Electroplating

The wear resistance of a metal part can be improved by electroplating a harder metal on its surface. The metals most often plated on base material are chromium, nickel and rhodium. Indium plating has been utilized to decrease wear of lead bearings.

Two types of chromium platings used in industry are called as hard chromium & porous chromium. The hard-chromium plate is the simialr as that utilized for decorative purposes however much thicker, generally from 0.0025 mm to 0.25 mm. Porous chromium plating has on its surface carefully controlled pits or channels to hold lubricants. The hardness of chromium plate is equal to 950 to 1050 VHN. Another factor contributing into plating is used in the cylinders and piston rings of internal combustion engines. The high corrosion resistance of chromium is helpful in decreasing wear under corrosive conditions.

The hardness of nickel plating is from 140 to 425 VHN depending upon the nickel plating solution used. Nickel plating is good deal softer than chromium plating; however in many cases it is hard enough for the purpose of and more economical. The better throwing power of nickel plating solutions as compared with chromium plating solutions is an advantage in plating parts that have recesses.

The hardness of rhodium plating is from 540 to 640 VHN and its wear resistance is among those of chromium and nickel plating. Rhodium plating has high heat resistance, high reflectivity, and non-tarnishing properties along with good hardness & wear resistance. Rhodium plated parts are utilized as reflectors of high intensity light sources, for electrical contacts and for slip rings and commutators.