ASTM G85-19

Standard Practice for Modified Salt Spray (Fog) Testing

SIGNIFICANCE AND USE
3.1 This practice is applicable to ferrous and nonferrous metals; also organic and inorganic coatings. The variations described herein are useful when a different or more corrosive environment than the salt fog described in Practice B117 is desired.
SCOPE
1.1 This practice covers and sets forth conditions for five modifications in salt spray (fog) testing for specification purposes. These are in chronological order of their development:  
1.1.1 Annex A1,  acetic acid-salt spray test, continuous.  
1.1.2 Annex A2,  cyclic acidified salt spray test.  
1.1.3 Annex A3,  seawater acidified test, cyclic (SWAAT).  
1.1.4 Annex A4,  SO2 salt spray test, cyclic.  
1.1.5 Annex A5,  dilute electrolyte cyclic fog dry test.  
1.2 This practice does not prescribe the type of modification, test specimen or exposure periods to be used for a specific product, nor the interpretation to be given to the results.  
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.4 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.  
1.5 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: 31-Oct-2019
• ICS: 77.060 - Corrosion of metals
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.05 - Laboratory Corrosion Tests

Relations

• Replaces: ASTM G85-11 - Standard Practice for Modified Salt Spray (Fog) Testing
• Effective Date: 01-Nov-2019
• Refers: ASTM E70-24 - Standard Test Method for pH of Aqueous Solutions With the Glass Electrode
• Effective Date: 01-Jan-2024
• Refers: ASTM D1654-08(2016) - Standard Test Method for Evaluation of Painted or Coated Specimens Subjected to Corrosive Environments
• Effective Date: 01-Dec-2016
• Refers: ASTM E70-07(2015) - Standard Test Method for pH of Aqueous Solutions With the Glass Electrode
• Effective Date: 01-Jun-2015
• Refers: ASTM D609-00(2012) - Standard Practice for Preparation of Cold-Rolled Steel Panels for Testing Paint, Varnish, Conversion Coatings, and Related Coating Products
• Effective Date: 01-Jun-2012
• Refers: ASTM B117-11 - Standard Practice for Operating Salt Spray (Fog) Apparatus
• Effective Date: 01-Oct-2011
• Refers: ASTM B117-09 - Standard Practice for Operating Salt Spray (Fog) Apparatus
• Effective Date: 01-Jul-2009
• Refers: ASTM D1654-08 - Standard Test Method for Evaluation of Painted or Coated Specimens Subjected to Corrosive Environments
• Effective Date: 01-Nov-2008
• Refers: ASTM D1141-98(2008) - Standard Practice for the Preparation of Substitute Ocean Water
• Effective Date: 15-Jul-2008
• Refers: ASTM B117-07a - Standard Practice for Operating Salt Spray (Fog) Apparatus
• Effective Date: 15-Dec-2007
• Refers: ASTM B117-07 - Standard Practice for Operating Salt Spray (Fog) Apparatus
• Effective Date: 01-Mar-2007
• Refers: ASTM D609-00(2006) - Standard Practice for Preparation of Cold-Rolled Steel Panels for Testing Paint, Varnish, Conversion Coatings, and Related Coating Products
• Effective Date: 01-Nov-2006
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006
• Refers: ASTM D1654-05 - Standard Test Method for Evaluation of Painted or Coated Specimens Subjected to Corrosive Environments
• Effective Date: 01-Mar-2005
• Refers: ASTM B117-03 - Standard Practice for Operating Salt Spray (Fog) Apparatus
• Effective Date: 01-Oct-2003

Overview

ASTM G85-19: Standard Practice for Modified Salt Spray (Fog) Testing is a key international standard published by ASTM International. This practice provides guidance for laboratory-based corrosion testing using modified salt spray (fog) methods. The main aim is to simulate environments more aggressive or different from those described in ASTM B117, allowing for tailored accelerated corrosion testing of metals, as well as organic and inorganic coatings. ASTM G85-19 is recognized in quality assurance programs and product specifications for both ferrous and nonferrous materials and coatings, widening its application across industries such as automotive, aerospace, marine, and construction.

Key Topics

• Applicability: Relevant for testing the corrosion resistance of ferrous and nonferrous metals, and organic/inorganic coatings.
• Test Variations Covered: The standard specifies five primary modifications in salt spray testing:
  • Annex A1: Acetic acid-salt spray test (continuous)
  • Annex A2: Cyclic acidified salt spray test
  • Annex A3: Seawater acidified test, cyclic (SWAAT)
  • Annex A4: SO₂ salt spray test, cyclic
  • Annex A5: Dilute electrolyte cyclic fog dry test
• Test Apparatus: Requirements for fog chambers, salt solution reservoirs, air supply, and temperature control to maintain test integrity.
• Specimen Preparation: Clear guidelines for cleaning, handling, and protecting test specimens, ensuring accurate and reproducible results.
• Test Operation: Details on specimen positioning, maintenance of fog conditions, collection of fog solution, and continuity of test cycles.
• Evaluation and Reporting: Procedures for examining specimens, documenting test conditions, and reporting data such as solution pH, salt solution concentration, test duration, and observed results.

Applications

ASTM G85-19 is valued for its ability to simulate a range of corrosive atmospheres, offering practical benefits in the following areas:

• Material Qualification: Assessing the corrosion resistance of new alloys or coatings before use in demanding environments.
• Product Development: Evaluating the performance of protective coatings, surface treatments, and finishes for metals to ensure durability and longevity.
• Quality Control: Using standardized test conditions to verify as-manufactured products meet required corrosion protection standards.
• Comparative Testing: Comparing the efficacy of different coatings, surface treatments, or material grades under defined accelerated conditions.
• Research & Development: Supporting studies of corrosion mechanisms and the influence of environmental variables on material degradation.

