US3794570A

US3794570A - Electroplating chromium with a nonconsumable chrome plating anode

Info

Publication number: US3794570A
Application number: US00279947A
Authority: US
Inventors: H Manko; J Langan
Original assignee: Alpha Metals Ltd
Current assignee: Alpha Metals Ltd
Priority date: 1972-08-11
Filing date: 1972-08-11
Publication date: 1974-02-26
Anticipated expiration: 1991-02-26

Abstract

A NON-CONSUMABLE CHROME PLATING ANODE WHICH IS AN ANODE SHAPED LEAD BODY, WITH NOT LESS THAN 20 P.P.M. CALCIUM AND UP TO APPROXIMATELY 3% TIN ALLOYED WITH THE LEAD.

Description

United States Patent ELECTROPLATING CHROMIUM WITH A NON- CONSUMABLE CHROME PLATING ANODE Howard Manko, Teaneck, and James Langan, Bayonne,

N.J., assiguors to Alpha Metals, Inc.,.Huds'on County,

No Drawing. Filed Aug. 11, 1972, Ser. No. 279,947 Int. Cl. C23b 5/ 06 US. Cl. 204-51 I 4 Claims ABSTRACT OF THE DISCLOSURE A non-consumable chrome plating anode which is an anode shaped lead body, with not less than 20 p.p.m. calcium and up to approximately 3% tin alloyed with the lead.

BACKGROUND OF THE INVENTION Field of the invention This invention relates generally to non-consumable chrome plating anodes and particularly to such anodes which are highly resistant to deformation in shape under varying conditions of temperature operation, and have the further characteristic of forming thereon a benevolent, adherent scale, said scale contributing substantially to the extended life of the anode.

Description of the prior art Numerous anodes are available for electroplating of chrome. It is frequently found that heat required during the electrodeposition process causes a physical deformation of the anode, which initially may move portions of the anode away from the work piece, thereby retarding the rate of deposition, and move other portions of the anode toward the work piece, thereby accelerating the rate of electrodeposition. The net result is an uneven rate of electrodeposition, in many instances of highly unsatisfactory character requiring the rejection of the plated work piece. Further deformation of the electrode may actually bring it into physical contact with the work piece, shorting the circuit with catastrophic results. Conventional anodes frequently accumulate scale which is of such a character that it impairs the process of electrodeposition. The character and quality of such scale is well-known to those who practice the art of chrome plating. During down time, the electrodes are usually removed from the bath for the purpose of removal of scale. If it is not removed, the scale may deteriorate, or it may be necessary to de-plate it. It becomes apparent that an ideal chrome plating anode would be one which would not deform, would not be subject to deleterious scaling during down time, and would have a vastly extended life.

SUMMARY OF THE INVENTION It has been found that a chrome plating anode could be devised which has many of the desirable characteristics in a very high degree. This anode is composed principally of relatively high purity lead containing not less than 20 p.p.m. calcium. The lead is preferably alloyed with ap proximately /2 to 7% of high purity tin. The presence of the tin has a marked effect upon the scale formation on the anode. In the total absence of tin, the full potential of the anode is not reached. The scale formed is thin, less adherent and the lead body is more rapidly consumed during the course of the electrodeposition process. On the other hand, even without the tin, the anodes with the fractional presence of calcium is a considerable improvement over the conventional chrome plating anode. However, with the addition of the tin in 3,794,570 Patented Feb. 26, 1974 the preferred range referred to, a benevolent scale is formed on the anode which does not interfere with the rate of electrodeposition to any substantial degree, the scale is intimately adherent and is not readily discharged and forms a highly protective shield for the anode which vastly extends its useful life over what may be expected from a conventional anode. The character and quality of. the scale is not such as to cause an extensive heat build up in the body of the anode and the alloy of tin and lead is stable dimensionally due to the presence of the calcium so that deformation is not a problem.

PREFERRED EMBODIMENTS A typical chrome plating anode as used in industry is two inches in diameter and may vary from six inches (used for chrome plating the interior of internal combustion engines and cylinders to impart hardness) to twenty two feet (used for plating of decorative structural parts). Intermediate of these extremes would be a six foot anode two inches in diameter used for chrome plating of automobile bumpers. The anode may be prepared by either casting, extruding, rolling, drawings, extending, forming, cladding or any other suitable manner.

The anode is prepared by any of the above well-known methods. The anode requires no particular chrome plating bath to function (excepting, however, chloride base electrolyte baths) and any of the well known electrolytes 1n current use for chrome plating will function satisfactorily. No additives are required to enhance the plating operation or the brightness, because of the special qualities of the anode. The price of the anode presents a great economy due to its vastly extended life and low cost composition, for it may be expected to serve under ordinary circumstances for periods of up to ten years. The plating produced has a high degree of uniformity, free of burns and visible surface imperfections commonly referred to as treeing. The choice of appropriate current density and the concentration of materials in the electrolyte, the presence of additives are all matters which are well known to those skilled in the art and need not be varied to suit the present electrode.

What is claimed is:

1. The method of chrome plating with a non-consumable plating anode subjected to scale formation and temperature variation during a chrome plating operation comprising:

(a) preparing a plating anode consisting essentially of 20 p.p.m. calcium and the remainder lead, and

(b) electrodepositing chrome on a workpiece with the anode.

2. The method of chrome plating with a non-consumable plating anode subjected to scale formation and temperature variation during a chrome plating operation comprising:

(a) preparing a plating anode consisting essentially of 20 p.p.m. calcium, about .57% tin and the remainder lead, and

(b) electrodepositing chrome on a workpiece yvith t1 1e V anode.

3. The method of chrome plating with a non-consumable plating anode subjected to scale formation and temperature variation during a chrome plating operating comprising: g

(a) preparing a plating anode consisting essentially of 20 p.p.m. calcium, about 25-35% silver, and the remainder lead, and

(b) electrodepositing chrome on a workpiece with the anode.

4. The method of chrome plating with a nonconsumable plating anode subjected to scale formation and temperature variation during a chrome plating operating comprising:

20 p.p.m. calcium, about .57.0% tin, about .25-

3.5% silver, and

the remainder lead, and

(b) electrodepositing chrome on a workpiece with the References Cited UNITED STATES PATENTS Betterton et a1 75167 Shoemaker 75167 Eldridge 204-293 X FOREIGN PATENTS 5 anode.

Germany 204--293 US. Cl. X.R.