A Complete Guide to ASTM G85 Standard: Core Guidelines and Application Analysis of Modified Salt Spray Testing
In the field of material corrosion testing, the ASTM G85 standard is one of the internationally recognized core specifications. Its full name is “Standard Practice for Modified Salt Spray (Fog) Testing”, formulated and released by ASTM International, and approved for use by agencies under the U.S. Department of Defense. It is widely used in the corrosion resistance evaluation of metal materials, surface coatings and other products, and serves as an important technical basis for product quality verification, third-party testing and international trade compliance. Compared with the traditional salt spray testing standard ASTM B117, ASTM G85 focuses more on simulating complex and real corrosion environments, and provides more accurate technical support for corrosion resistance testing of materials in different scenarios through a variety of modified test methods.
我. Development Background and Core Positioning of ASTM G85 Standard
The ASTM G85 standard was first released in 1985 and has been revised and improved many times. The latest version is ASTM G85-19 released in 2019, where “19” in the code represents its revision year. Its development process profoundly reflects the evolution trend of corrosion testing technology from simple accelerated corrosion to complex environment simulation — the traditional ASTM B117 salt spray test mainly relies on a constant salt spray environment, which is difficult to simulate complex working conditions such as temperature fluctuations, dry-wet alternation, and coexistence of harmful gases in practical applications. The launch of ASTM G85 just makes up for this shortcoming and becomes an important supplement to the ASTM B117 standard.
In terms of standard positioning, ASTM G85 is a U.S. industry general standard. Although it is not legally mandatory, it is widely adopted by local manufacturing enterprises, testing institutions and purchasers due to its accurate coverage of the mainstream corrosion environment simulation needs of the North American market. Especially for products exported to the United States and Canada, passing the test according to this standard is a key prerequisite for proving their corrosion resistance and obtaining market access.
The core scope of application of this standard includes ferrous metals, 有色金属, as well as organic and inorganic coatings. It explicitly excludes non-metallic materials (such as plastics and rubber) and natural environment exposure tests. Its core purpose is to quickly evaluate the corrosion resistance of materials and surface protective layers in practical use through artificially simulated accelerated corrosion environments, and provide scientific basis for product design, material selection and quality control.
二. Core Test Methods of ASTM G85 Standard (Classification by Five Appendices)
ASTM G85 is not a single test method, but includes five modified salt spray test methods, presented in the form of appendices in the order of development. Each method is aimed at specific corrosion mechanisms and environmental conditions, and can be flexibly selected according to testing needs. The differences among these five methods are mainly reflected in test environment, solution ratio, cycle process and other aspects, and the specific analysis is as follows:
(我) Appendix A1: Continuous Acetic Acid Salt Spray Test
As one of the earliest developed methods, Appendix A1 is mainly aimed at scenarios that need to simulate acidic salt spray environments. By adjusting the pH value of the salt spray solution to the acidic range, it simulates the corrosion effect of industrial atmosphere, coastal acidic environment and other conditions on materials. This method adopts a continuous spray mode, with relatively stable test conditions and simple operation. It is suitable for the preliminary evaluation of corrosion resistance of materials and coatings in acidic environments, and is widely used in routine testing of surface treatment products such as electroplating layers and chemical conversion films.
(二) Appendix A2: Cyclic Acidic Salt Spray Test
Compared with the continuous spray of Appendix A1, Appendix A2 introduces a “spray-drying” cycle mode, which is closer to the characteristics of day and night dry-wet alternation in the natural environment. 测试期间, by periodically switching between the spray stage and the drying stage, it simulates the impact of environmental humidity fluctuations on material corrosion, and can more truly reflect the corrosion resistance performance of materials and coatings in practical use. It is suitable for products that are in dry-wet alternating environments for a long time, such as auto parts and outdoor hardware.
(III) Appendix A3: Cyclic Acidified Seawater Test (SWAAT)
Appendix A3 mainly simulates the corrosion conditions of marine environment and coastal industrial environment. It uses acidified seawater solution as the spray medium, combined with the cyclic spray-drying process, to focus on evaluating the corrosion resistance of materials and coatings in the dual environment of high salt and acidity. This method has extremely high pertinence to products used in coastal areas (such as marine parts, coastal building hardware, marine equipment), and is one of the commonly used methods for marine engineering material testing.
