Surface Modification of Stainless Steel by an Alternating Voltage Process.

In a program which is devoted to the development of methods of corrosion protection which do not rely on environmentally hazardous chemicals such as hexavalent chromium ions, the authors have recently demonstrated the use of surface modification for improved corrosion resistance of Al alloys. The Ce-Mo process consisting of electrochemical and chemical steps has been used to produce stainless aluminum. At present they are evaluating an electrochemical process for surface modification of stainless steel. Initial results obtained for stainless steel (SS) type 304 are presented in this communication. An alternating-potential-step (AV) passivation process is described which has been applied in an acid medium to stainless steel type 304. The corrosion resistance as determined by open-circuit potential decay, recording of anodic polarization curves, and impedance spectra is greatly increased by the AV passivation process especially when a post-treatment in an inhibitor solution is added to the process.