Industries such as automotive, aerospace, marine, and infrastructure rely on ASTM G85-19 to ensure materials and coatings withstand real-world exposure, contributing to safety, performance, and extended service life.

Related Standards

To ensure comprehensive corrosion testing, ASTM G85-19 should be considered alongside these related international standards:

• ASTM B117 - Standard Practice for Operating Salt Spray (Fog) Apparatus
• ASTM D609 - Preparation of Cold-Rolled Steel Panels for Testing Paints and Coatings
• ASTM D1141 - Preparation of Substitute Ocean Water
• ASTM D1193 - Specification for Reagent Water
• ASTM D1654 - Evaluation of Painted or Coated Specimens Subjected to Corrosive Environments
• ASTM E70 - pH Measurement of Aqueous Solutions with a Glass Electrode

By referencing ASTM G85-19 along with these related documents, laboratories and quality programs can ensure robust, internationally aligned corrosion testing methodologies.

Keywords: ASTM G85-19, modified salt spray, fog testing, corrosion testing, accelerated corrosion, cyclic corrosion, seawater acidified test, SO₂ salt spray, coatings testing, laboratory corrosion test, international 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:G85 −19
Standard Practice for
Modified Salt Spray (Fog) Testing
ThisstandardisissuedunderthefixeddesignationG85;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope D609Practice for Preparation of Cold-Rolled Steel Panels
for Testing Paint, Varnish, Conversion Coatings, and
1.1 This practice covers and sets forth conditions for five
Related Coating Products
modifications in salt spray (fog) testing for specification
D1141Practice for the Preparation of Substitute Ocean
purposes. These are in chronological order of their develop-
Water
ment:
D1193Specification for Reagent Water
1.1.1 Annex A1, acetic acid-salt spray test, continuous.
D1654Test Method for Evaluation of Painted or Coated
1.1.2 Annex A2, cyclic acidified salt spray test.
Specimens Subjected to Corrosive Environments
1.1.3 Annex A3, seawater acidified test, cyclic (SWAAT).
E70Test Method for pH of Aqueous Solutions With the
1.1.4 Annex A4, SO salt spray test, cyclic.
Glass Electrode
1.1.5 Annex A5, dilute electrolyte cyclic fog dry test.
1.2 This practice does not prescribe the type of
3. Significance and Use
modification, test specimen or exposure periods to be used for
a specific product, nor the interpretation to be given to the
3.1 This practice is applicable to ferrous and nonferrous
results.
metals; also organic and inorganic coatings. The variations
described herein are useful when a different or more corrosive
1.3 The values stated in SI units are to be regarded as
environment than the salt fog described in Practice B117 is
standard. The values given in parentheses after SI units are
desired.
provided for information only and are not considered standard.
1.4 This standard does not purport to address all of the
4. Apparatus
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4.1 Cabinet:
priate safety, health, and environmental practices and deter-
4.1.1 The apparatus required for salt spray (fog) testing
mine the applicability of regulatory limitations prior to use.
consists of a fog chamber, a salt solution reservoir, a supply of
1.5 This international standard was developed in accor-
suitably conditioned compressed air, one or more atomizing
dance with internationally recognized principles on standard-
nozzles,specimensupports,provisionforheatingthechamber,
ization established in the Decision on Principles for the
and necessary means of control. The size and detailed con-
Development of International Standards, Guides and Recom-
struction of the cabinet are optional, provided the conditions
mendations issued by the World Trade Organization Technical
obtainedmeettherequirementsofthispractice.Thematerialof
Barriers to Trade (TBT) Committee.
construction shall be such that it will not affect the corrosive-
2. Referenced Documents ness of the fog. Suitable apparatus that may be used to obtain
2 these conditions is described inAppendix X1 of Practice B117
2.1 ASTM Standards:
with necessary modifications described in each annex of this
B117Practice for Operating Salt Spray (Fog) Apparatus
practice.
4.1.2 Design the cabinet so that drops of solution that
This practice is under the jurisdiction ofASTM Committee G01 on Corrosion
of Metals and is the direct responsibility of Subcommittee G01.05 on Laboratory accumulate on the ceiling or cover of the chamber do not fall
Corrosion Tests.
on the specimens being tested. Do not return drops of solution
Current edition approved Nov. 1, 2019. Published December 2019. Originally
that fall from the specimens to the solution reservoir for
approved in 1985. Last previous edition approved in 2011 as G85–11. DOI:
respraying.
10.1520/G0085–19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4.1.3 Equip the cabinet with one or more timing devices to
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
provide for intermittent spraying or periodic introduction of a
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. gas, or both.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G85−19
4.2 Air Supply: solution for the chemical cleaning, or passivation, of stainless
