Evaluation of hydrogen assisted cracking resistance of high strength Jack-up steels

Abstract

The use of high strength steels is very attractive for the fabrication of the legs of Jack-Up platforms, however, there are still some concerns on the possibility of hydrogen assisted cracking resulting from cathodic protection. An experimental programme was performed to assess the hydrogen assisted cracking sensitivity of a high strength steel in conditions of cathodic protection. Hydrogen activity resulting from cathodic protection has been evaluated from electrochemical hydrogen permeation test results and from hydrogen analysis on exposed samples. It is shown that cathodic protection in sea water results in low hydrogen activity. Comparative slow strain rate tests performed on high strength steel and on lower strength materials show that, for a given test condition, comparative behaviour is observed. Fracture mechanic tests indicate that high K ISCC values are obtained under cathodic protection. Finally, tests performed on weld structures confirm that high strength steels are suitable for use under cathodic protection. An increase of the protection potential (from −1050m V/ECS to −850m V/ECS) can still improve the behaviour.