ASTM D7356/D7356M-19

Standard Test Method for Accelerated Acid Etch Weathering of Automotive Clearcoats Using a Xenon-Arc Exposure Device

SIGNIFICANCE AND USE
5.1 Acid etch damage is an important warranty claim item for automotive companies. As a result, acid etch resistance is an important parameter for automotive exterior coatings. The method described in this test method has been shown to simulate acid etch damage of automotive clearcoats that occurs when such coatings are exposed from May through mid-August in Jacksonville, FL.3,5 The accelerated test described in this standard allows year-round testing as opposed to the limited outdoor exposure time available for the Jacksonville, FL exposures.
SCOPE
1.1 This test method covers an accelerated exposure test intended to simulate defects in automotive clearcoats caused by acid rain2 that occur at the Jacksonville, Florida exposure site. Exterior exposures at an acid rain test location in Jacksonville, Florida produce etch defects that range from small pits to 12.7 mm [0.5 in.] in diameter or larger acid-etched spots. The latter type of defect is not produced in other acid-etch tests that only produce pits that are smaller than 6.35 mm [0.25 in.] in diameter.3
Note 1: Digital images of the acid etch defects produced in outdoor acid-rain exposures and in the accelerated test described in this test method are found in Appendix X1.  
1.2 The accelerated test described in this test method uses a xenon-arc light source with daylight filter conforming to the requirements of Practice G155. Specimens are sprayed with a simulated acid rain solution and requires the use of a horizontal, flat specimen array in order to allow the acid rain solution to remain on the test specimens for an extended period of time.  
1.3 There is no known ISO equivalent to this test method.  
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 14-Nov-2019
• ICS: 43.040.60 - Bodies and body components
• Technical Committee: D01 - Paint and Related Coatings, Materials, and Applications
• Drafting Committee: D01.27 - Accelerated Testing

Relations

• Replaces: ASTM D7356/D7356M-13 - Standard Test Method for Accelerated Acid Etch Weathering of Automotive Clearcoats Using a Xenon-Arc Exposure Device
• Effective Date: 15-Nov-2019
• Refers: ASTM G147-17 - Standard Practice for Conditioning and Handling of Nonmetallic Materials for Natural and Artificial Weathering Tests
• Effective Date: 01-Jun-2017
• Refers: ASTM G113-14 - Standard Terminology Relating to Natural and Artificial Weathering Tests of Nonmetallic Materials
• Effective Date: 01-Mar-2014
• Refers: ASTM D1293-12 - Standard Test Methods for pH of Water
• Effective Date: 01-Jan-2012
• Refers: ASTM G151-10 - Standard Practice for Exposing Nonmetallic Materials in Accelerated Test Devices that Use Laboratory Light Sources
• Effective Date: 01-Apr-2010
• Refers: ASTM D4517-04(2009) - Standard Test Method for Low-Level Total Silica in High-Purity Water by Flameless Atomic Absorption Spectroscopy
• Effective Date: 01-Oct-2009
• Refers: ASTM G151-09 - Standard Practice for Exposing Nonmetallic Materials in Accelerated Test Devices that Use Laboratory Light Sources
• Effective Date: 01-Jul-2009
• Refers: ASTM G113-09 - Standard Terminology Relating to Natural and Artificial Weathering Tests of Nonmetallic Materials
• Effective Date: 15-Jun-2009
• Refers: ASTM G147-09 - Standard Practice for Conditioning and Handling of Nonmetallic Materials for Natural and Artificial Weathering Tests
• Effective Date: 01-Feb-2009
• Refers: ASTM G113-08 - Standard Terminology Relating to Natural and Artificial Weathering Tests of Nonmetallic Materials
• Effective Date: 01-Aug-2008
• Refers: ASTM G113-06e1 - Standard Terminology Relating to Natural and Artificial Weathering Tests of Nonmetallic Materials
• Effective Date: 01-Dec-2006
• Refers: ASTM G113-06 - Standard Terminology Relating to Natural and Artificial Weathering Tests of Nonmetallic Materials
• Effective Date: 01-Dec-2006
• Refers: ASTM G151-06 - Standard Practice for Exposing Nonmetallic Materials in Accelerated Test Devices that Use Laboratory Light Sources
• Effective Date: 15-Nov-2006
• Refers: ASTM G155-05a - Standard Practice for Operating Xenon Arc Light Apparatus for Exposure of Non-Metallic Materials
• Effective Date: 01-Oct-2005
• Refers: ASTM G113-05 - Standard Terminology Relating to Natural and Artificial Weathering Tests of Nonmetallic Materials
• Effective Date: 15-Aug-2005