4.2.1 Make sure the compressed air supply to the nozzle or steel specimens is permissible when agreed upon between the
nozzlesforatomizingthesaltsolutionisfreeofoilanddirtand purchaser and the seller. Take care that specimens are not
maintain the air supply between 69 and 172 kPa (10 and 25 recontaminated after cleaning by excessive or careless han-
psi). dling.
5.2.2 Prepare specimens for evaluation of paints and other
NOTE 1—The air supply may be freed of oil and dirt by passing it
organic coatings in accordance with applicable specification(s)
through a water scrubber or at least 610 mm (2 ft) of suitable cleaning
for the material(s) being tested, or as agreed upon between the
material such as asbestos, sheep’s wool, or activated alumina.
purchaser and supplier. Otherwise, make sure the test speci-
4.2.2 Temperature in the saturator tower (bubble tower)
mens consist of steel meeting the requirements of Practice
varies depending on the test method used.
D609; clean and prepare the specimens for coating in accor-
4.3 Conditions in Salt-Spray Chamber:
dance with applicable procedure of Practice D609.
4.3.1 Temperature—The temperature in the exposure zone
5.2.3 Whenever it is desired to determine the development
varies with the test method used. For recommended exposure
of corrosion from an abraded area in the paint or organic
zone temperatures for the various methods, see the annexes in
coating,makeascratchorscribedlinethroughthecoatingwith
this practice. Each set point and its tolerance represents an
a sharp instrument so that the underlying metal is exposed
operational control point for equilibrium conditions at a single
before testing. Use the conditions of making the scratch as
locationinthecabinetwhichmaynotnecessarilyrepresentthe
defined in Test Method D1654, unless otherwise agreed upon
uniformity of conditions throughout the cabinet. Record the
between the purchaser and seller.
temperature within the exposure zone of the closed cabinet at
5.2.4 Protect the cut edges of plated, coated, or duplex
least twice a day at least 7 h apart (except on weekends and
materialsandareasthatcontainidentificationmarksorthatare
holidays, when the salt spray test is not interrupted for
incontactwiththeracksorsupportswithasuitablecoatingthat
exposing, rearranging, or removing test specimens or to check
is stable under the conditions of the test, such as ceresin wax,
and replenish the solution in the reservoir).
unless otherwise specified.
NOTE 2—Suitable methods to record the temperature are a continuous
NOTE4—Shoulditbedesirabletocuttestspecimensfrompartsorfrom
recording device or a thermometer which can be read from outside the
preplated, painted, or otherwise coated-steel sheet, protect the cut edges
closed cabinet. Obtain the recorded temperature with the salt spray
by coating them with paint, wax, tape, or other effective media so that the
chamber closed to avoid a false low reading because of wet-bulb effect
developmentofpreferentialattackoragalvaniceffectbetweensuchedges
when the chamber is open.
and the adjacent plated or otherwise coated-metal surfaces, is prevented.
4.3.2 Atomization and Quantity of Fog—Place at least two
6. Salt Solutions
clean fog collectors within the exposure zone so that no drops
6.1 Makethesaltsolutionsbyusingeithersyntheticseasalt
of solution from the test specimens or any other source can be
in accordance with Practice D1141 or sodium chloride in
collected. Position the collectors in the proximity of the test
accordance with Practice B117, unless otherwise specified in
specimens, one nearest to any nozzle and the other farthest
the appropriate annex. Make-up water shall be distilled or
fromallnozzles.Makesurethatforeach80cm ofhorizontal-
collecting area fog accumulates in each collector from 1.0 to deionized water conforming to Type IV water in Specification
D1193 (except that for this practice, limits for chlorides and
2.0 mLof solution per hour based on an average run of at least
16 h continuous spray. sodium may be ignored).
6.2 Synthetic Sea Salt Solution (see Annex A3)—Make the
NOTE 3—Suitable collecting devices are glass funnels with the stems
inserted through stoppers into graduated cylinders or crystallizing dishes.
salt solution so that it consists of 42 g of synthetic sea salt in
Funnels and dishes with a diameter of 100 mm have an area of about 80
accordance with Practice D1141 per litre of solution (see Note
cm .
5).
4.3.3 Direct or baffle the nozzle or nozzles so that none of
6.3 SodiumChlorideSolution(ExceptAnnexA3andAnnex
the spray can impinge directly on the test specimens.
A5): Prepare the salt solution by dissolving 5 6 1 parts by
weight of sodium chloride in 95 parts of water conforming to
5. Test Specimens
Type IV water in Specification D1193 (except that for this
5.1 Definethetypeandnumberoftestspecimenstobeused,
practice, limits for chlorides and sodium may be ignored)
aswellasthecriteriafortheevaluationofthetestresultsinthe
containing not more than 200 ppm of total solids (see Note 5).
specifications covering the material or product being tested or
Halides (Bromide, Fluoride, and Iodide) other than Chloride
upon mutual agreement between the purchaser and the seller.
shall constitute less than 0.1 % by mass of the salt content.
