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ASTM G85 Standard Practice for Modified Salt Spray (Fog) Testing

ASTM G85, along with ASTM B117, forms the foundation for ensuring the reliability and corrosion resistance of materials and products. Salt spray testing allows manufacturers to identify potential weaknesses and make improvements to their products. By adhering to these internationally recognized standards, companies can establish trust with their customers and provide durable products that stand the test of time. Incorporating corrosion testing methods, such as salt spray testing, into the manufacturing process is essential for guaranteeing product performance and quality across various industries.

ASTM G85 defines the procedures for conducting salt spray tests, also referred to as salt fog testing. The salt spray test subjects test samples to a controlled saline environment, whereby a salt fog is created. The samples are evaluated for their ability to withstand corrosion, and the results are analyzed to determine their performance and durability in real-world applications.

When it comes to evaluating the corrosion resistance of materials and products, the ASTM G85 standard plays a crucial role. This widely recognized standard outlines the guidelines and specifications for Modified Salt Spray (Fog) Testing. In this article, we will delve into the details of this testing method, including its relevance, procedures, and significance in corrosion testing. Let’s explore the ins and outs of ASTM G85 and its implications for various industries.

ASTM G85 - 11 《Standard Practice for Modified Salt Spray (Fog) Testing》
Type and Description WEW-YW-90D WEW-YW-120D WEW-YW-160D
Inner Dimension(mm) 900*600*500 1200*800*500 1600*1000*600
Outer Dimension(mm) 1410*880*1280 1700*1150*1200 2300*1250*1450
Test Room Size (Liters) 270 Liters 500 Liters 1000 Liters
Power Supply AC 220V, 50Hz AC 220V, 50Hz AC 380V, 50Hz
Power Current 1Phase, 2.0 kW 1Phase, 2.9 kW 3Phase, 5.0 kW
Lid Opening Method Manual Opening Manual Opening Air-Operated
Brine Tank Volume 25 Literes 30 Literes 40 Literes
Test Room Temp Range Ambient Temperature +5℃ – +30℃, Ventilation is recommended, if the temperature exceeds +30℃, it is recommended to adjust the room temperature by suitable means. Ambient humidity should be controlled below 80%RH.
Test Room Temp Range RT+10℃ – +55℃ RT+10℃ – +55℃ RT+10℃ – +55℃
Saturated Barrel  RT+10℃ – +70℃ (Purpose: Heating and filtering of compressed air to reduce nozzle crystallisation.)
Temp Performance Temperature Uniformity: ≤2℃,  Temperature Fluctuation: ≤ ±0.5°C Temperature Uniformity: ≤2℃, 
Salt Mist Settling Rate 1~2 ml/80 cm2/h (Take 16 Hours To Test The Average Value) 1~2 ml/80 cm2/h
Spray Method Continuous, Intermittent,  Programmable Tests Continuous, Intermittent, 
Testing Type NSS, AASS,CASS NSS, AASS,CASS NSS, AASS,CASS
Safety Devices Over-Temperature Alarm (Mechanical Over-Temperature Protection + Electronic Over-Temperature Protection Double Over-Temperature Protection)
Air Requirements Two-Stage Pressure Regulation. Inlet Pressure Above 0.4Mp. Spray Pressure 0.07~0.17mp (Adjustable)
Sample Holder Special Samples Support Customisation. Special Samples Support Customisation. Load Capacity According To Actual Situation
Standard Configuration 1 Set Of V-Type/O-Type Shelves, 2 Bottles Of Test Drug Sodium Chloride (500g/Bottle), 1 Plastic Anti-Rust Bucket (5l Capacity), 1 Nozzle

The ASTM G85 standard holds significant value for a wide range of materials, including ferrous and nonferrous metals, as well as organic and inorganic coatings. It provides a framework for assessing corrosion resistance in diverse environments beyond the scope of the salt fog conditions outlined in Practice B117. By incorporating variations outlined in this standard, researchers and industry professionals can tailor their corrosion testing to simulate specific real-world conditions, enabling a more comprehensive understanding of material performance in varying environments.