Overview

ASTM D7356/D7356M-19 is the Standard Test Method for Accelerated Acid Etch Weathering of Automotive Clearcoats Using a Xenon-Arc Exposure Device. Developed by ASTM Committee D01, this standard provides procedures for simulating and evaluating the durability of automotive clearcoats against acid etch damage, a common issue associated with acid rain exposure. Using an accelerated laboratory technique, this standard enables manufacturers and laboratories to reliably assess acid etch resistance in automotive coatings throughout the year, overcoming the limitations of outdoor exposure tests tied to seasonal weather conditions.

Key Topics

• Accelerated Acid Etch Testing: The methodology describes an accelerated exposure test for automotive clearcoats, focusing on simulating defects-such as pits and acid-etched spots-caused by acid rain, particularly as observed in Jacksonville, Florida, a known acid rain test site.
• Xenon-Arc Exposure: The test utilizes a xenon-arc exposure device equipped with daylight filters. Test panels are sprayed with a simulated acid rain solution and subjected to controlled cycles of light and dark exposure, temperature, humidity, and periodic pure water sprays.
• Test Setup and Evaluation:
  • Panels are arranged horizontally to maintain sustained acid rain solution contact.
  • After 400 hours of exposure, visual assessments are performed, with damage rated on a defined scale from 0 (no damage) to 10 (severe etching and discoloration).
  • The standard includes detailed evaluation criteria and pictorial evidence for consistent assessment by trained and untrained assessors.
• Significance and Use: Acid etch resistance is a critical parameter for automotive exterior coatings and a key concern for warranty claims in the automotive industry. This test method provides a way to consistently reproduce and evaluate acid etch damage observed in real-world conditions, enabling quality assurance and product development for automotive coatings.

Applications

• Automotive OEMs and Coating Manufacturers: The test is used to qualify new clearcoat formulations, benchmark products, and inform warranty coverage by providing reliable accelerated assessments of acid etch performance.
• Quality Control and Research: Laboratories use this standard for comparative testing of coating systems and to simulate effects of acid rain on coating durability, aiding in the development of more resistant formulations.
• Third-party Testing Laboratories: Provides a consistent, well-documented method for contract testing services to evaluate acid rain resistance of automotive coatings.
• Technical Documentation and Warranty Support: Results from this standard support the documentation needed for product claims, customer communications, and compliance with manufacturer specifications.

Related Standards

• ASTM G155: Practice for Operating Xenon Arc Light Apparatus for Exposure of Non-Metallic Materials. This standard defines requirements for the xenon-arc exposure device used in ASTM D7356/D7356M-19.
• ASTM D1293: Test Methods for pH of Water, relevant for preparing the simulated acid rain solution.
• ASTM D4517: Test Method for Low-Level Total Silica in High Purity Water, used for ensuring water purity during testing.
• ASTM G113 & G147: Provide terminology and procedures for handling of nonmetallic materials in weathering tests.
• ASTM G151: Practice for Exposing Nonmetallic Materials in Accelerated Test Devices, referenced for general accelerated weathering protocols.

Note: As of this edition, there is no known ISO equivalent to ASTM D7356/D7356M-19, making it a unique reference for acid etch resistance testing of automotive clearcoats.

Practical Value

Implementing ASTM D7356/D7356M-19 ensures accurate simulation of real-world acid rain effects on automotive clearcoats, supporting paint technology innovation, product reliability, and reduction of warranty claims. By aligning with this test method, manufacturers and suppliers benefit from year-round, reproducible testing using a standardized approach, enhancing product quality and customer satisfaction in the automotive coatings market.

