US1794929A - Method of fractionally plating objects - Google Patents

Description

Patented Mar. 3, 1931 PATENT OFFICE VICTOR L. SODERIBERG, OF DETROIT, MICHIGAN METHOD OF FBACTIONALLY PLATING OBJECTS Ho Drawing.

It is frequently desirable to electroplate parts of an object with chromium while other parts, on which metal will be deposited when Screw threads, in many instances, and 'fin-' ished surfaces adapted to makefine fits or form elements in joints or partsof tools and dies should be left in a virgin state. When such surfaces are plated with chromium there is a waste of energy and material as well as, in most instances, an actual objection to the presence of plate.

The object of the present invention is to 2 produce a simple and novel method of plating with chromium only those areas on which plating is desired, even though there are adjacent or other areas which, in ordinary practice, would become plated.

I have found that if those areas that it is desired to leave free from plate and which would otherwise receive a deposit of metal during the plating process, are covered with an electrically-insulating substance insoluble in the plating bath, the covered surfaces will not become plated in the subsequent electrodeposition process. The protective insulating covering should preferably, however, be

soluble in removers, that is, compounds of some kind for removing them after the plating process is completed.

Any cheap nitrocellulose lacquer may be used advantageously for the protective covering, as will also liquid glass compounds as for example so-called water glass, in the process of chromium plating. Other substances may also be us ed,-.provided that they will not harm or throw anything of a hamful, poisonous or detrimental nature into the chromium plating solution.

The covering of large areas is particularly advantageous in chromium plating where heavy currents are r uired, as the currents are thereby localized 1n the areas requiring 59 .plating and much less current is required Application filed Kay 7, 1927. Serial 30.189344.

than woud be the case if no protective coating were employed. Furthermore, in the pres ent state of development of the art of chromium plating, if the anodes are so placed as largely to concentrate the current in the areas which it is desired to plate, the other areas often become etched due to the inefficiency of the chromium bath. The protective insulating coating prevents such etching and a higher efficiency of the specially-placed e anodes results. Again, wherethe currents are localized as far as practicable, there will still be more or less platmg on the areas which should be left unplated, such plating being streaky and uneven; this objection being also overcome by the use of the protective coverafter the areas that are to be left unplated have been properly covered with the insulating material and preferably after the insulating material has dried, the plating process is carried on in the usual Way, with the result that the unprotected areas receive a deposit of metal, whereas the insulating material prevents any plating of the surfaces covered thereby.

. When the plating operation has been completed the insulating material may be removed or not, depending on the nature of the work and the uses to which it is to be so put.

. ab e manner.

In testimony whereof, I sign this specification. 1 4 VICTOR L. SODERBERG.