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Remove smut in Allen Key hole after hydrochloric acid etching





October 2, 2010

I have been doing hard chroming works for some time and recently, I received a high volume order to flash chrome commercial allen key screws. The only problem I faced is to chrome the Alan Key screw's hole, it is where the current density is extremely low due to the recess. After trying using high or maximum current available with 1000 A rectifier, the recess can be chromed, provided that the holes are polished with scotch brite, but this addition operation causes lost time.

I would to know: Is there any method that using chemical or electrocleaning to remove the smut in the holes without mechanical polishing?

I have tried using reverse electroclean using sulphuric acid as medium, the results are good, it means the screws are very clean, but the method caused loss of tensile strength of the material. Screws breakages have occurred.

San Guan Ooi
Plating shop owner - Bangkok, Thailand



October 19, 2010

Gentleman,
Use the following sequence.
Soak Degrease, Descale in Alkali pot. permanganate anodic, Pickle in HCl, Degrease/Derust Anodically, Mild acid dip and follow the plating sequence.
This will help you to come out of the problem. All the best

NARYANASWAMY SHANKARANRAYANAN
- Bangalore, Karnataka, India


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