| Abstract: | Forecasting the corrosion susceptibility in the weld zone Forecasting the corrosion susceptibility of a weld seam requires the knowledge of as much data as possible of the material-electrolyte system. Important data are structural changes in the material as a consequence of heat flow during welding. It is therefore important to know the precipitation conditions in materials intended for use in welded structures. A particularly useful tool in corrosion forecasting is the potential probe curve the basic shapes of which and conclusions to be drawn therefrom are described. Its validity is checked using ship steels welded by different methods and being exposed to seawater. It is shown that less noble portions in the potential probe curve are a necessary but not a sufficient condition for selective corrosion. The curves agree with practical experience only when the welded specimens are exposed to flowing seawater. On the other hand, regular shapes of the curve may be taken for a necessary and also sufficient condition for the impossiblility of selective corrosion in the weld zone. As to steels the variety of possible material/electrode combinations may be divided into two large groups: unalloyed steels in aqueous, aerated and near neutral, and stainless steels in neutral and acid media. |
