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Trivalent chromium plating, also known as tri-chrome, Cr 3+, and chrome(III) plating, uses chromium sulfate or chromium chloride as the main ingredient. Trivalent chromium plating is an alternative to hexavalent chromium in certain applications and thicknesses (e.g. decorative plating). [3]
Black nickel plating was developed around 1905, and between the two wars, black chrome plating (first German patent 1929.GP 607, 420), which saw wider use only from the mid-1950s. [14] After the First World War, the first procedures for anodic oxidation and coloring of anodically oxidized aluminium were developed (1923, 1924.DRP. 413876).
The latest modern development occurred in the 1980s, with the new generation of alkaline, cyanide-free zinc. Recent European Union directives ( ELV / RoHS / WEEE ) [ 3 ] prohibit automotive, other original equipment manufacturers (OEM) and electrical and electronic equipment manufacturers from using hexavalent chromium (CrVI).
If chromium is plated directly onto the steel, then their different thermal expansion coefficients will cause the chrome plating to peel off the steel. Nickel , Nichrome , tantalum , hafnium , niobium , zirconium , vanadium , and tungsten are a few of the metal combinations used to form diffusion barriers for specific applications.
A #7 finish is produced by polishing with a 280–320 grit belt or wheel and sisal buffing with a cut and color compound. This is a semi-bright finish that will still have some polishing lines but they will be very dull. Carbon steel and iron are commonly polished to a #7 finish before chrome plating.
Class 2 plating, also known as “industrial chromium” or “hard chromium”, is used for wear resistance, abrasion resistance and such incidental corrosion protection of parts as the specified thickness of the plating may afford. Engineering chromium is usually applied directly to the basis metal and is finished by grinding to the specified ...
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Electroplating baths and equipment based on the patents of the Elkingtons were scaled up to accommodate the plating of numerous large-scale objects and for specific manufacturing and engineering applications. The plating industry received a big boost with the advent of the development of electric generators in the late 19th