If you are a user of protective coatings in the construction, manufacturing or engineering industry, there is one aspect of corrosion science that requires your careful understanding – that is the role and limitations of accelerated corrosion testing.
For decades, the so-called ‘salt spray test’ has generated misleading information about coating performance and its results still feature prominently in the marketing materials of products that, artificially, yield more favourable outcomes than in the real world.
So what is wrong with the ‘salt spray test’?
Firstly, the test does have some value for quality control of a specific material or coating. This is what the test was originally designed for and it is used successfully by some industries for this purpose. Although, it is now largely abandoned even by the automotive industry.
The serious misuse of the ‘salt spray test’ is its use to compare, or rank, different materials or coatings that have differing characteristics. It is especially misleading to use the test to compare paints with metallic coatings. It is equally misleading to compare different metallic coatings. For example, comparisons between zinc and zinc alloy coatings (such as those containing small additions of magnesium and aluminium) can produce comparative results that are vastly different to real in-field performance...