5.2 Preparation of Test Specimens: Copper content shall be less than 0.3 ppm by mass. Sodium
5.2.1 Clean metallic and metallic-coated specimens. The chloridethathashadanti-cakingagentsaddedshallnotbeused
cleaning method is optional depending on the nature of the because such agents may act as corrosion inhibitors (see Note
surface and the contaminants; however, when using a cleaning 6).SeeTable1foralistingoftheseimpurityrestrictions.Upon
method do not include in the contents abrasives other than a agreement between the purchaser and the seller, analysis may
paste of pure magnesium oxide nor of solvents which may be required and limits established for elements or compounds
form corrosive or inhibitive films. The use of nitric acid not specified in the chemical composition given above.
G85−19
TABLE 1 Maximum Allowable Limits for Impurity Levels in
7.1.2 Do not allow contact of the specimens between each
Sodium Chloride
other, between any metallic material, or between any material
Impurity Description Allowable Amount
capable of acting as a wick.
Total Impurities #0.3%
7.1.3 Placeeachspecimensoastopermitfreesettlingoffog
Halides (Bromide, Fluoride and Iodide) <0.1 %
excluding Chloride on all specimens. A minimum spacing between specimens of
Copper <0.3 ppm
30 mm is recommended.
Anti-caking Agents None Added
7.1.4 Do not permit the salt solution from one specimen to
drip on any other specimen.
7.1.5 It is recommended that placement of replicate speci-
NOTE 5—The specific gravity of salt solution will change with
mens be randomized to avoid possible bias caused by differ-
temperature.Table2showssaltconcentrationanddensityversustempera-
ence in spray patterns. Individual specimens may also be
ture and can be used to determine if the sample measured is within
specification.Thesampletobemeasuredmaybeacompositesamplefrom rotated daily for the same reason.
multiple fog-collecting devices within a single cabinet, if necessary, to
7.1.6 Suitable materials for the construction or coating of
obtain sufficient solution volume for measurement.
racks and supports are glass, rubber, plastic, or suitably coated
Table 2 shows the salt concentration and salt density of 4%, 5%, and
wood. Do not use bare metal. Support specimens preferably
6% salt solution between 20 and 40°C.Ameasurement that falls within
the range between 4 and 6% is acceptable.
fromthebottomortheside.Slottedwooden,laminatedplastic,
It is important to understand the equipment being used to measure
or inert plastic strips are suitable for the support of flat panels.
specificgravity.Onecommonpracticeforspecificgravitymeasurementis
Suspension from glass hooks or waxed string may be used as
the use of a hydrometer. If used, careful attention to the hydrometer type
longasthespecifiedpositionofthespecimensisobtained,and,
is important as most are manufactured and calibrated for measurements at
15.6°C. Since salt density is temperature dependent an offset will be
if necessary, by means of secondary support at the bottom of
necessary to make an accurate measurement at other temperatures.
the specimens.
Contact the hydrometer manufacturer to find the proper offset for the
hydrometer being used.
7.2 Continuity of Test—Unless otherwise specified in the
NOTE6—Ameasurablelimitforanti-cakingagentsisnotbeingdefined
specificationscoveringthematerialorproductbeingtested,the
as a result of how salt is manufactured. During salt manufacturing, it is
test shall be continuous for the duration of the entire test
common practice to create salt slurry from the raw salt mined. A
crystallization process then captures the pure salt from this slurry. Some period. Continuous operation implies that the chamber be
naturally occurring anti-caking agents can be formed in this process and
closed except for the short daily interruptions necessary to
are not removed from the resultant product. Avoid salt products where
inspect, rearrange, or remove test specimens, to check and
extraanti-cakingagentsareadded.Additionally,whendoinganelemental
replenish the solution in the reservoir, and to make necessary
analysis of salt there can be trace elements present that either stand alone
orarepartofananti-cakingagent.Itisnoteconomicallyfeasibletoknow
recordings as described in 4.3.1, 4.3.2, and Section 9. (See
wheresuchelementscamefromduetothelonglistofpossibleanti-caking
Note 8.)
agentsthatwouldhavetobetested.Thereforeasaltproductthatmeetsthe
impurity, halide, and copper limits with no anti-caking agents added is
NOTE 8—Operations should be so scheduled that the cumulative
acceptable. The salt supplier can provide an analysis of the salt with a
maximum time for these interruptions are held to 60 min or less per day.
statementindicatingthatanti-cakingagentswerenotaddedtotheproduct.
It is recommended to have only one interruption per day if possible. If
interruptiontimeislongerthat60min,itshouldbenotedinthetestreport.
6.4 The pH of the salt solutions will vary depending on the
test method used. Before the solution is atomized, free it of
7.3 Period of Test—Designate the period of test in accor-
suspended solids (see Note 7). Take the pH measurements
dance with the specifications covering the material or product
electrometrically at 25°C (77°F) using a glass electrode with
beingtestedorasmutuallyagreeduponbetweenthepurchaser