Keywords: ASTM D7356, acid etch resistance, automotive clearcoats, xenon-arc exposure, accelerated weathering, acid rain, coating durability, automotive coatings standard.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7356/D7356M − 19
Standard Test Method for
Accelerated Acid Etch Weathering of Automotive Clearcoats
Using a Xenon-Arc Exposure Device
This standard is issued under the fixed designation D7356/D7356M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* 1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This test method covers an accelerated exposure test
responsibility of the user of this standard to establish appro-
intendedtosimulatedefectsinautomotiveclearcoatscausedby
priate safety, health, and environmental practices and deter-
acid rain that occur at the Jacksonville, Florida exposure site.
mine the applicability of regulatory limitations prior to use.
Exterior exposures at an acid rain test location in Jacksonville,
1.6 This international standard was developed in accor-
Florida produce etch defects that range from small pits to 12.7
dance with internationally recognized principles on standard-
mm [0.5 in.] in diameter or larger acid-etched spots. The latter
ization established in the Decision on Principles for the
type of defect is not produced in other acid-etch tests that only
Development of International Standards, Guides and Recom-
produce pits that are smaller than 6.35 mm [0.25 in.] in
mendations issued by the World Trade Organization Technical
diameter.
Barriers to Trade (TBT) Committee.
NOTE 1—Digital images of the acid etch defects produced in outdoor
acid-rain exposures and in the accelerated test described in this test
2. Referenced Documents
method are found in Appendix X1.
2.1 ASTM Standards:
1.2 The accelerated test described in this test method uses a
D1293 Test Methods for pH of Water
xenon-arc light source with daylight filter conforming to the
D4517 Test Method for Low-Level Total Silica in High-
requirements of Practice G155. Specimens are sprayed with a
Purity Water by Flameless Atomic Absorption Spectros-
simulated acid rain solution and requires the use of a
copy
horizontal, flat specimen array in order to allow the acid rain
G113 Terminology Relating to Natural andArtificial Weath-
solution to remain on the test specimens for an extended period
ering Tests of Nonmetallic Materials
of time.
G147 Practice for Conditioning and Handling of Nonmetal-
1.3 There is no known ISO equivalent to this test method.
lic Materials for Natural and Artificial Weathering Tests
G151 Practice for Exposing Nonmetallic Materials inAccel-
1.4 The values stated in either SI units or inch-pound units
erated Test Devices that Use Laboratory Light Sources
are to be regarded separately as standard. The values stated in
G155 Practice for Operating XenonArc LightApparatus for
each system are not necessarily exact equivalents; therefore, to
Exposure of Non-Metallic Materials
ensure conformance with the standard, each system shall be
used independently of the other, and values from the two
3. Terminology
systems shall not be combined.
3.1 Definitions—Definitions applicable to this standard can
be found in Terminology G113.
This test method is under the jurisdiction of ASTM Committee D01 on Paint
3.2 Definitions of Terms Specific to This Standard:
and Related Coatings, Materials, andApplications and is the direct responsibility of
3.2.1 acid rain, n—cloud or rain droplets containing
Subcommittee D01.27 on Accelerated Testing.
pollutants, such as oxides of sulfur and nitrogen, to make them
Current edition approved Nov. 15, 2019. Published November 2019. Originally
approved in 2007. Last previous edition approved in 2013 as D7359 – 13. DOI: acidic.
10.1520/D7356_D7356M-19.
3.2.2 acid rain spots, n—spots are produced when the sun
The acid etch test method is covered by a patent. Interested parties are invited
evaporates standing water on the vehicle’s surface.
to submit information regarding the identification of an alternative(s) to this
patented item to ASTM International Headquarters. Your comments will receive
careful considerations at a meeting of the responsible technical committee, which
you may attend.
3 4
Brennan, P. J, Marino, M., Boisseau, J. and Campbell, D., Accelerated Acid For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Etch, Part II: Refined Test Procedure to ReproduceAutomotiveAcid Etch Provides contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Improved Lab Practicality and Proven Correlation, FSCT, 2006 FutureCoat Pro- Standards volume information, refer to the standard’s Document Summary page on
ceedings. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7356/D7356M − 19
3.2.2.1 Discussion—They fall into two categories, mineral 6.1.2.1 The volume of spray water shall be sufficient to
deposits and acid-etched spots. Mineral deposits are white flood (with excess) the surface of the specimen within the
