Influence of cathodic-protection-induced hydrogenation on mechanical properties of two ship hull plate steels

Abstract

Tensile testing and Charpy V impact testing results for two ship hull steels: an ordinary strength steel grade A and a higher strength steel grade AH32 each in both as-received conditions and in hydrogenated by zinc protector in salt water conditions. For both steels the hydrogenation has slightly increased yield stress (R_e) and elongation (A) and has not influenced ultimate tensile strength (R_m), while reduction of area has been unchanged (A steel) or even decreased (AH32 steel) due to the hydrogenation. The effect of the hydrogenation on Charpy tests results has evidently been beneficial: the increase of Charpy energy and of percent fibrosity (ductility) of fracture appearance as well as a shift down of ductile-brittle transition temperatures have been observed. It seems that the present practice to evaluate the mechanical properties of ship steels by testing the specimens without hydrogenation leads to conservative results. The Authors have hypothesized that the beneficial effect of hydrogenation can occur if the deformation rate is fast enough, the notch is sharp enough (although only for specimens hydrogenated in unstressed conditions) and hydrogen concentration is moderate.