Chromium electroplating

Electroplating. Chromium is electroplated onto various substrates in order to realize a more decorative and corrosion- or wear-resistant surface (24—32). About 80% of the chromium employed in metal treatment is used for chromium plating over 50% is for decorative chromium plating (see Metal surface treatments). Hard chromium plating differs from decorative plating mostiy in terms of thickness. Hard chromium plate may be 10 to several 100 p.m thick, whereas the chromium layers in a decorative plate may be as thin as 0.25 p.m, which corresponds to about two grams Cr per square meter of surface. 

Metal Finishing and Corrosion Control. The exceptional corrosion protection provided by electroplated chromium and the protective film created by applying chromium surface conversion techniques to many active metals, has made chromium compounds valuable to the metal finishing industry. Cr(VI) compounds have dominated the formulas employed for electroplating (qv) and surface conversion, but the use of Cr(III) compounds is growing in both areas because of the health and safety problems associated with hexavalent chromium and the low toxicity of trivalent chromium (see... 

Electroplatings of Chromium. Until the middle to late 1970s, all of the commercially electroplated chromium was produced from plating... 

The non-ferrous alloys include the misleadingly named nickel silver (or German silver) which contains 10-30% Ni, 55-65% Cu and the rest Zn when electroplated with silver (electroplated nickel silver) it is familiar as EPNS tableware. Monel (68% Ni, 32% Cu, traces of Mn and Fe) is used in apparatus for handling corrosive materials such as F2 cupro-nickels (up to 80% Cu) are used for silver coinage Nichrome (60% Ni, 40% Cr), which has a very small temperature coefficient of electrical resistance, and Invar, which has a very small coefficient of expansion are other well-known Ni alloys. Electroplated nickel is an ideal undercoat for electroplated chromium, and smaller amounts of nickel are used as catalysts in the hydrogenation of unsaturated vegetable oils and in storage batteries such as the Ni/Fe batteries. 

Hexavalent chromium-bearing wastewater is produced in chromium electroplating, chromium conversion coating, etching with chromic acid, and in metal-finishing operations carried out on chromium as the base material. 

Plating It On Electroplating chromium onto this 1936 Packard hood ornament, both for beauty and protection against corrosion, requires energy. The other face of. electrochemistry is represented by batteries, which supply energy. This chapter will reveal both faces. 

Comment For the sake of introducing Faraday s law, the details of the electroplating process have been simplified here. Actually, electroplating chromium is only 30% to 40% efficient and must be run at a particular temperature range for the plate to appear bright. Nearly 10,000 metric tons (2X10 mol) of chromium is used annually for electroplating. 

Figure 13. Wear comparison of APS chromium oxide coatings and electroplated chromium sliding against grey iron liners at 200 and 35QPC, lubricated with fresh CE/SF 15W40 oil.

Unlubricated tests again showed very low wear rates for the HVOF WC-Co, although the grey iron liner material was severely abraded due to coating fracture (Figure 19). The Armacor M material showed much better wear properties in comparison to electroplated chromium... 

It is desired to electroplate chromium (Cr) onto a ferritic-martensitic carbon steel automobile bumper for an attractive appearance and corrosion resistance. An electroplating ceU is operated at 7 = 6.68 A and 25 °C. The... 

Cr+ cations are reduced on the bumper (cathode) to form a thin trim of 1.5 nm thick. How long will it take to produce a 1.5 pm thick electroplated chromium film on the bumper if the total surface area is 100 cm and e = 60% [Solution t s= 100 sec.]. 

A commercial chromium coated ring, CKS-36 (supplied by AE Goetze) was also tested. The CKS-36 comprises a multilayer electroplated chromium coating in which alumina particles are embedded [8]. 

In some cases an additive may be added to the final rinse. For instance, a flash rust inhibitor may be added when cleaning steel. Acetic acid may be added to remove the stain on electroplated chromium when chromium is used as a basecoat. 

Chromium, hexavalent (electroplating) Chromium with a plus six charge. Very destructive to sewage disposal plants by killing bacteria. 

Chromium, trivalent (electroplating) Chromium ions with a plus three charge. 

Sublimation source (vaporization) A vaporization source for heating materials, such as chromium, that sublime rather than evaporate. The subUmation source can function best by ensuring good thermal contact between the heater and the solid. Examples Electroplated chromium on a tungsten heater heating by radiation in an oven-like structure direct e-beam heating of the surface of a solid. 

---