External chloride stress corrosion cracking (ECSCC) of insulated austenitic stainless steels (e.g. TP304 SS and TP316 SS) can occur when water containing chloride is present underneath insulation, external metal skin temperature exceeds approximately 50 °C, and there is no surface protection or when the protective coating (e.g. paint) is damaged. A thermal sprayed aluminum (TSA) coating can provide a robust barrier preventing corrosive water from reaching the stainless steel metal surface, but can also provide cathodic protection, even when the TSA coating is damaged. Electrochemical tests and slow strain rate tests were performed to demonstrate the protective ability of a thermal sprayed aluminum coating to prevent chloride stress corrosion cracking of TP304L SS in aqueous chloride solutions. In order to compare the application of TSA coatings with other methods to mitigate ECSCC, this paper also discusses alternative mitigation methods.
Keywords: corrosion under insulation, CUI, chloride stress corrosion cracking, austenitic stainless steel, TP 304SS, slow strain rate test, thermal spray aluminum, TSA, electrochemical techniques, polarization, cathodic protection, paint coating, Aluminum foil wrapping, Al foil