A great plater can do a terrible job on a bike frame unless he has taken the time and made the investments necessary to address the unique challenges race frames present. Unfortunately we’have seen many real disasters when platers not specialized in racing frames are involved. Such as:
Stripping old chrome involved use of strong acids and salts, which can excessively remove brazing material. We have seen frames virtually disassembled or by over stripping!
The “hole” story:
Fork blades, seat stays and top tubes which often have small vent or worse no obvious holes but invisible gaps in brazing, that can allow the charge solutions to be “drawn” inside and trapped. We have seen frames with this problem rust out within months. It is critical that all areas in which solutions can enter have two holes of about 3/32”. Most fork blades and seat stays have a single hole to allow exit of hot air during brazing. Filling such holes is unreliable, because charged plating solutions will penetrate gaps only microns in size. If a seal is achieved, it can be opened during polishing. If a leak is detected after plating, two holes must then be drilled through the new plating. For this reason we often drill a second set of holes in fork blades and seat stays prior to plating. Certainly beats rust holes!
Chrome plating does not cover all immersed parts equally. The electric field is weak in enclosed areas (like the seat stay and chain stay joints) and strong at sharp edges (outer lug edges). Thus plating can be too thin in the weak field areas and poorly prepared sharp edges can have chrome buildup. This can all require a lot of polishing, manipulation of electrodes and finesse for a good job. Many older frames, for example, show surface rust at the thinly plated chainstay and seatstay areas. Placement of additional anodes and other techniques are required to “throw” plating in difficult areas, something few shops will attempt.
A real “drag”:
Platers must be concerned about “dragging” solutions, that is, carrying them from one tank into the next. A few parts per million of such contamination can both render a 500 gallon tank to useless toxic waste and in the case of a rinse tank, cause toxins to discharge to the sewer system and cost potentially mean a large fine or closure by regulators.
Re-plated frames are usually rust pitted and require careful and thorough polishing. Lugs and braze-ons are mild steel, tubing is much harder, many platers lack the tools and experience to polish thoroughly without eroding the edges of these parts. Improper polishing can even thin the tubing walls or distort the frame alignment, compromising frame integrity.
“Less is more”:
If one is plating a frame which will be painted except for head lugs and dropouts for example, there is no advantage to plating the entire frame. It is easy to immerse the whole frame, but we minimize the plating on the frame by suspending it only partially immersed. This reduces unnecessary weight and increases paint adhesion. We have seen platers attempt to accomplish this by masking which creates a terrible ridge at the edge the mask that must be ground down prior to painting. What were they thinking??
“Does not count if is does not stick”:
For optimum adhesion of the chrome to steel, tanks chemistry and electrical contacts must be precisely maintained. I may be that adhesion acceptable for many applications is not sufficient for bicycles, where chrome sees severe abuse by quick releases. Quite often, when working with other’s chrome, chrome will peel during the pre-paint blast or worse, when we remove the masking after paint!