What Does Pitting Test Mean?
Pitting tests are used to evaluate the likelihood of a metal developing localized corrosion in the form of holes on its surface. Pitting tests are conducted with the use of various metal and solution combinations according to a governing standard (ASTM G48). The selected metal or solution serves as a reference point in order to minimize data inconsistencies and ensure precision.
Corrosionpedia Explains Pitting Test
Pitting tests are used to evaluate the quality of metal resistance against both pitting and crevice corrosion. These two types of corrosion are dangerous as they often lead to structural instability and collapse. Crevice and pitting corrosion are formed due to a localized collection of corrosion-causing agents such as low pH acids, water and salt solutions.
The resistance of a metal to crevice and pitting corrosion can be empirically determined and ranked relative to a critical crevice temperature (CTT) according to the ASTM Standard G48-03. This standard is the Standard Test Methods for Pitting and Crevice Corrosion of Stainless Steels and Alloys by Use of FeCl3. The standard recommends six methods of implementation. The various method purposes are:
- Method A - To determine the relative pitting resistance of stainless steels and nickel-base, chromium-bearing alloys
- Method B - To determine the pitting and crevice corrosion resistance of stainless steel alloys
- Methods C, D, E and F - For ranking of alloys by minimum (critical) temperature to cause initiation of corrosion. This applies to stainless steels, nickel-base and chromium-bearing alloys in a standard ferric chloride solution.