The Basics of Testing for Corrosion Resistance (Salt Spray, Humidity, Copper Sulfate)
Corrosion is the gradual breakup of a material due to chemical reactions with its environment and refers to the oxidation of metals. One example is rusting, which is the formation of iron oxides. This can damage the metal, reduce the tensile strength, alter its appearance, and increase its permeability.
There are a number of very effective methods of testing for corrosion resistance. If performed correctly, processes such as Salt Spray, Humidity, and Copper Sulfate testing can deliver very accurate and defined results. Depending on industry requirements, these tests can be subject to very stringent standards and guidelines that require various levels of verification.
A primary testing method is Salt Spray testing, which as its name indicates, evaluates how resistant a part or material is to corrosion when exposed to a salt spray for extended periods of time. Effective Salt Spray testing must be performed in a controlled environment, such as a closed salt fog tank. Inside of the tank, the sample is exposed to a mist of sodium chloride, making the tank’s atmosphere extremely corrosive. By controlling the tank environment, the test can be adapted to replicate many different conditions.
Within the same testing apparatus, Humidity Testing can also be performed. This is a critical test because it defines a part’s resistance to corrosion from humidity alone, which is an important factor when determining a coating selection, as well as life span calculation.
When a more aggressive testing approach is required, Copper Sulfate testing can be used as an alternative to standard salt fog testing. Some of the uses for Copper Sulfate testing are for testing the corrosion resistance of plated and passivated parts; however, it is also used to test high strength and hardened alloys. Because of its aggressive nature, it can find defects more easily than in standard methods, overcoming the corrosion resistance imparted by plating or alloy composition.
As part of our full service testing capabilities, at Pacific Magnetic & Penetrant, we provide Corrosion Resistance testing that can meet the most stringent industry standards. To learn more, contact us directly.
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