a saturated potassium chloride bridge in accordance with Test
and the seller. Exposure periods of multiples of 24 h are
Method E70.
suggested.
NOTE 7—The freshly prepared salt solution may be filtered or decanted
7.4 Cleaning of Tested Specimens—Unless otherwise speci-
before it is placed in the reservoir, or the end of the tube leading from the
solutiontotheatomizermaybecoveredwithadoublelayerofcheesecloth fiedinthespecificationscoveringthematerialorproductbeing
or suitable nonmetallic filter cloth to prevent plugging of the nozzle.
tested, at the end of the test, specimens may be gently washed
or dipped in clean running water no warmer than 38°C
7. Procedure
(100°F) to remove salt deposits from their surface, and then
7.1 Position of Specimens During Test:
immediatelydried.Drywithastreamofclean,compressedair.
7.1.1 Unless otherwise specified, support or suspend the
NOTE 9—Drying with compressed air may not be desirable for
specimens with the surface of interest at an angle between 6
aluminum specimens to be tested for exfoliation corrosion resistance.
and 45° from the vertical. It is recommended that the orienta-
tion of specimens in the cabinet be consistent to minimize
8. Evaluation of Results
variability. Note that test severity increases as angle from the
vertical increases.
8.1 Make a careful and immediate examination for the
extentofcorrosionofthedrytestspecimensorforotherfailure
as required by the specifications covering the material or
“Thermodynamic Properties of the NaCl + H2O system II. Thermodynamic
product being tested or by agreement between the purchaser
Properties of NaCl(aq), NaCl.2H2O(cr), and Phase Equilibria,” Journal of Physics
and Chemistry Reference Data, Vol 21, No. 4, 1992. and the seller.
G85−19
TABLE 2 Temperature versus Density Data
Density, g/cm
Temperature, °C (°F)
4 % Salt 5 % Salt 6 % Salt
Concentration Concentration Concentration
20 (68) 1.025758 1.032360 1.038867
21 (69.8) 1.025480 1.032067 1.038560
22 (71.6) 1.025193 1.031766 1.038245
23 (73.4) 1.024899 1.031458 1.037924
24 (75.2) 1.024596 1.031142 1.037596
25 (77) 1.024286 1.030819 1.037261
26 (78.8) 1.023969 1.030489 1.036919
27 (80.6) 1.023643 1.030152 1.036570
28 (82.4) 1.023311 1.029808 1.036215
29 (84.2) 1.022971 1.029457 1.035853
30 (86) 1.022624 1.029099 1.035485
31 (87.8) 1.022270 1.028735 1.035110
32 (89.6) 1.021910 1.028364 1.034729
33 (91.4) 1.021542 1.027986 1.034343
34 (93.2) 1.021168 1.027602 1.033950
35 (95) 1.020787 1.027212 1.033551
36 (96.8) 1.020399 1.026816 1.033146
37 (98.6) 1.020006 1.026413 1.032735
38 (100.4) 1.019605 1.026005 1.032319
39 (102.2) 1.019199 1.025590 1.031897
40 (104) 1.018786 1.025170 1.031469
9. Report fog-collecting devices for concentration or specific gravity at
23°C 6 3°C (73°F 6 5°F) of solution collected (see Note
9.1 Record the following information, unless otherwise
11) and pH of collected solution. Sample to be measured may
prescribed in the specifications covering the material or prod-
be a composite sample from multiple fog-collecting devices
uct being tested:
(within one test chamber), if necessary to obtain sufficient
9.1.1 Type of salt and water used in preparing the salt
solution volume for measurement.All records of data obtained
solution,
for volume of salt solution collected in millilitres per hour per
9.1.2 All readings of temperature within the exposure zone
each 80 cm fog collecting device. (See 4.3.2.)
of the chamber,
9.1.3 Weekly or daily records, see Note 10, (depending on
NOTE 10—Except on Saturday, Sundays, and holidays, when the test is
notinterruptedforexposing,rearranging,orremovingtestspecimensorto
which test annex is being performed) of data obtained from
check and replenish the solution in the reservoir(s).
eachfog-collectingdeviceforvolumeofsaltsolutioncollected
in millilitres per hour of operation per 80 cm of horizontal 9.1.7 Type of specimen and its dimensions, or number or
collection area. description of part,
9.1.4 Concentration or specific gravity of collected solution 9.1.8 Method of cleaning specimens before and after
and the temperature of that solution when measured. Follow testing,
Table2forsaltconcentrationanddensityversustemperatureto 9.1.9 Method of supporting or suspending article in the salt
determine that the sample measured is within specification. spray chamber,
Sample to be measured may be a composite sample from 9.1.10 Description of protection used as required in 5.2.4,
multiple fog-collecting devices within a single cabinet, if 9.1.11 Exposure period,
necessary, to obtain sufficient solution volume for measure- 9.1.12 Interruptions in test, cause and length of time, and
ment. 9.1.13 Results of all inspections.
9.1.5 pH of collected solution. Sample to be measured may
NOTE 11—It is also advisable to record the concentration or specific
be a composite sample from multiple fog collecting devices
gravity of any atomized salt solution that has not made contact with the
within a single cabinet, if necessary, to obtain sufficient
test specimen and that was returned to the reservoir.
solution volume for measurement.
10. Keywords
9.1.6 Weekly or daily records, see Note 10, (depending on
which test annex is being performed) of data obtained from 10.1 acidic salt spray; corrosion; salt spray
G85−19
...

