For all metal coloring and electroplating a clean metal
surface is essential. The cleaning process must remove mineral oils, organic
oils and greases as well as traces of chemicals on the surface. It must
remove oxidation which might interfere with the metal coloration or plating
adhesion and it should possible activate or roughen the metal surface
to better receive the treatment.
Cleaning may be accomplished using mechanical (abrasive),
chemical (heating, solvents, pickling with acids) and electrolytic (electrocleaning,
electrostripping) means. Examples of easily achieved clean surfaces include
sandblasted ones and ones scrubbed well twice with rinsings using Fantastic®.
A pumice rub followed by scrubbing with dishwashing liquid and ammonia
on a toothbrush does pretty well. Best of all is electrocleaning.
A simple procedure is:
- 1.0 Anneal and pickle in suitable
- 1.1 Rinse 3-5 times in running water.
- 1.2 Dip into simmering ammonia and
detergent solution and scrub well.
- 1.3 Rinse well 5 - 10 times.
can be used after step 1.3. While steps 1.0-1.3 produce a quite clean
surface by themselves if one is electrocleaning it is not a bad idea to
pre-clean using steps 1.0-1.3 so as to make the electrocleaning solution
last longer and lower it's work load in cleaning the metal surface.
A much better and surer procedure is:
- 2.0 Remove oxides with pumice.
- 2.1 Rinse well.
- 2.2 Electroclean for 1.5 - 2.5
minutes, object as cathode, then reverse the polarity for a few seconds.
- 2.3 Rinse 3- 5 times in running
- 2.4 Dip in 1:10 sulfuric acid to
neutralize the electrocleaning solution and activate surface.
(15 seconds or so).
- 2.5 Rinse 3 - 5 times in running
After cleaning, the metal should be placed in running
or circulating water (preferably distilled) to avoid oxidation until it
is plated or coloured. One can of course plate or colour immediately after
cleaning. In all cleaning methods the piece must either be wired to suspend
it in the solution or held with tweezers. It must afterwards be very well
rinsed to remove all traces of cleaning chemicals. Do not touch the surface
once it is free of grease.
Note: Sand blasting
may be substituted for steps 1.0 and 2.0 above.
Sample Electrocleaning solution:
| Current density: 1-3A/dm Polarity:
1 - 3
minutes Cathodic (of work)
5 - 10 seconds Anodic
|| 25 grams
|| 25 grams