanger samples for
HVAC&R”, 1st International Congress Aluminum Brazing Technologies for HVAC&R, Aluminum-Verlag,
Dusseldorf, Germany, 16-17 June 2009.
TC8 4 RTAR New Corrosion Test_10May2011.docx