Knowledge of Electropolishing Processes

Knowledge of Electropolishing Processes (Part Three)
Posted: Dec 18, 2017   Hits: 706
5. Why are there white strips on the surface of the workpiece after the electropolishing process?
Analysis of causes: Relative density of the solution is too high and the liquid is too thick. The relative density is greater than 1.82.
Solutions: Stir the solution more. If the relative density of the solution is too high, dilute the solution with water to the relative density of 1.72. Heat the solution at the temperature of 90 to 100℃ for one hour.
 
6. Why the partial surfaces of the workpiece lack of gloss after the electropolishing process? 
Analysis of causes: The workpiece is not aligned with the cathode, or the workpiece shields each other. 
Solutions: Adjust the position of the workpiece, so that positions of the workpiece and the cathode will be appropriate and the distribution of electricity will be reasonable.
 
7. Why are some parts of surfaces of the workpiece not bright after the electropolishing process?
Analysis of causes: Probably, the generated bubble on the surface of the workpiece is not able to separate from the surface in the later period of the electropolishing process, resulting in the bubble adhering to the surface. Or there are air flow lines on the surface.
Solutions: Make the current density higher, so that amount of evolved gas will be increased to make the bubble fall. Or increase stirring speed of the solution in order to make the solution flow more. 
 
8. Why the contact part of the accessory and the rack isn’t bright and has brown spots, while the rest of the surface are bright? 
Analysis of causes: The reason may be that the accessory is not in good contact with the rack, resulting in uneven distribution of the current, or the accessory is not in much contact with the rack.
Solutions: Polish the contact part of the rack so as to make the electric conduction well or increase the contact area of the part and the rack.
 
9. Why are some parts bright and other parts are not bright or partial parts are not bright in the same tank?
Analysis of causes: The workpiece in the same tank is too many, which will lead to uneven distribution of the current. Or the workpieces overlap with each other.
Solutions: Reduce the amount of the polished workpieces in the same tank or pay attention to the position of the workpiece.
 
10. Why do the concave part of the polished part and the contact point of the part and the rack have silvery white spots?
Analysis of causes: The reason may be that the concave part of parts was blocked by parts itself or the rack.
Solutions: Appropriately change the position of the parts, so that the concave parts can get power lines; reduce the distance between the electrodes or increase the current density.
 
11. Why are there more or less over etchings on surfaces of parts after the electropolishing process even if we strictly follow the process specification?
Analysis of causes: The reason may be that temperature of the solution or current density is too high. If the solution doesn’t have any problems and you have strictly conformed to the specification, the problem might be treatment before the electropolishing process. 
Solutions: Strictly conform to the operation of pretreatment of the electropolishing process. Avoid over etchings in the acid pickling process. Do not leave cleaning water on the surface of the part and then bring water on the surface of the part to the polishing tank.
 

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