calcium spots or salt deposits left on the surface after water one-minutespraytime.Aspraydeliveryrateof3L/min/m has
evaporates. These deposits can be easily removed with a been found suitable.
pre-wax cleaner (polish) or a clay bar. Acid-etched spots are 6.1.3 Useofasinglespraysystemhasnotbeenevaluated.If
depressions in the paint or clear coat, which cannot be easily a single spray system is used, the following shall be included
removed. with the test report:
6.1.3.1 If a single spray system is used for both the acid
3.2.3 trained assessor, n—an individual knowledgeable and
solution and high purity water, data verifying that there is no
proficient in the procedure capable of making consistent
cross contamination between the acid spray and the high purity
evaluations based on defined criteria so as to produce a
water spray.
repeatable result.
6.1.4 Xenon-arc apparatus shall be equipped with daylight
3.2.3.1 Discussion—In this standard, assessor discerns the
filters that meet the requirements of Practice G155.
difference between water spotting and etching, and judges the
6.1.5 Xenon-arc apparatus shall be able to simultaneously
magnitude.
and automatically control irradiance, black panel temperature,
relative humidity and chamber air temperature.
4. Summary of Test Method
6.2 Xenon-arc apparatus shall be equipped with an uninsu-
4.1 The Automotive Clearcoat coating being evaluated is
lated black panel complying with Practice G151.
applied to an automotive basecoat (typically black) that has
beencoatedontoasteelpanel.Alledgesofthepanelaresealed
6.3 pH meter capable of measuring to 60.2 units.
to prevent corrosion. Coatings applied to other types of panels
7. Reagents and Materials
may also be used.
4.2 Test specimens are placed in a xenon-arc device 7.1 0.02 N H SO Sulfuric Acid Volumetric Solution, (accu-
2 4
rate to 61 part per 1000).
equipped with a horizontal exposure rack and are exposed to
alternating periods of light, spray with acid rain solution, and
7.2 0.3 % HNO (Nitric Acid), by weight or v/v.
spray with water. The evaporation of the water from the acid
7.3 0.02 N NaOH Sodium Hydroxide Volumetric Solution,
solution on the test specimen surface results in deposits with
(accurate to 6 1 part per 1000).
high acid concentration.
7.4 0.01 M CaCl , (Calcium Chloride Standard for water
4.3 After 400 hr of exposure, test specimens are evaluated
hardness testing).
and rated for etch.
7.5 0.01 M KCl (Potassium Chloride) Conductivity
5. Significance and Use
Solution, calibration standard solution 1413 µΩ.
5.1 Acid etch damage is an important warranty claim item
8. Apparatus Setup
for automotive companies. As a result, acid etch resistance is
8.1 Operate, maintain and calibrate the apparatus to manu-
an important parameter for automotive exterior coatings. The
facturer’s specifications. To the extent possible, perform all
method described in this test method has been shown to
calibrations and maintenance before the test starts or after the
simulate acid etch damage of automotive clearcoats that occurs
test has been completed. If the test is interrupted for any reason
when such coatings are exposed from May through mid-
3,5
(excluding daily specimen repositioning), it may affect test
August in Jacksonville, FL. The accelerated test described in
results and as such, the reason for the interruption and its
this standard allows year-round testing as opposed to the
duration shall be noted on the test report.
limited outdoor exposure time available for the Jacksonville,
FL exposures.
8.2 Water used for spray and humidification shall have a
maximum of 1 ppm total solids and a maximum of 0.2 ppm
6. Apparatus
silica. Unless otherwise specified, determine silica levels in
6.1 Xenon-arc exposure device conforming to Practice
accordance with Practice D4517. A combination of deioniza-
G151 and Practice G155 with the following additional require- tion and reverse osmosis treatment can effectively produce
ments.
water with the desired purity.
6.1.1 Specimen rack that is within 63° of horizontal.
8.3 Acid Rain Solution—The composition for the acid rain
6.1.2 Means to spray pure deionized water and acid rain
solution is as follows:
solutions independently, and without cross contamination,
8.3.1 Add 977.5 g of deionized water toa1Lflask and then
from one another.
add the following:
15.0 g – 0.02 N H SO (Sulphuric Acid)
NOTE 2—Use of dual spray systems, one for acid solution and the other
2 4
for high purity water has been found to be effective for eliminating cross
2.2 g – 0.3 % HNO (Nitric Acid)
contamination.
2.5 g – 0.02 N NaOH (Sodium Hydroxide)
1.8 g – 0.01 M CaCl (Calcium Chloride)
1.0 g – 0.01 M KCl (Potassium Chloride)
Boisseau, J. and Pattison, L., BASF Corporation, and Henderson, K. and Hunt,
8.3.2 This provides a 1000 g [1 L] solution with a pH of 3.3
R., Bayer Material Science, “The Flaws in Accelerated Weathering of Automotive