(IV) Appendix A4: Cyclic SO₂ Salt Spray Test
This method mainly simulates the corrosion environment containing harmful gases such as sulfur dioxide in the industrial atmosphere. By introducing SO₂ gas into the salt spray environment, it simulates the corrosion effect of acid rain and industrial waste gas on materials. It is suitable for evaluating the corrosion resistance of materials and coatings in industrial pollution environments, such as testing of steel structures, boiler components, industrial equipment and other products.
(V) Appendix A5: Dilute Electrolyte Spray and Dry Cycle Test (Prohesion Test)
Appendix A5 is also known as the Prohesion Test (abbreviation of “Protection is Adhesion”), which is the one closest to the natural exposure environment among the five methods. This method uses a diluted electrolyte solution as the spray medium, combined with a complex cycle process of “spray-drying-wetting”, to simulate the corrosion conditions of alternating rain, dew and dryness in the outdoor atmosphere, and has a very high correlation with the results of long-term natural exposure tests.
Compared with other methods, the test conditions of Appendix A5 are relatively mild, but it can more truly reflect the long-term corrosion resistance of materials and coatings. It is especially suitable for the testing of steel surface paints, industrial maintenance coatings and other products, and can effectively show common corrosion defects such as blistering and delamination of coatings, providing important reference for coating formula optimization and construction quality control.
III. Core Test Requirements of ASTM G85 Standard
Regardless of which test method is selected, ASTM G85 puts forward clear requirements for test equipment, solution preparation, test condition control, sample handling and result evaluation to ensure the operability, reproducibility and accuracy of the test. The core requirements are as follows:
(我) Test Equipment Requirements
Test equipment mainly includes spray chamber, salt solution tank, compressed air source, atomizing nozzle, sample holder, heating device and time controller. The material of the equipment shall not affect the corrosion effect of the spray. The equipment described in Appendix A1 of ASTM B117 can be adopted and appropriately improved according to different test methods. The core requirements include:
•The design of the spray chamber shall prevent the droplets condensed on the top from falling on the samples, and the solution dripping from the samples shall not be recycled to the salt solution tank for reuse;
•The compressed air shall be oil-free and free of pollutants, with the pressure controlled at 69kPa~172kPa (10psi~25psi). Oil and impurities can be removed through a water washing tower or washing materials;
•A time controller shall be equipped to realize periodic spray and compressed air input, so as to meet the process requirements of cyclic tests;
•At least two salt spray collectors shall be placed in the exposure area to ensure that during 16 hours of continuous spray, the amount of solution collected per hour by each collector (with a horizontal area of 80cm²) is between 1.0~2.0mL.
(二) Solution Preparation Requirements
Solution preparation shall comply with relevant ASTM standards. The core raw materials include reagent-grade water (in line with ASTM D1193 specification), sodium chloride and other modified reagents (例如醋酸, sulfur dioxide, ETC。). The solution ratio varies with different test methods:
•The conventional salt spray solution mostly adopts 5% sodium chloride aqueous solution, which is consistent with the ASTM B117 standard;
•The acidic salt spray solution (Appendices A1, A2, A3) needs to adjust the pH value to the specified range by adding acetic acid;
•The simulated seawater solution (Appendix A3) shall comply with the ASTM D1141 artificial seawater specification;
•After the solution is prepared, the pH value shall be measured with a glass electrode (in line with ASTM E70 standard) to ensure that it meets the test requirements.
(III) Test Condition Control
The stability of test conditions directly affects the accuracy of test results. The core control indicators include temperature, spray cycle, exposure time, ETC。:
•Temperature control: The temperature of the exposure area varies according to different test methods and needs to be continuously monitored. It shall be recorded at least twice a day (with an interval of not less than 7 小时, except weekends and holidays). The recording shall be carried out when the test chamber is closed to avoid temperature error caused by opening the chamber;
•Spray control: Direct spraying of salt spray on the sample surface is prohibited, which can be achieved by adjusting the nozzle angle; For cyclic tests, the specified spray-drying cycle shall be strictly followed (例如, the Appendix A1 type test commonly uses a cycle mode of 8 hours spray and 16 hours drying);
•Exposure time: The standard does not specify a unified exposure cycle, which shall be determined according to product use, relevant specifications and mutual agreement between the two parties, usually 3~10 cycles or continuous exposure for a certain period of time.
(IV) Sample Handling and Result Evaluation
Sample handling shall comply with relevant standards such as ASTM D609 (Standard Practice for Preparation of Cold-Rolled Steel Panels for Testing Paint, Varnish, Conversion Coatings, and Related Coating Products). Before the test, the sample surface shall be cleaned to remove oil, dust and other impurities to ensure that the surface is free of damage and moisture; The sample holder shall be made of corrosion-resistant materials, and the placement angle shall meet the requirements to avoid affecting the salt spray contact effect.
