Summary for high voltage rust on screws Discussion
High voltage rust on screws is the issue in this thread: Rathi Ramasamy reports that mild steel screws with zinc and blue passivation develop red rust within 15 days after a 35 kV test is applied through a polycarbonate cover. H.R. Prabhakara suggests the most likely reason is electrical discharge during the test, which may puncture or damage the protective zinc coating and allow corrosion to start. His advice is conditional: this explanation assumes the zinc plating itself is otherwise satisfactory. The thread does not offer a full corrective process, but it points to the test method and possible coating breakdown as the first place to investigate before assuming the plating quality is at fault.
Q. Right now the screws which we use in our product are mild steel with zinc and blue pasivation. The issue is when we test our product for high voltage, 35 kV (the voltage is applied on the poly carbonate cover over the screw), we get red rust on the screws within 15 days. Can anybody give the reason and a good suggestion
Rathi Ramasamy
engineering – Tirunelveli, India
A. There could be electrical discharges during testing which puncture the protective zinc coating. This assumes that zinc plating is satisfactory otherwise.
H.R. Prabhakara – Consultant
Bangalore Plasmatek – Bangalore Karnataka India
November 27, 2012