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: G85 − 11 G85 − 19
Standard Practice for
Modified Salt Spray (Fog) Testing
This standard is issued under the fixed designation G85; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
1.1 This practice covers and sets forth conditions for five modifications in salt spray (fog) testing for specification purposes.
These are in chronological order of their development:
1.1.1 Annex A1,acetic acetic acid-salt spray test, continuous.
1.1.2 Annex A2,cyclic cyclic acidified salt spray test.
1.1.3 Annex A3,seawater seawater acidified test, cyclic (SWAAT).
1.1.4 Annex A4,SO SO salt spray test, cyclic.
1.1.5 Annex A5,dilute dilute electrolyte cyclic fog dry test.
1.2 This practice does not prescribe the type of modification, test specimen or exposure periods to be used for a specific product,
nor the interpretation to be given to the results.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this The values
given in parentheses after SI units are provided for information only and are not considered standard.
1.3.1 Exception—Fahrenheit temperature values are given for information only throughout this practice.
1.4 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 consult and establish appropriate safety safety, health, and healthenvironmental practices and
determine the applicability of regulatory limitations prior to use.
1.5 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:
B117 Practice for Operating Salt Spray (Fog) Apparatus
D609 Practice for Preparation of Cold-Rolled Steel Panels for Testing Paint, Varnish, Conversion Coatings, and Related Coating
Products
D1141 Practice for the Preparation of Substitute Ocean Water
D1193 Specification for Reagent Water
D1654 Test Method for Evaluation of Painted or Coated Specimens Subjected to Corrosive Environments
E70 Test Method for pH of Aqueous Solutions With the Glass Electrode
3. Significance and Use
3.1 This practice is applicable to ferrous and nonferrous metals; also organic and inorganic coatings. The variations described
herein are useful when a different or more corrosive environment than the salt fog described in Practice B117 is desired.
4. Apparatus
4.1 Cabinet:
This practice is under the jurisdiction of ASTM Committee G01 on Corrosion of Metals and is the direct responsibility of Subcommittee G01.05 on Laboratory Corrosion
Tests.
Current edition approved May 1, 2011Nov. 1, 2019. Published August 2011December 2019. Originally approved in 1985. Last previous edition approved in 20092011
as G85–09.–11. DOI: 10.1520/G0085-11.10.1520/G0085–19.
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’sstandard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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4.1.1 The apparatus required for salt spray (fog) testing consists of a fog chamber, a salt solution reservoir, a supply of suitably
conditioned compressed air, one or more atomizing nozzles, specimen supports, provision for heating the chamber, and necessary
means of control. The size and detailed construction of the cabinet are optional, provided the conditions obtained meet the
requirements of this practice. The material of construction shall be such that it will not affect the corrosiveness of the fog. Suitable
apparatus that may be used to obtain these conditions is described in Appendix X1 of Practice B117 with necessary modifications
described in each annex of this practice.
4.1.2 Design the cabinet so that drops of solution that accumulate on the ceiling or cover of the chamber do not fall on the
specimens being tested. Do not return drops of solution that fall from the specimens to the solution reservoir for respraying.
4.1.3 Equip the cabinet with one or more timing devices to provide for intermittent spraying or periodic introduction of a gas,
or both.
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4.2 Air Supply:
4.2.1 Make sure the compressed air supply to the nozzle or nozzles for atomizing the salt solution is free of oil and dirt and
maintain the air supply between 69 and 172 kPa (10 and 25 psi).
NOTE 1—The air supply may be freed of oil and dirt by passing it through a water scrubber or at least 610 mm (2 ft) of suitable cleaning material such
as asbestos, sheep’s wool, or activated alumina.
4.2.2 Temperature in the saturator tower (bubble tower) varies depending on the test method used.
4.3 Conditions in Salt-Spray Chamber:
4.3.1 Temperature—The temperature in the exposure zone varies with the test method used. For recommended exposure zone
temperatures for the various methods, see the annexes in this practice. Each set point and its tolerance represents an operational
control point for equilibrium conditions at a single location in the cabinet which may not necessarily represent the uniformity of
conditions throughout the cabinet. Record the temperature within the exposure zone of the closed cabinet at least twice a day at
least 7 h apart (except on weekends and holidays, when the salt spray test is not interrupted for exposing, rearranging, or removing
test specimens or to check and replenish the solution in the reservoir).
NOTE 2—Suitable methods to record the temperature are a continuous recording device or a thermometer which can be read from outside the closed
cabinet. Obtain the recorded temperature with the salt spray chamber closed to avoid a false low reading because of wet-bulb effect when the chamber
is open.
4.3.2 Atomization and Quantity of Fog—Place at least two clean fog collectors within the exposure zone so that no drops of
solution from the test specimens or any other source can be collected. Position the collectors in the proximity of the test specimens,
one nearest to any nozzle and the other farthest from all nozzles. Make sure that for each 80 cm of horizontal-collecting area fog
accumulates in each collector from 1.0 to 2.0 mL of solution per hour based on an average run of at least 16 h continuous spray.
NOTE 3—Suitable collecting devices are glass funnels with the stems inserted through stoppers into graduated cylinders or crystallizing dishes. Funnels
and dishes with a diameter of 100 mm have an area of about 80 cm .
4.3.3 Direct or baffle the nozzle or nozzles so that none of the spray can impinge directly on the test specimens.
5. Test Specimens
5.1 Define the type and number of test specimens to be used, as well as the criteria for the evaluation of the test results in the
specifications covering the material or product being tested or upon mutual agreement between the purchaser and the seller.
5.2 Preparation of Test Specimens:
5.2.1 Clean metallic and metallic-coated specimens. The cleaning method is optional depending on the nature of the surface and
the contaminants; however, when using a cleaning method do not include in the contents abrasives other than a paste of pure
magnesium oxide nor of solvents which may form corrosive or inhibitive films. The use of nitric acid solution for the chemical
cleaning, or passivation, of stainless steel specimens is permissible when agreed upon between the purchaser and the seller. Take
care that specimens are not recontaminated after cleaning by excessive or careless handling.