测试后, the results shall be evaluated in accordance with standards such as ASTM D1654 (Standard Test Method for Evaluation of Painted or Coated Specimens After Exposure to Corrosive Environments). The core evaluation indicators include: the formation of corrosion products on the sample surface, the degree of blistering, cracking and peeling of the coating. 如果需要的话, quantitative evaluation can be carried out by methods such as microscopic observation, corrosion pit depth measurement and weight loss analysis. 最后, a detailed test report shall be formed, clarifying the test conditions, process and result judgment.
IV. Core Differences Between ASTM G85 and ASTM B117
As two commonly used standards in the field of corrosion testing, ASTM G85 and ASTM B117 are often compared. The core differences between them are mainly reflected in three aspects: test design, environment simulation and application scenarios. The specific comparison is as follows:
| Comparison Dimension | ASTM G85 | ASTM B117 |
| Test Design | Including five modified methods, mainly cyclic tests, capable of simulating complex working conditions | Single continuous salt spray test with relatively simple design |
| Environment Simulation | Close to real service environment, capable of simulating complex conditions such as acidity, SO₂ pollution and dry-wet alternation | Only simulating a single salt spray environment, with a large gap from actual working conditions |
| Application Scenarios | High-end products, products exported to North America, requiring accurate evaluation of long-term corrosion resistance | Preliminary testing of conventional products, rapid screening of corrosion resistance |
| Corrosion Characteristics | Simulating real corrosion forms such as cyclic corrosion and cracks, with more referential results | Mainly uniform corrosion, difficult to reflect actual corrosion defects |
V. Practical Application Scenarios of ASTM G85 Standard
With its accurate environment simulation capability and international recognition, the ASTM G85 standard is widely used in many industries, becoming an important support for product quality control and technological research and development. The core application scenarios include:
1.Automotive Industry: Used for corrosion resistance testing of auto parts (such as vehicle body, 机壳, fasteners). Especially for automotive products exported to the North American market, it is necessary to verify their corrosion resistance in rain and snow, industrial pollution, coastal environments and other conditions through ASTM G85 tests to ensure product service life.
2.Aerospace Industry: Used for testing surface coatings and metal materials of aerospace components and equipment, simulating the corrosion effect of complex environments such as high altitude, marine and industrial pollution on equipment, and ensuring the reliability of equipment under extreme conditions.
3.Building Hardware Industry: Used for testing door and window hardware, curtain wall accessories, fasteners and other products, simulating outdoor dry-wet alternation, acid rain, coastal salt spray and other environments, evaluating the weather resistance and corrosion resistance of products, and ensuring the safety and durability of building structures.
4.Electronic and Electrical Industry: Used for testing surface protective layers of electronic components, 连接器, circuit boards and other products, simulating the corrosion impact of humid and salt spray environments on electronic equipment, and avoiding circuit failures caused by corrosion.
5.Coating Industry: Used for testing industrial maintenance coatings, marine coatings, automotive coatings and other products. Especially through the Appendix A5 test, it evaluates the long-term corrosion resistance of coatings in outdoor environments, optimizing coating formulas and construction processes.
VI. Precautions for the Use of ASTM G85 Standard
In the actual application of the ASTM G85 standard for testing, the following points shall be noted to ensure the accuracy and effectiveness of test results:
•Rational Selection of Test Methods: The corresponding appendix test method shall be selected according to the actual service environment, material and protective type of the product to avoid the loss of reference value of test results due to improper selection;
•Equipment Calibration: Test equipment shall be calibrated regularly, including temperature sensors, pressure gauges, salt spray collectors, ETC。, to ensure that equipment parameters meet standard requirements;
•Safe Operation: The test involves corrosive substances such as acidic solutions and SO₂ gas. Operators shall wear protective equipment and formulate reasonable safety protection measures to avoid safety accidents;
•Report Completeness: The test report shall detailedly record test conditions (方法, 温度, cycle, solution ratio), sample information, test process, result evaluation and other contents to ensure the traceability and authority of the report;
•Version Update: Attention shall be paid to the latest revision dynamics of the standard, and the latest version (ASTM G85-19) shall be preferred for testing to ensure that test results meet current market and industry requirements.
