While aluminum alloys are naturally resistant to corrosion, they’re not invulnerable to it. This reality raises a key question: How can you determine aluminum’s resilience and resistance to corrosion when extreme temperatures and moisture combine? The answers start through reliable CASS testing.
Whether a CASS test is entirely new to you or you’ve heard about it before but only in passing reference, the following will help you understand more about this unique testing procedure, why it’s performed and how the test method is carried out.
What is a CASS test and what does CASS stand for?
Short for Copper Accelerated Salt Spray, a CASS test is an accelerated corrosion test that uses a combination of sodium chloride and water to, in effect, simulate the manifestations of corrosion, which helps determine the test subject’s corrosion resistance. The main difference between a CASS test and a regular spray fog test is the composition of the test subject, which is usually aluminum or an aluminum alloy.
In addition to evaluating the corrosion resistance of aluminum alloys, the CASS test is also used for verification purposes. More specifically, it assesses the presence of nickel and chrome when used as a means of plating. Products that often receive chrome plating include high-powered equipment, stainless steel and automobiles.
How is a CASS test conducted?
A CASS test has many similarities to the standard salt spray test. For example, it typically uses the same break down in how many parts are water (95%) and how many parts are sodium chloride (5%). As SGS explains, a CASS test also uses reagent grade copper chloride as an added ingredient, which serves as a dehydrating element. The reagent grade copper also affects the pH level of the solution, moving it from a neutral 6.5 to 7.2 to somewhere between 3.1 and 3.3, which makes the solution much more aggressive before spraying begins.
Upon atomizing the solution, the mist is dispensed evenly as an acid salt spray fog. The test itself occurs within a test cabinet, which allows for simulated service evaluations that can be customized and expedited.
In terms of how long CASS tests last, they generally run no fewer than 24 hours, but they can be 48 hours or longer as well. However, the abrasiveness of the salt spray is such that the CASS test tends to be shorter than the standard salt spray test.
Why are salt spray tests even necessary?
It isn’t so much a matter of if a metallic product will corrode, but when. A salt spray test may not be a perfect predictor of when corrosion will take place, but it can give you a general idea of what conditions will lead to observable wear and tear and offer insight on what coatings may be best to delay its development.
As a hardcore solar mounting system player, Solaracks’ fastening products often works with SGS for the anti-corrosive test, to ensure the surface treatment will last under various conditions. We leverage the very latest in research and development to provide results that you can trust.