Characteristics of Electrolytic Polishing
In an electrolytic polishing solution tailored for each metal, when direct current is applied with the metal as the anode, the metal surface undergoes a smoothing and polishing process as the metal dissolves. This phenomenon, known as electrolytic polishing, is particularly used on austenitic stainless steels (such as SUS304 and SUS316) and aluminum.
Unlike mechanical polishing (which removes surface imperfections through abrasives and pressure, such as with grinders, sandpaper, or buffs), electrolytic polishing smooths and polishes the surface by preferentially dissolving the protruding areas. This process results in a clean surface without leaving any "burn" marks or residue, and without creating a "deformation layer." It is a highly "clean" polishing method, ensuring a smooth and glossy finish without contaminants.
Characteristics of Chemical Polishing
Chemical polishing is a process in which the metal surface is dissolved through a chemical reaction by immersing it in a special solution. Like electrolytic polishing, chemical polishing is used for stainless steel components, but it is particularly suited for removing foreign matter, scale, and cleaning the surface of complex-shaped stainless steel parts.
Buff Polishing
Buff polishing typically involves using cloth cut into circular shapes and sewn to a specific thickness, or fabric sewn at a bias, with polishing compound applied to the outer surface. This method is used to polish the product. Unlike grinding (such as with grinders), buff polishing focuses on polishing the surface layer of the workpiece.
The process generally starts with coarse polishing (rough polishing) to remove larger imperfections, followed by several finishing stages to achieve a high-gloss final finish. The most common approach includes multiple steps, with the final step producing the desired shiny surface.
Electrolytic Polishing
| Benefits and Advantages | Challenges |
|---|---|
| The process preferentially dissolves the protruding areas of fine surface irregularities, resulting in smoothing and polishing. It also removes contaminants, foreign matter, and any altered surface layers generated during physical polishing, such as buffing. By leaving the polished surface in a clean state, this process promotes the formation of a stronger passive oxide layer, significantly improving corrosion resistance. |
Compared to mechanical polishing methods like buff polishing, this process is not suitable for removing large surface irregularities, high roughness, or substantial burrs. Uneven electrical current flow can cause whitening, cloudiness, or unevenness on the surface. To achieve optimal smoothing and gloss, it is recommended to first perform buff polishing or a similar process to moderately smooth the surface before applying electrolytic polishing. |
Chemical Polishing
| Benefits and Advantages | Challenges |
|---|---|
| By dissolving the surface, this process creates a clean finish while removing fine irregularities to achieve smoothing and gloss. Since it relies on the chemical action of the solution without applying electrical current, it is less prone to causing unevenness and can accommodate complex shapes. |
Since smoothing and polishing result from the dissolving power of the chemical solution, as the process progresses (dissolving iron, nickel, and chromium), changes in the solution alter the dissolution pattern. Therefore, continuous solution management—including regular replacement and disposal—is essential. |
Buff Polishing
| Benefits and Advantages | Challenges |
|---|---|
| It can transform rough or uneven surfaces into a glossy finish and remove large burrs created by processes such as pressing and cutting. |
Abrasive grains, buffing residue, oils, and compounds often remain on the surface, making it difficult to remove embedded particles and metal fragments, which can cause corrosion. Fine irregularities and polishing marks are also left behind, providing sites for contaminants to adhere. For applications requiring high cleanliness, this untreated surface condition is unsuitable. |