Posted by Gordon England on March 12, 2003 at 02:02:31:
In Reply to: plasma coatings / HVOF coatings posted by Vinod Hoskote on March 09, 2003 at 12:26:11:
: I have a problem of not being able to strip away the Plasma / HVOF coatings on contoured parts that have come for hard chrome electroplating .Previous coatings have to be removed before electroplating.
: I have tried electrolytic removal of coating. even a 50 percent hydrochloric acid dip did not remove anything from the surface.
: I do not know the exact composition of the coating.--could be carbide or ceramic.
: The question is how do i remove it.
: regards.
: Vinod Hoskote
: email: blibr92@emirates.net.ae
Hi Vinod
This is difficult to answer without knowing the coating and substrate materials.
You could try (with care!)
Electrolytic method:
20% sodium carbonate
5% tartaric acid
75% water
temperature 70-80 degree C
Stainless steel cathode, coated part anode
current density 4-8 amps/sq in @ 6 volts DC
Chemical/mechanical method:
30% sodium hydroxide
70% water
temperature 40 degree C
time 30 minutes
Grit blast
repeat steps if necessary
Mechanical methods such as grit blasting or very high pressure water jet blasting may be necessary if chemical or electrolytic methods fail.
Regards Gordon
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