Historical Articles

October, 1952 issue of Plating

 

QUESTION BOX

Readers’ questions of general interest

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Q. 145. Will you send us as much information as possible regarding the exact procedure to hard chromium plate to a thickness of 0.010 inch on 18 and 8 stainless steel?

A. The best way to handle stainless today is by using the new Unichrome plating solution. If this is not available, then reverse etch in a chronic acid etch bath at 100 a.s.f. for 1-5 minutes, depending upon what gives the smoothest results. Then treat as an “add-plate” job; that is, build up the current density in the plating solution very slowly over a period of 15 minutes, to the regular plating current density.—ART LOGOZZO.

Q. 146. We manufacture a product that consists mainly of small aluminum stampings that should be brightened by a chemical dip. Could you advise us as to sources of such material?

A. The subject of bright dipping aluminum was discussed at the Milwaukee Convention of the A. E. S. I and reported in the 36th Annual Proceedings (1949), page 163 et seq.—D. G. FOULKE.

Q. 147. For the past several months we have been brass I plating a zinc die cast handle and obtaining very good results. However, due to the addition of another machining operation we must now replate these handles. Is it necessary to strip the brass from the handles in the replating process or can we replate without stripping?

A. The practical solution to this problem is to follow a finishing cycle similar to that required when the piece was originally finished.... A copper flash must be used in order to insure adhesion over the machined areas exposing the die cast metal.

A more concise answer cannot be given as the question is not detailed with such comments as to thickness-of plated coatings, or whether the parts are polished, lacquered, or other condition.

Stripping of brass plate with a copper undercoat from zinc die castings can be done electrolytically with ortho-phosphate solutions that deplate the brass and copper, and passivate the zinc so no etching occurs or I by oxidation processes such as the sulfide solutions both of the above made and sold by various chemical houses under their own trade names.—GEORGE F. HERRMANN.

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