SURFACE HYDROGEN-INDUCED BLISTERING ANALYSIS OF SQUARE PIPE

Blister were observed in the surface of square pipe after being hot zinc-plated. In this paper,blister were analyzed and investigated by means of chemical analysis,metallographic examines and SEM. It was proved through chemical analysis that there existed high concentration hydrogen in plate. And it was observed by SEM and EDX that a great deal of silicate inclusions with lump and lamellar shape nearly took up the interface of blister. And these inclusions distributed with ribbon shape along the rolled direction were also verified by metallographic examine. These provided the basis for hydrogen absorption,aggregation and blister formation. The hydrogen absorption and high level inclusions caused the surface blister of zinc-plate.