Effect of Cu on the Hydrogen Induced Cracking of the Pipe Line Steel

The effect oj Cu Oil the hydrogell illduced cracking oj the pipe line steel was studied electrochemically and metallographically ill detail.It was Jound out that, if the addition oj Cu was more than 0.2 % , hydrogen illduced crackillg could be effectively suppressed.This is because addition oj Cu enhances the Jormation oj tight and adherent suiface film.This film was Jound to be quite protective, decreasing the corrosion rate greatly.As a result , the volume oj the hydrogen evolved at the steel suiface could be appreciably lowered.This suiface film was Jurthermore JOllnd to be quite impermeable, so that hydrogen can hardly enter into the steel.Critical concentration oj hydrogen that causes cracking cannot therefore be established in the Cu bearing steel.From these results, it is suggested that suiface film control by alloying may be one oj the most 4fective method in /JTeventillg hydrogen induced cracking.