EFFECTS OF ROLLING DIRECTION AND TENSILE-STRESS ON THE CORROSION OF A NAVAL CARBON-STEEL IN NATURAL MARINE ENVIRONMENTS .1. NATURAL SEA-WATER

The effect of rolling direction and tensile stress on the corrosion morphology of a naval carbon steel was investigated in continuous immersion tests for a period of about three years in natural sea water in Genoa Harbour. In order to:avoid the effects of macrofouling, the specimens were immersed in tanks containing carefully filtered sea water, periodically renewed, and controlled by monitoring the hydrological parameters, oxygen content and temperature. The experiments were performed on specimens cut both parallel and perpendicular to the rolling direction of the plate, and some specimens were subjected to differing degrees of elongation. The corrosion rate was initially high and decreased to reach stable values between the second and third years of exposure. The rolling direction has a greater effect on the behaviour of the transverse surfaces than on the rolling surfaces. In particular, the transverse surfaces which were parallel to the rolling direction underwent considerable localised corrosion, while those perpendicular to this direction showed zones with uniform corrosion and zones lvhere the attack was localised, but only at an initial stage. The tensile stress lvasfound to have a considerable effect only on those surfaces which, owing to rolling, had become more active, that is, the transverse surfaces parallel to the rolling direction. © 1979 Maney Publishing.