5.2.2 Prepare specimens for evaluation of paints and other organic coatings in accordance with applicable specification(s) for
the material(s) being tested, or as agreed upon between the purchaser and supplier. Otherwise, make sure the test specimens consist
of steel meeting the requirements of Practice D609; clean and prepare the specimens for coating in accordance with applicable
procedure of Practice D609.
5.2.3 Whenever it is desired to determine the development of corrosion from an abraded area in the paint or organic coating,
make a scratch or scribed line through the coating with a sharp instrument so that the underlying metal is exposed before testing.
Use the conditions of making the scratch as defined in Test Method D1654, unless otherwise agreed upon between the purchaser
and seller.
5.2.4 Protect the cut edges of plated, coated, or duplex materials and areas that contain identification marks or that are in contact
with the racks or supports with a suitable coating that is stable under the conditions of the test, such as ceresin wax, unless
otherwise specified.
NOTE 4—Should it be desirable to cut test specimens from parts or from preplated, painted, or otherwise coated-steel sheet, protect the cut edges by
coating them with paint, wax, tape, or other effective media so that the development of preferential attack or a galvanic effect between such edges and
the adjacent plated or otherwise coated-metal surfaces, is prevented.
6. Salt Solutions
6.1 Make the salt solutions by using either synthetic sea salt in accordance with Practice D1141 or sodium chloride in
accordance with Practice B117, unless otherwise specified in the appropriate annex. Make-up water shall be distilled or deionized
water conforming to Type IV water in Specification D1193 (except that for this practice, limits for chlorides and sodium may be
ignored).
6.2 Synthetic Sea Salt Solution (see Annex A3)—Make the salt solution so that it consists of 42 g of synthetic sea salt in
accordance with Practice D1141 per litre of solution (see Note 5).
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6.3 Sodium Chloride Solution (Except Annex A3 and Annex A5): Prepare the salt solution by dissolving 5 6 1 parts by weight
of sodium chloride in 95 parts of water conforming to Type IV water in Specification D1193 (except that for this practice, limits
for chlorides and sodium may be ignored) containing not more than 200 ppm of total solids (see Note 5). Halides (Bromide,
Fluoride, and Iodide) other than Chloride shall constitute less than 0.1 % by mass of the salt content. Copper content shall be less
than 0.3 ppm by mass. Sodium chloride that has had anti-caking agents added shall not be used because such agents may act as
corrosion inhibitors (see Note 6). See Table 1 for a listing of these impurity restrictions. Upon agreement between the purchaser
and the seller, analysis may be required and limits established for elements or compounds not specified in the chemical composition
given above.
TABLE 1 Maximum Allowable Limits for Impurity Levels in
Sodium Chloride
Impurity Description Allowable Amount
Total Impurities #0.3%
Halides (Bromide, Fluoride and Iodide) < 0.1 %
excluding Chloride
Halides (Bromide, Fluoride and Iodide) <0.1 %
excluding Chloride
Copper < 0.3 ppm
Copper <0.3 ppm
Anti-caking Agents None Added
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TABLE 2 Temperature versus Density Data
Density, g/cm
Temperature, °C (°F)
4%4 % Salt 5%5 % Salt 6%6 % Salt
Concentration Concentration Concentration
20 (68) 1.025758 1.032360 1.038867
21 (69.8) 1.025480 1.032067 1.038560
22 (71.6) 1.025193 1.031766 1.038245
23 (73.4) 1.024899 1.031458 1.037924
24 (75.2) 1.024596 1.031142 1.037596
25 (77) 1.024286 1.030819 1.037261
26 (78.8) 1.023969 1.030489 1.036919
27 (80.6) 1.023643 1.030152 1.036570
28 (82.4) 1.023311 1.029808 1.036215
29 (84.2) 1.022971 1.029457 1.035853
30 (86) 1.022624 1.029099 1.035485
31 (87.8) 1.022270 1.028735 1.035110
32 (89.6) 1.021910 1.028364 1.034729
33 (91.4) 1.021542 1.027986 1.034343
34 (93.2) 1.021168 1.027602 1.033950
35 (95) 1.020787 1.027212 1.033551
36 (96.8) 1.020399 1.026816 1.033146
37 (98.6) 1.020006 1.026413 1.032735
38 (100.4) 1.019605 1.026005 1.032319
39 (102.2) 1.019199 1.025590 1.031897
40 (104) 1.018786 1.025170 1.031469
NOTE 5—The specific gravity of salt solution will change with temperature. Table 2 shows salt concentration and density versus temperature and can
be used to determine if the sample measured is within specification. The sample to be measured may be a composite sample from multiple fog-collecting
devices within a single cabinet, if necessary, to obtain sufficient solution volume for measurement.
Table 2 shows the salt concentration and salt density of 4%, 5%,4 %, 5 %, and 6%6 % salt solution between 20 and 40°C.40 °C. A measurement that
falls within the range between 4 and 6%6 % is acceptable.
It is important to understand the equipment being used to measure specific gravity. One common practice for specific gravity measurement is the use
of a hydrometer. If used, careful attention to the hydrometer type is important as most are manufactured and calibrated for measurements at
15.6°C.15.6 °C. Since salt density is temperature dependent an offset will be necessary to make an accurate measurement at other temperatures. Contact
the hydrometer manufacturer to find the proper offset for the hydrometer being used.
NOTE 6—A measurable limit for anti-caking agents is not being defined as a result of how salt is manufactured. During salt manufacturing, it is common
practice to create salt slurry from the raw salt mined. A crystallization process then captures the pure salt from this slurry. Some naturally occurring
anti-caking agents can be formed in this process and are not removed from the resultant product. Avoid salt products where extra anti-caking agents are
added. Additionally, when doing an elemental analysis of salt there can be trace elements present that either stand alone or are part of an anti-caking agent.
It is not economically feasible to know where such elements came from due to the long list of possible anti-caking agents that would have to be tested.
Therefore a salt product that meets the impurity, halide, and copper limits with no anti-caking agents added is acceptable. The salt supplier can provide
an analysis of the salt with a statement indicating that anti-caking agents were not added to the product.
6.4 The pH of the salt solutions will vary depending on the test method used. Before the solution is atomized, free it of
suspended solids (see Note 7). Take the pH measurements electrometrically at 25°C (77°F)25 °C (77 °F) using a glass electrode
with a saturated potassium chloride bridge in accordance with Test Method E70.
NOTE 7—The freshly prepared salt solution may be filtered or decanted before it is placed in the reservoir, or the end of the tube leading from the
solution to the atomizer may be covered with a double layer of cheesecloth or suitable nonmetallic filter cloth to prevent plugging of the nozzle.
7. Procedure
7.1 Position of Specimens During Test:
