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Corrosion is a natural process that occurs when materials are exposed to corrosives such as oxygen, acids, ions humidity, high temperatures, sunlight, or various chemicals. Corrosion affects a wide range of materials, including metals, plastics, ceramics, and organic materials.
Corrosion is a major problem for many applications since it negatively affects the structural integrity of the materials and their longevity. In some cases, corrosion may not be visible or it may be difficult to determine the level of corrosion in a material. That difficulty is overcome by various methods of testing material for corrosion and international standards providing guidelines to grade corrosion levels.
Standards of Corrosion Testing
As mentioned previously, assessing the level of corrosion can be challenging. International organizations such as ISO, ASTM International, and NACE international provide important guidelines regarding corrosion testing.
American Society of Testing Materials or ASTM for short, is a leading organization that standardizes countless testing processes and methods for various materials, including corrosion tests. ASTM standards refer to a variety of topics. Here are the relevant ASTM standards for corrosion testing:
ASTM G1-03(2019)
Standard Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens.
ASTM G3-14(2019)
Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing.
ASTM G15-19
Standard Terminology Relating to Corrosion and Corrosion Testing.
ASTM G31-72(2017)
Standard Guide for Laboratory Immersion Corrosion Testing of Metals.
ASTM G46-94(2020)
Standard Guide for Examination and Evaluation of Pitting Corrosion.
ASTM G48-11(2021)
Standard Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chloride Solution.
ASTM G85-11(2021)
Standard Practice for Modified Salt Spray (Fog) Testing.
ASTM B117-19
Standard Practice for Operating Salt Spray (Fog) Apparatus.
ASTM B368-17
Standard Test Method for Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing (CASS Test).
ASTM B380-18
Standard Test Method for Corrosion Testing of Decorative Electrodeposited Coatings by the Corrodkote Procedure.
ISO is another worldwide recognized organization that provides guidelines for corrosion testing. Here are the relevant ISO standards:
ISO 8407:2017
Corrosion of metals and alloys – Removal of corrosion products from corrosion test specimens.
ISO 10271:2011
Corrosion of metals and alloys – Determination of resistance to intergranular corrosion of solution heat-treatable aluminum alloys.
ISO 11503:2021
Corrosion of metals and alloys – Test method for the evaluation of the efficacy of corrosion inhibitors in a laboratory test rig.
ISO 11846:2015
Corrosion of metals and alloys – Guidelines for conducting cyclic corrosion tests for automotive coatings.
ISO 12944-6:2018
Paints and varnishes – Corrosion protection of steel structures by protective paint systems – Part 6: Laboratory performance test methods.
ISO 17475-2:2017
Corrosion of metals and alloys – Determination of dezincification resistance of copper alloys with zinc.
ISO 22479:2021
Corrosion of metals and alloys – Corrosion testing of welded joints.
ISO 9227:2017
Corrosion tests in artificial atmospheres – Salt spray tests.
As suggested by the headlines, the goal of international standards of corrosion testing is to ensure that the tests are conducted accurately thus the results are reliable. Since corrosion is one of the most important factors which affect the structural integrity of systems, therefore safety, accurate testing, and reliable results are exceedingly important.
In addition to the international standards, some industries have developed their own set of testing standards to ensure the utmost safety such as the automotive and the aerospace industry.
To summarize, international and sector-specific standards ensure, the correct preparation of specimens, accurate execution of various testing methods, and correct analysis of data to provide reliable corrosion testing.
Types of Corrosion Testing
There are various corrosion testing methods. Choosing and executing the correct method is crucial to ensure accurate results. In general, corrosion testing methods can be divided into two main categories; laboratory tests and field tests.
Laboratory tests, take place in a controlled environment while field tests are performed on-site. It is safe to say that laboratory tests provide more accurate results due to the tests being conducted in a controlled environment.
Salt Spray Test
Saltwater is one of the most corrosive substances. Materials that are expected to be in contact with saltwater are tested for their corrosion resistance under simulated parameters.
The salt spray test is performed by constantly spraying the sample with a saltwater mist. The level of corrosion and the time it takes the material to corrode is recorded to measure its resistance.
Electrochemical Test
An electrochemical test is performed to evaluate the corrosion resistance of the material caused by acidity and high temperatures. The sample is tested under different levels of electrical current to simulate different acidity and temperature levels.
Immersion Test
The immersion test is the most accurate result for materials that are expected to be fully covered by a corrosive. The process is quite self-explanatory, the sample is submerged in the corrosive, and the effects are recorded.
Crevice Corrosion Test
Crevice corrosion occurs in areas where there is restricted access to oxygen or where there is a concentration of corrosive ions. The crevice corrosion test involves creating a small crevice in the material and exposing it to a corrosive environment to evaluate its resistance to crevice corrosion.
Galvanic Corrosion Test
Galvanic corrosion occurs when two different metals are in contact in a corrosive environment. The galvanic corrosion test involves placing two different metals in contact and exposing them to a corrosive environment to evaluate their susceptibility to galvanic corrosion.
Stress Corrosion Cracking Test
Stress corrosion cracking occurs when a material is under stress and exposed to a corrosive environment. The stress corrosion cracking test involves applying tensile stress to the material and exposing it to a corrosive environment to evaluate its resistance to stress corrosion cracking.
Industries Exposed to Corrosion
Some industries are more exposed to corrosion due to used production techniques and materials utilized. Here are the industries which are the most exposed to corrosion:
- Oil and gas industry
- Maritime Industry
- Aerospace industry
- Automotive industry
- Construction industry
Conclusion Corrosion is an important risk for various industries. The negative effects of corrosion can be devastating and hazardous. That’s why corrosion and its effects need to be constantly checked. In addition, the materials to be used to construct systems with must be selected per their corrosion resistance, if exposure to corrosives is exp
