I spent too long debating how best to deal with the harp frame and tone bars. These internal steel parts were originally zinc plated and most have not held up well to the passage of time. Zinc protects the steel by being a ‘sacrificial metal’. Instead of preventing corrosion, the zinc simply corrodes preferentially to the underlying steel. When the zinc corrodes, a white powdery substance is left behind in its place. Although even this powdery oxidation still provides some protection, once the zinc has been converted, the steel is largely left to the mercy of the elements and soon begins to rust and pit.
My debate over these parts centered on whether or not I was going to outsource their restoration. There are a few sources for home electroplating kits and I gave very serious consideration to the product offered by Caswell Inc. which promised everything I’d need to go from bare metal to a professional-quality finish. This appealed to me for a couple of reasons. Ideally, I’d like to perform as much of the pianos’ restoration work as possible myself. Also, the plating kit would likely pay for itself after just a few pianos by saving the cost of using a third party for this service.
Ultimately, I was scared off from the home plating option by the apparent complexity and scope of the job. Even as a kit designed for amateur use, this is no simple operation. It involves multiple stages each requiring its own combination of potentially dangerous chemicals, tricky operating procedures and some degree of luck. The steep learning curve aside, a plating setup – especially one that could accommodate the large harp frames – would occupy a significant amount of real estate in my small shop.
Among the plating businesses I looked at, it seemed standard to divide plating jobs into two general groups: drum and rack. Smaller parts (up to maybe twelve inches long) can be plated using a drum that rotates like a rock polisher. The parts tumble around inside until eventually all surfaces are consistently finished. Larger pieces must be hung from a rack and dipped individually in the plating bath. For my parts, I needed to find a plater that could provide both drum and rack services.
Prior to sending the parts away, they needed to be cleaned and polished. Zinc plating is extremely thin and does nothing to compensate for imperfections in the surface of the base metal. I tried using a blast cabinet to prepare the parts but even using a fine blasting medium, the result was a satin finish that was too far from the original look. Instead, the bulk of the cleaning was done with wire wheels, both on the bench grinder and chucked into a hand drill. After achieving an acceptable finish with a wheel, a final polishing was done with some 400 grit polishing papers.
In the old days, after applying zinc plating, parts would often go through a ‘chromate conversion‘ process that added a protective layer to the zinc. This is what gave the Rhodes parts their iridescent yellow coloring. Although you can still have zinc chromate plating done, it’s more recently been heavily regulated due to reasons discussed in the movie Erin Brokovich. Replacements for the chromate process have been developed but they offer little or none of the protection provided by the old, more toxic process. Although the plater I used offered the old stuff, I chose to go with his replacement option. The resulting color looks pretty good but, at least on the tone bars, could not stand up to even the slightest abrasion.