7.1.1 Unless otherwise specified, support or suspend the specimens with the surface of interest at an angle between 6 and 45°
from the vertical, and preferably parallel to the principal direction of horizontal flow of fog through the chamber, based upon the
dominant surface being tested. vertical. It is recommended that the orientation of specimens in the cabinet be consistent to
minimize variability. Note that test severity increases as angle from the vertical increases.
7.1.2 Do not allow contact of the specimens between each other, between any metallic material, or between any material capable
of acting as a wick.
7.1.3 Place each specimen so as to permit free settling of fog on all specimens. A minimum spacing between specimens of 30
mm is recommended.
7.1.4 Do not permit the salt solution from one specimen to drip on any other specimen.
7.1.5 It is recommended that placement of replicate specimens be randomized to avoid possible bias caused by difference in
spray patterns. Individual specimens may also be rotated daily for the same reason.
“Thermodynamic Properties of the NaCl + H2O system II. Thermodynamic Properties of NaCl(aq), NaCl.2H2O(cr), and Phase Equilibria,” Journal of Physics and
Chemistry Reference Data, Vol 21, No. 4, 1992.
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7.1.6 Suitable materials for the construction or coating of racks and supports are glass, rubber, plastic, or suitably coated wood.
Do not use bare metal. Support specimens preferably from the bottom or the side. Slotted wooden, laminated plastic, or inert plastic
strips are suitable for the support of flat panels. Suspension from glass hooks or waxed string may be used as long as the specified
position of the specimens is obtained, and, if necessary, by means of secondary support at the bottom of the specimens.
7.2 Continuity of Test—Unless otherwise specified in the specifications covering the material or product being tested, the test
shall be continuous for the duration of the entire test period. Continuous operation implies that the chamber be closed except for
the short daily interruptions necessary to inspect, rearrange, or remove test specimens, to check and replenish the solution in the
reservoir, and to make necessary recordings as described in 4.3.1, 4.3.2, and Section 9. (See Note 8.)
NOTE 8—Operations should be so scheduled that the cumulative maximum time for these interruptions are held to 60 min or less per day. It is
recommended to have only one interruption per day if possible. If interruption time is longer that 60 min, it should be noted in the test report.
7.3 Period of Test—Designate the period of test in accordance with the specifications covering the material or product being
tested or as mutually agreed upon between the purchaser and the seller. Exposure periods of multiples of 24 h are suggested.
7.4 Cleaning of Tested Specimens—Unless otherwise specified in the specifications covering the material or product being
tested, at the end of the test, specimens may be gently washed or dipped in clean running water no warmer than 38°C (100°F)38 °C
(100 °F) to remove salt deposits from their surface, and then immediately dried. Dry with a stream of clean, compressed air.
NOTE 9—Drying with compressed air may not be desirable for aluminum specimens to be tested for exfoliation corrosion resistance.
8. Evaluation of Results
8.1 Make a careful and immediate examination for the extent of corrosion of the dry test specimens or for other failure as
required by the specifications covering the material or product being tested or by agreement between the purchaser and the seller.
9. Report
9.1 Record the following information, unless otherwise prescribed in the specifications covering the material or product being
tested:
9.1.1 Type of salt and water used in preparing the salt solution,
9.1.2 All readings of temperature within the exposure zone of the chamber,
9.1.3 Weekly or daily records, see Note 10, (depending on which test annex is being performed) of data obtained from each
fog-collecting device for volume of salt solution collected in millilitres per hour of operation per 80 cm of horizontal collection
area.
9.1.4 Concentration or specific gravity of collected solution and the temperature of that solution when measured. Follow Table
2 for salt concentration and density versus temperature to determine that the sample measured is within specification. Sample to
be measured may be a composite sample from multiple fog-collecting devices within a single cabinet, if necessary, to obtain
sufficient solution volume for measurement.
9.1.5 pH of collected solution. Sample to be measured may be a composite sample from multiple fog collecting devices within
a single cabinet, if necessary, to obtain sufficient solution volume for measurement.
9.1.6 Weekly or daily records, see Note 10, (depending on which test annex is being performed) of data obtained from
fog-collecting devices for concentration or specific gravity at 2323 °C 6 3°C (733 °C (73 °F 6 5°F)5 °F) of solution collected (see
Note 11) and pH of collected solution. Sample to be measured may be a composite sample from multiple fog-collecting devices
(within one test chamber), if necessary to obtain sufficient solution volume for measurement. All records of data obtained for
volume of salt solution collected in millilitres per hour per each 80 cm fog collecting device. (See 4.3.2.)
NOTE 10—Except on Saturday, Sundays, and holidays, when the test is not interrupted for exposing, rearranging, or removing test specimens or to check
and replenish the solution in the reservoir(s).
9.1.7 Type of specimen and its dimensions, or number or description of part,
9.1.8 Method of cleaning specimens before and after testing,
9.1.9 Method of supporting or suspending article in the salt spray chamber,
9.1.10 Description of protection used as required in 5.2.4,
9.1.11 Exposure period,
9.1.12 Interruptions in test, cause and length of time, and
9.1.13 Results of all inspections.
NOTE 11—It is also advisable to record the concentration or specific gravity of any atomized salt solution that has not made contact with the test
specimen and that was returned to the reservoir.
10. Keywords
10.1 acidic salt spray; corrosion; salt spray
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ANNEXES
(Mandatory Information)
A1. ACETIC ACID-SALT SPRAY (FOG) TESTING
A1.1 Salt Solution
A1.1.1 A sodium chloride solution made in accordance with 6.3.
A1.1.2 Adjust the pH of this solution measured in accordance with Test Method E70 to range from 3.1 to 3.3 by the addition of
acetic acid.
NOTE A1.1—The initial solution may be adjusted to pH of 3.0 to 3.1 with the expectation that the pH of the collected fog will be within the specified
limits. Base the adjustment of the initial pH for make-up solution upon the requirements to maintain the required pH of the collected samples. If less than
0.1 or more than 0.3 % of the glacial acetic acid is required to attain the specified pH, the purity of the water or salt, or both may not be satisfactory.
A1.2 Conditions in Saturator Tower
A1.2.1 Make sure the temperature i
...