If you’re a Sharretts Plating Company customer or a regular reader of our newsletter, you know that electroplating is a highly effective metal finishing process. But you might not be as familiar with electropolishing, which is often used for surface improvement on many types of metal parts and components, particularly those made of stainless steel.
Electropolishing can be viewed as the opposite of electroplating. While the latter involves the depositing of a metal coating on a surface, the former entails the removal of metal and other materials from the work piece.
Basic Electropolishing Process
With electropolishing, the metal piece is fitted with two electrodes. One serves as the anode and the other serves as the cathode — they are connected to a DC power supply. The piece is then immersed into a bath comprised of a specially formulated, temperature-controlled electrolytic solution. The activation of the power supply produces an electrical current that passes from the anode to the cathode, resulting in the oxidation of the metal surface and the removal of surface impurities and irregularities.
What Are the Benefits of Electropolishing?
- Bright finish — Perhaps the most noticeable benefit of electropolishing is that it provides an immediate brightening of a metal finish. By eliminating or minimizing stains, heat discoloration and minor scratches, electropolishing can bring out the metal’s natural shine, which enhances the appearance of the piece.
- Increased corrosion protection — By removing surface imperfections, electropolishing can increase the piece’s resistance to corrosion. That’s because the elimination of imperfections can prevent the moisture that leads to corrosion from accumulation. In fact, some salt spray tests have indicated that electropolished pieces experience greater corrosion resistance than passivated and raw parts.
- Ultracleaning — Electropolishing offers remarkable ultracleaning capabilities through the removal of rust, imbedded scale and other foreign debris. This can be accomplished without stressing the piece or negatively impacting surface hardness and integrity.
- Improving microfinish — Electropolishing can effectively remove the microscopic peaks resulting from processes such as welding, forming and stamping. The reduction of microfinish values and accompanying increases in surface smoothness can be extremely beneficial in the production of valves and gears.
- Edge break removal — The ability of electropolishing to remove surface metal from a part makes it extremely effective in the elimination of edge breaks. That’s why electropolishing is often preferable to vibratory finishing or tumbling for use on delicate parts.
- Surface preparation — Because electropolishing creates a smooth, clean surface that promotes adhesion, it is sometimes used to prepare surfaces for processes such as e-coating, plating, welding and anodizing.