7.1.1 Unless otherwise specified,support or suspend thespecimens between 6 and 45° from the vertical, and preferablyparallel to the principal direction of horizontal flow of fogthrough the chamber,based upon the dominant surface beingtested. Note that test severity increases as angle from thevertical increases. 7.1 Position of Specimens During Test: Test Procedure
7.1.2 Do not allow contact of the specimens between eachother,between any metallic material, or between any materialcapable of acting as a wick.
7.1.3 Place each specimen so as to permit free settling of fogon all specimens.A minimum spacing between specimens of30 mm is recommended.
7.1.4 Do not permit the salt solution from one specimen todrip on any other specimen.
7.1.5 It is recommended that placement of replicate speci-mens be randomized to avoid possible bias caused by differ-ence in spray patterns. Individual specimens may also berotated daily for the same reason.
7.1.6 Suitable materials for the construction or coating ofracks and supports are glass, rubber, plastic, or suitably coatedwood. Do not use bare metal. Support specimens preferablyfrom 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 aslong as the specified position of the specimens is obtained, and,if necessary, by means of secondary support at the bottom ofthe specimens.
Unless otherwise specified in thespecifications covering the material or product being tested, the test shall be continuous for the duration of the entire testperiod. Continuous operation implies that the chamber beclosed except for the short daily interruptions necessary toinspect,rearrange,or remove test specimens,to check andreplenish the solution in the reservoir, and to make necessaryrecordings as described in 4.3.1,4.3.2,and Section 9. (SeeNote 8.) 7.2 Continuity of Test: 
Note 8: Operations should be so scheduled that the cumulativemaximum 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. Ifinterruption time is longer that 60 min, it should be noted in the test report.
Period of Test-Designate the period of test in accor-dance with the specifications covering the material or productbeing tested or as mutually agreed upon between the purchaserand the seller. Exposure periods of multiples of 24 h aresuggested. 7.3 Period of Test-Designate 
Unless otherwise speci-fied in the specifications covering the material or product beingtested, at the end of the test,specimens may be gently washedor dipped in clean running water no warmer than 38℃ (100°F)to remove salt deposits from their surface, and then immedi-ately dried. Dry with a stream of clean,compressed air. 7.4 Cleaning of Tested Specimens: 
NoTE 9: Drying with compressed air may not be desirable foraluminum specimens to be tested for exfoliation corrosion resistance.
salt spray testing
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 thespecifications covering the material or product being tested orupon mutual agreement between the purchaser and the seller. 5.1 Define the Type and Qty Test Specimens
5.2.1 Clean metallic and metallic-coated specimens. Thecleaning method is optional depending on the nature of thesurface and the contaminants; however, when using a cleaningmethod do not include in the contents abrasives other than apaste of pure magnesium oxide nor of solvents which mayform corrosive or inhibitive films. The use of nitric acidsolution for the chemical cleaning, or passivation,of stainlesssteel specimens is permissible when agreed upon between thepurchaser and the seller. Take care that specimens are notrecontaminated after cleaning by excessive or careless han-dling. 5.2 Preparation of Test Specimens:
5.2.2 Prepare specimens for evaluation of paints and otherorganic coatings in accordance with applicable specification(s)for the material(s) being tested, or as agreed upon between thepurchaser and supplier. Otherwise,make sure the test speci-mens consist of steel meeting the requirements of Practice D609; clean and prepare the specimens for coating in accor-dance with applicable procedure of Practice D609.
5.2.3 Whenever it is desired to determine the developmentof corrosion from an abraded area in the paint or organiccoating, make a scratch or scribed line through the coating witha sharp instrument so that the underlying metal is exposedbefore testing. Use the conditions of making the scratch asdefined in Test Method D1654, unless otherwise agreed uponbetween the purchaser and seller.
5.2.4 Protect the cut edges of plated,coated,or duplexmaterials and areas that contain identification marks or that arein contact with the racks or supports with a suitable coating thatis 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 frompreplated,painted, or otherwise coated-steel sheet,protect the cut edgesby coating them with paint, wax, tape, or other effective media so that thedevelopment of preferential attack or a galvanic effect between such edgesand the adjacent plated or otherwise coated-metal surfaces, is prevented.

