Re: [CR] Aluminized Steel

(Example: Racing:Jacques Boyer)

Date: Wed, 2 Sep 2009 06:07:35 -0700
From: "verktyg" <verktyg@aol.com>
To: John Hurley <JHurley@jdabrams.com>, <Classicrendezvous@bikelist.org>
References: <249DDD9704676C49AE6169AE3D2D9F4ECDB883@Exchange-SVR>
In-Reply-To: <249DDD9704676C49AE6169AE3D2D9F4ECDB883@Exchange-SVR>
Subject: Re: [CR] Aluminized Steel


John,

Most decorative chrome plating consists of 2 or 3 layers. In the best quality chrome plating the base metal is first polished then a layer of copper plating is applied. The copper fills in a lot of the scratches and defects. It's very soft and polishes well, leaving a smooth finish after plating. The copper base layer is eliminated for less expensive chrome plating applications.

The next step consists of one or two layers of nickel plating which is harder than the copper. The nickel coating is also polished when a bright finish is required. The final layer is a very thin coating of chrome plating as little as 10µm thick on top of the nickel.

The plating on Simplex LJ series front dérailleur cages can be bright polished or satin finished chrome. The satin finish chrome plating, is achieved by sandblasting or acid etching the base metal or nickel layer before chrome plating to produce a uniform matte or satin finish. The finer the grit of the sandblasting media, the smoother the finish.

The steel portions of many dérailleurs are zinc or cadmium plated instead of chrome plated. The problem with zinc plating is that it quickly turns dull.

I always suspected that the cages on some early SunTour front dérailleurs were aluminized. Aluminizing or aluminum plating isn't practical on components like dérailleurs because it can be easily scratched which would allow the steel underneath to corrode.

Chas. Colerich Oakland, CA USA

John Hurley wrote:

Does anyone know if some of our favorite classic bike bits were made of aluminized steel? I'm thinking about the derailleur cages of certain Simplex front derailleurs. It's steel, but without either the shine of chrome or the flat look of zinc. It has a nice, even, buffed-looking finish, sometimes called a matte finish, I think. I don't know if aluminizing of steel is done with a hot-dip or electro-plating process, but it does give a nice durable finish. I've often wondered how certain steel items are protected if they aren't stainless, chromed or galvanized. Saddle rails and spokes come to mind. Zinc is effective, of course, but can be pretty dingy-looking. Maybe some of you amateur (or professional) metallurgist-types can comment.

John Hurley
Austin, Texas, USA