Machine shop finds gold-plated opportunity with selective plating

Modern Machine Shop, May, 1995

Somewhat ironically, Mr. Feher's customer had a chronic problem with damaged pump shafts in its production plating operation. The pumps were used to circulate tank plating solutions. When the pumps were idle, acid would seep through the seats to the bearing. Upon start-up, the bearing would spin and gouge the pump shaft. Initially, Mr. Feher considered flame spray metallizing to repair the shafts. However, the intense heat generated by flame spraying would almost certainly have damaged the rubber and modified Teflon impellers and distorted the shaft. Feher Machine's first repair attempt was with cold epoxy, which eventually worked loose and was pulled into the Teflon impellers.

Having had some conventional tank plating experience, Mr. Feher knew that nickel plating would be an effective solution to the problem. But the cost of disassembling the pumps and sending the shafts out would be prohibitive. After some investigation, Mr. Feher became convinced that the shafts could be plated in-place using a portable selective plating system provided by Sifco Selective Plating of Cleveland, Ohio.

After three days of training at Sifco's Cleveland headquarters and an investment in a Sifco 60-ampere Calcuplate power pack, plating solutions, and some accessory hardware, Feher Machine was ready to perform what was to be their first of many successful in-place plating repairs.

Selective electroplating, often called "brush plating," is the process of applying a metal deposit to a selected, or localized, surface on a workpiece without using an immersion tank. According to Sifco's Technical Coordinator, Derek Vanek, "When performed properly, selective plating produces an atomic bond between the plating material and the base material equivalent to the cohesive strength of the base material itself. And very often, a plating repair will produce a component that has better performance characteristics - and is more durable - than the original component." This claim is supported by experiences Mr. Feher has had using the Sifco Process over the past 15 years. Says Mr. Feher, "We plated 0.030[inches] thickness of 2085 nickel on some gear reducer shafts that had seal grooves worn into them. Then we machined the shafts to size. The end result was a shaft with a 54 Rc hardness that lasted considerably longer than the original shaft."

Small touch-up systems apply flash deposits on areas as small as 0.003[inches] by 0.0015[inches]. Larger systems use power packs up to 500-ampere output that produce high-quality deposits of up to 0.030[inches] thick in one layer on large areas. Regardless of size or sophistication of the system, all selective plating works in the same fundamental way.

A specially formulated solution is applied to a selected area of the workpiece by a porous, absorbent cover wrapped over the anode of the plating tool. A portable power pack provides direct current. One power pack lead is connected to the plating tool and another is connected to the workpiece. A direct current circuit is completed when the operator places the plating tool on the workpiece. To ensure that a sound, adherent, and uniform deposit is applied, the operator keeps the tool in motion while it touches the workpiece - hence the name "brush plating." Usually, the operator must prepare the base material prior to actual plating. These preparatory steps vary based upon the base material and ensure an adherent deposit.

Over 100 pure metals and alloys are available for selective plating applications that run the gamut from circuit board repair to decorative plating of church steeples. The same equipment and basic techniques are used for specialized applications such as anodizing, black optical coating, and electropolishing.

Today, four of Feher Machine's people are qualified to perform selective plating using any of their three Sifco systems. Mr. Feher has packed his 30-ampere system as carry-on baggage, traveling to a dozen countries to perform various plating repairs. He arranges for Sifco to ship required supplies to his destinations.

Many machine shops equipped with selective plating systems find them useful for keeping their own equipment running as well. One Sifco customer recently repaired worn carrier bores on several multi-spindle screw machines by plating the bores with nickel deposits that ranged from a couple ten thousandths of an inch to several thousandths of an inch thick. Tear-down time was limited to only that required to access the bores.

Says Sifco's Mr. Vanek, "Many machine shops find they can justify the investment in a system based purely on internal applications. But, once they've achieved proficiency - which doesn't take long - they find they have a tool they can add to their repertoire of services and improve their profitability."

Mr. Feher agrees. Even though his customer's situation 15 years ago was a tough problem, it turned out to be a dark cloud with silver plating.