OEM Coatings,” Paint and Coatings Industry, June 2006. to 3.5, which is similar to that of Jacksonville rain water.
D
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7356/D7356M − 13 D7356/D7356M − 19
Standard Test Method for
Accelerated Acid Etch Weathering of Automotive Clearcoats
Using a Xenon-Arc Exposure Device
This standard is issued under the fixed designation D7356/D7356M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This test method covers an accelerated exposure test intended to simulate defects in automotive clearcoats caused by acid
rain that occur at the Jacksonville, Florida exposure site. Exterior exposures at an acid rain test location in Jacksonville, Florida
produce etch defects that range from small pits to 12.7 mm [0.5 in.] in diameter or larger acid-etched spots. The latter type of defect
is not produced in other acid-etch tests that only produce pits that are smaller than 6.35 mm [0.25 in.] in diameter.
NOTE 1—Digital images of the acid etch defects produced in outdoor acid-rain exposures and in the accelerated test described in this test method are
found in Appendix X1.
1.2 The accelerated test described in this test method uses a xenon-arc light source with daylight filter conforming to the
requirements of Practice G155. Specimens are sprayed with a simulated acid rain solution and requires the use of a horizontal, flat
specimen array in order to allow the acid rain solution to remain on the test specimens for an extended period of time.
1.3 There is no known ISO equivalent to this test method.
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used
independently of the other, and values from the two systems shall not be combined.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D1293 Test Methods for pH of Water
D4517 Test Method for Low-Level Total Silica in High-Purity Water by Flameless Atomic Absorption Spectroscopy
G113 Terminology Relating to Natural and Artificial Weathering Tests of Nonmetallic Materials
G147 Practice for Conditioning and Handling of Nonmetallic Materials for Natural and Artificial Weathering Tests
G151 Practice for Exposing Nonmetallic Materials in Accelerated Test Devices that Use Laboratory Light Sources
G155 Practice for Operating Xenon Arc Light Apparatus for Exposure of Non-Metallic Materials
3. Terminology
3.1 Definitions—Definitions applicable to this standard can be found in Terminology G113.
3.2 Definitions of Terms Specific to This Standard:
This test method is under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings, Materials, and Applications and is the direct responsibility of
Subcommittee D01.27 on Accelerated Testing.
Current edition approved June 1, 2013Nov. 15, 2019. Published September 2013November 2019. Originally approved in 2007. Last previous edition approved in 20072013
as D7359D7359 – 13. – 07. DOI: 10.1520/D7356_D7356M-13.10.1520/D7356_D7356M-19.
The acid etch test method is covered by a patent. Interested parties are invited to submit information regarding the identification of an alternative(s) to this patented item
to ASTM International Headquarters. Your comments will receive careful considerations at a meeting of the responsible technical committee, which you may attend.
Brennan, P. J, Marino, M., Boisseau, J. and Campbell, D., Accelerated Acid Etch, Part II: Refined Test Procedure to Reproduce Automotive Acid Etch Provides Improved
Lab Practicality and Proven Correlation, FSCT, 2006 FutureCoat Proceedings.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7356/D7356M − 19
3.2.1 acid rain, n—cloud or rain droplets containing pollutants, such as oxides of sulfur and nitrogen, to make them acidic.
3.2.2 acid rain spots, n—spots are produced when the sun evaporates standing water on the vehicle’s surface.
3.2.2.1 Discussion—
They fall into two categories, mineral deposits and acid-etched spots. Mineral deposits are white calcium spots or salt deposits left
on the surface after water evaporates. These deposits can be easily removed with a pre-wax cleaner (polish) or a clay bar.
Acid-etched spots are depressions in the paint or clear coat, which cannot be easily removed.
3.2.3 trained assessor, n—an individual knowledgeable and proficient in the procedure capable of making consistent evaluations
based on defined criteria so as to produce a repeatable result.
3.2.3.1 Discussion—
In this standard, assessor discerns the difference between water spotting and etching, and judges the magnitude.
4. Summary of Test Method
4.1 The Automotive Clearcoat coating being evaluated is applied to an automotive basecoat (typically black) that has been
coated onto a steel panel. All edges of the panel are sealed to prevent corrosion. Coatings applied to other types of panels may also
be used.
4.2 Test specimens are placed in a xenon-arc device equipped with a horizontal exposure rack and are exposed to alternating
