What are some causes for pitting of 316-SS when it is electropolished? B. B.
Two of the most likely causes for this behavior are substrate problems and cleaning of the substrate prior to electropolishing. In the former category are inclusions that can occur during the milling process or localized overheating during the machining process.
If the cleaning step is at fault, you must review your cleaning process steps and confirm that the cleaning materials are not “over the hill.” One of the most common problems of metal finishing is the lack of attention to the cleaning process. Assuming your cleaning process is satisfactory, try dipping the part in concentrated nitric acid before the electropolishing step.