Technical Note: The Effect of Rotation on Pitting Behavior of Aluminum and Stainless Steel Available to Purchase

The authors have recently evaluated the effect of the relative velocity metal/electroiyte on galvanic corrosion of Al alloys¹  and 4340 steel²  in 3.5% NaCl and ASTM substitute ocean water (ASTM D1141) using a rotating cylinder arrangement. It has been found that, in general, corrosion rates of single metals and anodes in galvanic couples increase with the square root of velocity similar to the increase of the limiting current density for oxygen reduction. It was of interest to determine the pitting behavior of several materials in the same media in order to evaluate the possibility that rotation of the electrode leads to removal of the acidic solution, which is concentrated in metal chlorides from the pits, and thereby to changes in pitting behavior. Franz and Novak⁴  have found that increasing the rotation speed of Al disc electrodes makes the pitting potential more noble. During the initial phase of...