Chrome , -even Smoke Chrome. But it's all the same stuff, being plated pretty much
the same way it has been since the 1920's. It comes to us in drums, as a red flake.
We dissolve the flakes in water to produce Chromic Acid, and add a bit of Sulfuric
acid to it to make our Chrome plating solution. The part is made the cathode and, with
the passage of a DC current via lead anodes, chromium metal builds on the
component surface.
Hard Chrome plating is the skilled trade of the plating industry. The thickness of the
deposit must be controlled. The solution has very poor electrical characteristics, so
special anodes are often built to get even plating on parts. Each piece must be
fixtured to conduct electricity to the part. And areas of the part that can't be plated must
be kept from both the effects of the acid and the electricity.
For the engineer, some of the attractive properties of hard chrome plating include: It is ultra hard -850-1000Hv (65-70Rc), harder than most industrial abrasives and steel counter faces. Unusually, it combines this hardness with a degree of toughness, so the deposit can stand up to high stress contact. It gives superb substrate adhesion; greater than 10,000 psi.
Before plating, substrates are subjected to rigorous cleaning, so that the surface to be
coated is completely free from contaminants. But the ultimate adhesion factor takes
place in the plating bath itself, with an initial reverse voltage surface etch which actually
dissolves the surface and cleans to a molecular level. It can be applied to a wide
variety of substrates, encompassing a range of steels (including stainless steels and
cast irons), lightweight aluminum alloys or titanium alloys, copper alloys and bronzes,
as well as nickel-based alloys.
Chrome has a bright, attractive finish; it responds well to grinding and polishing,
providing ideal surfaces for dealing with delicate products (like textiles and paper), for
giving low friction, and for high precision parts. The deposition temperature is low; and has little effect on substrate properties. If high strength steels are stress-relieved
sometime before plating and heat-treated again afterwards (usually for a few hours at
about 200 C), there will be no problem with hydrogen embrittlement.
Hard Chrome can be applied to a wide range of geometries. With careful attention to
anode design and jigging, chrome plating can be applied evenly to flat surfaces, to
fine bores, to cylindrical surfaces like shafts or rollers, and to holes and close
tolerance assembly areas. The plating is stable and non-corrodible. It gives ultra
high metal-to-metal sliding wear resistance; up to 100 times less wear than given by
through-hardened, induction hardened, carburized or nitride steels in dry sliding
situations, and greatly superior to electro less nickel. It provides superb abrasion
resistance, even under high contact stresses. It gives a very low wear rate (at least
100 times better than hardened steel or electro less nickel) with abrasive products like
textiles, paper and food stuffs. With thick deposits, it gives excellent wear resistance
under high stress contact against sand, coal, cement, limestone, glass fibers, etc.
With abrasion being the most common and destructive wear process found in industry,
hard chrome has the potential to solve many problems in pumps, valves, bearings,
etc. throughout a wide range of industries; including pharmaceutical, chemical, oil and
gas, textiles, printing, food, mining, and countless others.
Hard chrome does not corrode. It resists abrasion because of its excellent lubricity
properties and significantly extends the product or parts life. Therefore hydraulic
rams, valves, bearings, pumps, cylinders and moving parts found in manufacturing
and production equipment are all potential users of Hard chrome. And yet most
people think we just salvage grinding goof ups!
It might be noted that I have no educational background to be able to verify any of the above statements , but that I did make an effort to only steal material from professional looking websites.
Just Call Chuck
815-389-4700