periods of light, spray with acid rain solution, and spray with water. The evaporation of the water from the acid solution on the
test specimen surface results in deposits with high acid concentration.
4.3 After 400 hourshr of exposure, test specimens are evaluated and rated for etch.
5. Significance and Use
5.1 Acid etch damage is an important warranty claim item for automotive companies. As a result, acid etch resistance is an
important parameter for automotive exterior coatings. The method described in this test method has been shown to simulate acid
etch damage of automotive clearcoats that occurs when such coatings are exposed from May through mid-August in Jacksonville,
3,5
FL. The accelerated test described in this standard allows year-round testing as opposed to the limited outdoor exposure time
available for the Jacksonville, FL exposures.
6. Apparatus
6.1 Xenon-arc exposure device conforming to Practice G151 and Practice G155 with the following additional requirements.
6.1.1 Specimen rack that is within 63 degrees 63° of horizontal.
6.1.2 Means to spray pure deionized water and acid rain solutions independently, and without cross contamination, from one
another.
NOTE 2—Use of dual spray systems, one for acid solution and the other for high purity water has been found to be effective for eliminating cross
contamination.
6.1.2.1 The volume of spray water shall be sufficient to flood (with excess) the surface of the specimen within the one-minute
spray time. A spray delivery rate of 3 litresL/min/m per minute per square metre has been found suitable.
6.1.3 Use of a single spray system has not been evaluated. If a single spray system is used, the following shall be included with
the test report:
6.1.3.1 If a single spray system is used for both the acid solution and high purity water, data verifying that there is no cross
contamination between the acid spray and the high purity water spray.
6.1.4 Xenon-arc apparatus shall be equipped with daylight filters that meet the requirements of Practice G155.
6.1.5 Xenon-arc apparatus shall be able to simultaneously and automatically control irradiance, black panel temperature,
relative humidity and chamber air temperature.
6.2 Xenon-arc apparatus shall be equipped with an uninsulated black panel complying with Practice G151.
6.3 pH meter capable of measuring to 60.2 units.
7. Reagents and Materials
7.1 0.02 N H SO Sulfuric Acid Volumetric Solution, (accurate to 61 part per 1000).
2 4
7.2 0.3 % HNO (Nitric Acid), by weight or v/v.
Boisseau, J. and Pattison, L., BASF Corporation, and Henderson, K. and Hunt, R., Bayer Material Science, “The Flaws in Accelerated Weathering of Automotive OEM
Coatings,” Paint and Coatings Industry, June 2006.
D7356/D7356M − 19
7.3 0.02 N NaOH Sodium Hydroxide Volumetric Solution, (accurate to 6 1 part per 1000).
7.4 0.01 M CaCl , (Calcium Chloride Standard for water hardness testing).
7.5 0.01 M KCl (Potassium Chloride) Conductivity Solution, calibration standard solution 1413 micro-ohms.μΩ.
8. Apparatus Setup
8.1 Operate, maintain and calibrate the apparatus to manufacturer’s specifications. The test should not be interrupted once it has
started (excluding daily panel reposition). Calibrations and maintenance should be completed To the extent possible, perform all
calibrations and maintenance before the test starts or after the test has completed.been completed. If the test is interrupted for any
reason (excluding daily specimen repositioning), it may affect test results and as such, the reason for the interruption and its
duration shall be noted on the test report.
8.2 Water used for spray and humidification shall have a maximum of 1 ppm total solids and a maximum of 0.2 ppm silica.
Unless otherwise specified, determine silica levels in accordance with Practice D4517. A combination of deionization and reverse
osmosis treatment can effectively produce water with the desired purity.
8.3 Acid Rain Solution—The composition for the acid rain solution is as follows:
8.3.1 Add 977.5 g of deionized water to a 1 litreL flask and then add the following:
15.0 gramsg – 0.02 N H SO (Sulphuric Acid)
2 4
2.2 gramsg – 0.3 % HNO (Nitric Acid)
2.5 gramsg – 0.02 N NaOH (Sodium Hydroxide)
1.8 gramsg – 0.01 M CaCl (Calcium Chloride)
1.0 gramsg – 0.01 M KCl (Potassium Chloride)
8.3.2 This provides a 1000 g (1 L)[1 L] solution with a pH of 3.3 to 3.5, which is similar to that of Jacksonville rain water.
TABLE 1 Accelerated Acid Etch Exposure Cycle Sequence
Accelerated Acid Test Exposure Cycle
Step 1 1 min Dark exposure; with acid rain spray
Step 2 3 hr 50 min Dark exposure; 40°C uninsulated black panel (B.P.) temperature (monitored not controlled); 40°C chamber air
temperature; 80 % RH
Step 3 12 hr Light exposure; 0.55 W/m /nm at 340 nm; daylight filters; 65°C uninsulated B.P.; 50°C chamber air temperature; 80 %
RH
Step 4 27 min Dark exposure; 40°C uninsulated B.P. temperature (monitored not cont
...