Chrome Plating on Bicycle Frames

In 1982 when I began building custom frames in San Marcos, Southern California, I was fortunate that there was an excellent chrome plating business in nearby Escondido.

It was the chrome lug work and other parts of the frame that helped me gain my reputation for beautifully finished work.

This was the same plating shop used by Masi, later used by myself, Dave Tesch, Brian Baylis and other local builders.

What makes a high quality chrome finish is the same as what makes a good paint finish; it is what’s underneath, the preparation.

On a frame like the one pictured above, the whole frame is chrome plated, however, only the parts that will show are polished; the main tubes that are painted are left rough.

First it would be an unnecessary expense to polish these parts, and secondly the rough surface made a better key for the paint.

The parts of the frame that would be left exposed chrome plating were first highly polished. The slightest scratch left by a piece of emery cloth, would show after the plating process.

To achieve the best chrome finish, (Which this is.) the polished steel is first copper plated, polished again, then nickel plated over the copper, and finally chrome plated.

The copper affords the best adhesion to the steel; nickel gives the finish more corrosion resistance, but is yellowish in color. Finally the chrome gives the bright, bluish, almost mirror like finish. The coats of plating are extremely thin, measured in millionths of an inch, rather than thousandths.

Chrome is an abbreviation of the word Chromium, one of 91 natural occurring elements. Chromium is a metal which is not useful by itself; things are not made from chromium. However, it can be alloyed with steel to increase strength and hardness, or used for chrome plating.

Chrome is always applied by electroplating; it is not simply dipped in a tank. Say for example a frame was to have a chrome rear dropout faces, right chainstay, (To prevent chain slap damage.) and a chrome front derailleur braze-on. 

The Fuso Lux frame (Above.) and the John Howard fames were chromed in this fashion.

The frame is suspended in a vat of chromic acid. H2CrO4 with the parts to be plated below the surface, the surface of the liquid acid is agitated to make small waves. Without this there would be a solid line where the plating ends that would show beneath the paint.

Electric terminals are connected to a plating material, either copper, nickel, or chromium and to the frame to be plated. A current passes through the acid solution (Electrolyte.) and molecules of the metal travel through the solution to deposit on the frame.

A frame plated in the manner just described would be plated 2 or 3 inches up the seatstays, to include the whole rear dropouts on both sides, left and right chainstays, and the bottom bracket shell. In addition, the seat tube would be plated up to 2 to 3 inches above the front derailleur braze-on.

Also of course part of the down tube would be plated; it being impossible to immerse the derailleur braze-on without immersing much of the lower portion of the frame.

As I mentioned before, only the dropout faces, right chainstay, and front derailleur braze-on would be polished; the remainder would be plated, but with a rough, less shiny surface.

A frame with chrome head lugs (Picture left.) would have the head tube and several inches of the top and down tube plated.

After chroming in this manner the parts to be left unpainted would be masked with masking tape.

The edge around lug work required some delicate cutting of the tape with an Exacto knife.

If a fork crown was chromed the steering column was masked with duct tape before the fork was placed in the tank so it was not chromed.

Similarly, the bottom bracket threads were protected with a rubber plug.

I would use an etch primer over the chrome; this contains phosphoric acid that etches into the metal and provides a firm key for the coats of paint that followed.

Good chrome plating is expensive; one of the reasons being the high cost of disposing of the large amounts of toxic waste this process generates. Even the water used for rinsing the chrome parts after the plating cannot be disposed of without first treating it to render it harmless.

I remember the shop in Escondido had a low wall, about 18 inches high, built around the plating tanks so any spillage was contained, and could not escape out of the building and seep into the ground.

The chrome plating industry was the first to be regulated for toxic waste by the government, and is still highly regulated. Workers in the industry have to undergo regular medical checkups.

It is not the business I would choose to be in, but I was glad to have access to a good plating shop when I needed it.

Important Footnote.

Throughout the 1980s it was common practice for bicycle stores to tap treads and face the bottom bracket of a new frame before assembly. Also, the head tube was reamed and faced top and bottom. Finally, the seat tube was reamed.

The reason being that most import frames, especially those from Italy, were shipped from the factory with these parts unfinished.

However, all frames from my shop had the bottom bracket threads tapped, and all other necessary reaming and facing was done before the frame was painted. After painting the bottom bracket and head tube faces were carefully sanded to remove excess paint but leaving the primer coat to protect from rust. Threads were re-tapped, and the seat tube reamed, again to remove any paint residue.

Once a frame has been faced in this manner, under normal circumstances it should not need to be refaced. The BB cups and head bearing cups are not moving parts, therefor there should be no wear. This did not stop over-zealous bike mechanics from refacing my frames.

It becomes a serious issue when a bottom bracket and head lugs are chromed, like the frame pictured at the top of this article. To reface such frame will not only ruin the cutting tool, but there is also a danger large chunks of chrome will peel off and ruin the frame.

Never re-face a frame that I built that has chrome, it was faced before it went to the chrome plater. If it has a chrome right chainstay the bottom bracket will be chromed under the paint as mentioned in the above article.

A more detailed description of the Chrome Plating Process can be viewed here

Comments

[edstainless]

I never had a chrome frame back in the day but currently own three bikes from the late 70's that are full chrome. One made in France, one in Japan, and one in the US.
I have seen some electroless Ni plated (NiP) frames that looked great. The chemistry of the bath has a lot to do with the color. And it is much harder than Cr which makes polishing a real pain.

[Keith]

Good one Dave, I’m a fan of chrome on steel frames. Once had an Italian Masi Prestige with a full chrome frame covered with pearl white paint, absolutely stunning.!

There is the appearance aspect which adds a touch of class but full chrome stays and forks are protective as they take much of the scrapes, and dings from flying debris. I’ve found over time they save a lot of touch-ups and a respray if it gets too bad, well worth the extra cost of getting it done.