The core of corrosion testing methods, ASTM G85, provides guidance on the appropriate procedures for subjecting materials to a corrosive salt spray environment. This standard ensures the consistent and accurate evaluation of material performance in corrosive environments. By simulating harsh environmental conditions, the test assesses the effectiveness of protective coatings and identifies potential vulnerabilities.

ASTM G85 and its salt spray testing method play a vital role in various industries, including automotive, aerospace, electronics, and construction. Manufacturers rely on this standard to ensure that their products’ protective coatings are effective and can withstand harsh environments, such as coastal areas or industrial settings.

ASTM B117 is a related standard that specifically focuses on the salt spray test method. While ASTM G85 covers multiple test methods, ASTM B117 provides detailed procedures for neutral salt spray testing. It is important to understand the differences and specific applications of each standard to choose the appropriate method for specific product testing needs. To carry out the salt spray test, a salt mist test chamber is utilized.

This specialized chamber creates a controlled environment where precise conditions can be maintained. The test specimens are exposed to the salt fog for a specified duration, typically ranging from hours to hundreds or more hours, depending on the requirements and objectives of the test. The corrosion products produced during exposure are examined to assess the test specimen’s performance.

salt spray fog apparatus
4.1.1 The apparatus required for salt spray (fog) testingconsists of a fog chamber, a salt solution reservoir, a supply ofsuitably conditioned compressed air,one or more atomizingnozzles, specimen supports, provision for heating the chamber,and necessary means of control. The size and detailed con-struction of the cabinet are optional, provided the conditionsobtained meet the requirements of this practice. The material ofconstruction shall be such that it will not affect the corrosive-ness of the fog. Suitable apparatus that may be used to obtainthese conditions is described in Appendix X1 of Practice B117with necessary modifications described in each annex of thispractice. 4.1 Cabinet: Test Apparatus
4.1.2 Design the cabinet so that drops of solution thataccumulate on the ceiling or cover of the chamber do not fall1on 5Bqacimens being tested. Do not return drops of solutionthat fall from the specimens to the solution reservoir forrespraying.
4.1.3 Equip the cabinet with one or more timing devices toprovide for intermittent spraying or periodic introduction of agas, or both.
4.2.1 Make sure the compressed air supply to the nozzle ornozzles for atomizing the salt solution is free of oil and dirt andmaintain the air supply between 69 and 172 kPa (10 and 25psi). 4.2 Air Supply:
4.2.2Temperature in the saturator tower (bubble tower)varies depending on the test method used.
4.3.1 Temperature: The temperature in the exposure zonevaries with the test method used. For recommended exposurezone temperatures for the various methods, see the annexes inthis practice. Each set point and its tolerance represents anoperational control point for equilibrium conditions at a singlelocation in the cabinet which may not necessarily represent theuniformity of conditions throughout the cabinet. Record thetemperature within the exposure zone of the closed cabinet atleast twice a day at least 7 h apart (except on weekends andholidays,when the salt spray test is not interrupted forexposing, rearranging, or removing test specimens or to checkand replenish the solution in the reservoir). 4.3 Conditions in Salt-Spray Chamber:
Note 2: : Suitable methods to record the temperature are a continuousrecording device or a thermometer which can be read from outside theclosed cabinet. Obtain the recorded temperature with the salt spraychamber closed to avoid a false low reading because of wet-bulb effectwhen the chamber is open.
4.3.2 Atomization and Quantity of Fog: Place at least twoclean fog collectors within the exposure zone so that no dropsof solution from the test specimens or any other source can becollected. Position the collectors in the proximity of the test specimens, one nearest to any nozzle and the other farthestfrom all nozzles.
Make sure that for each 80 cm2 of horizontal-collecting area fog accumulates in each collector from 1.0 to2.0 mL of solution per hour based on an average run of at least16 h continuous spray.
Note 3: : Suitable collecting devices are glass funnels with the stemsinserted through stoppers into graduated cylinders or crystallizing dishes.Funnels and dishes with a diameter of 100 mm have an area of about 80cm2.
4.3.3 Direct or baffle the nozzle or nozzles so that none ofthe spray can impinge directly on the test specimens.
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