VII. 概括
As the core standard for modified salt spray testing, ASTM G85 has become an important specification in the international corrosion testing field after decades of development and improvement. Its five appendix test methods cover a variety of scenarios from simple acidic salt spray to complex cyclic corrosion, which can accurately simulate real service environments and provide scientific and reliable technical basis for the evaluation of corrosion resistance of materials and products.
For manufacturing enterprises, mastering the core requirements and application methods of the ASTM G85 standard can not only improve the level of product quality control, screen better materials and protective processes, but also help products smoothly enter the North American market and enhance market competitiveness. For testing institutions, carrying out testing work in strict accordance with this standard can ensure the accuracy and authority of test results and provide reliable technical services for enterprises.
With the continuous development of corrosion testing technology, the ASTM G85 standard will also be continuously optimized, further improving the authenticity of environment simulation and the accuracy of tests, and providing more powerful support for product research and development and quality improvement in various industries.
Our product GA-2008 Wet And Dry Combined Salt Spray Tester meets this standard.
Wet And Dry Combined Salt Spray Tester
满足标准:
GB/T5170.8, GB/T10587, GJB150.11, GB/T10125, GB/T2423.17, ETC.
DIN50021 DIN50017 DIN50907 ISO 11977 国际标准化组织 9227 ASTM B117
ASTM G85 automobile and other industrial specifications.
规格
1.Experimental space: 900×600×500(宽×深×高)mm other sizes can be customized
2.Outer space: according to the actual size
3. 电源: 380V 6KW 50HZ MAX 30A
4. Materials:
(A) imported PVC board is adopted in the laboratory, which is acid and alkali resistant.
(乙) imported PVC board in the outer box, resistant to acid and alkali.
(C) the test replenishment tank is equipped with a hidden water table, which is easy to clean and not easy to break.
(D) the saturated air barrel adopts SUS#304 stainless steel high-pressure barrel with the best insulation effect.
5, according to customer test requirements, can be set the salt dry and wet composite test
Salt spray test – moisture/Wet test
(A) brine spray laboratory: NSS, CASS
(1) laboratory: 10℃ ~ 50 ℃
(2) saturated air bucket: 47℃ ±1℃
(乙) moisture test:
(1) 温度: 40℃ ±2℃
(2) 湿度: more than 93%~100%
(3) saturated air bucket: 47℃ ±1℃
(C) drying test:
(1) 温度: 15℃~50℃ ±1℃
(2) 湿度: over 30%
6.Air supply system
The air pressure is 1kg/cm2, which can be adjusted in two stages. The first is the imported pressure regulating filter with the function of filtering water.
Adjust to 2-2.5kg/ cm2 roughly, the second is the imported precision pressure regulating valve, adjust to the pressure gauge 1kg/ cm2.
7.Spray method:
1. Apply bernouldt principle to take and absorb salt water and atomize it, the atomization degree is even, without blocking crystallization, to ensure the standard of continuous test.
2. Nozzle: made of special glass nozzle, the size and Angle of spray can be adjusted.
3. Spray volume: adjustable 1.5± 0.5ml 80cm2/Hr (16-hour average volume).
4. large brine storage tank, 48HR continuous spray.
8.Heating system:
External hot air heating method is adopted to reduce standby time and component damage rate.
S.S.R control heating power, accurate temperature, low power consumption.(titanium alloy corrosion prevention tube for electric heat pipe)
Wet And Dry Combined Salt Spray Tester
1. Circuit control system
2. The main controller adopts 7-inch LCD human-machine interface, and the main screen can plan the test program.
3. The fixed time can be set 0-999 H 59 MIN.
4. The program mode can set salt spray and moisture test at the same time
5. With power off memory device, the remaining program can be continued when power back.
6. The rise and drop of temperature can be used for speed control and self-calibration of temperature and humidity reference points.
7. Temperature and humidity sensor the DIN PT – 100 哦 (铂).
Wet And Dry Combined Salt Spray Tester
Inlet and drainage system:
The water inlet adopts the automatic water replenishment system. When the water level is too low, it will be replenished automatically, and manual water replenishment can be used.
Drainage water pump with acid, alkali and corrosion resistance, increase the service life, reduce the waiting time for drainage.
All pipeline accessories are imported acid-alkali corrosion resistant components, 长寿.
Product link:
https://www.gonoava.com/product/ga-2008-wet-and-dry-combined-salt-spray-tester/
Contact:
电子邮件: arlenliu@gonoava.com
WhatsApp: 0086 18670728798(We chat)
If you have any questions you can send me a message or email.