Thermally Sprayed Aluminum Coatings for the Mitigation of Corrosion and Environmentally Assisted Cracking of Welded Duplex Stainless Steel at Elevated Temperature

摘要

Duplex stainless steels are susceptible to localized corrosion and environmentally assisted cracking when subjected to loads and temperatures approaching their material design limits. Conventional organic coatings provide limited mitigation due to their rapid degradation at elevated temperature. Whilst the use of thermally sprayed aluminum (TSA) to mitigate the corrosion of C-steels and austenitic stainless steels is well-documented, there are little or no published data relating to its behavior on duplex stainless steels (DSS) or other high strength alloys. This paper summarizes the results of a Joint Industry Program which comprised a detailed evaluation of the performance of TSA-coated, 22Cr DSS substrates conforming to UNS 31803 including welds subjected to pitting corrosion, external chloride stress corrosion cracking and hydrogen cracking. The effect of plastic strain (at values simulating pipe reeling) on TSA coating integrity and behavior was investigated. TSA corrosion rate data were produced at ambient and elevated temperature using two electrochemical techniques. The effects of sealant selection on TSA coating behavior were characterized. Recommendations for the application of TSA coatings on 22Cr DSS are provided.