The mechanism of corrosion of cadmium-silver-copper bearing alloys

Abstract

Tests were made at the Lubrication Laboratory at Virginia Polytechnic Institute to determine the mechanism of corrosion of Cadmium-Silver-Copper bearing metals, and if possible to develop a procedure to quantitatively rate oils and inhibitors with respect to corrosion.

Two pieces of testing apparatus were employed - a jet-type oil bath and a glass apparatus. It was found that corrosion of the cadmium base bearing metals took place in the jet-type oil bath with jet velocities equal to 1.51 feet per second at temperatures of 300 and 325° F with Esso Motor Oil, No. 3. Corrosion did not take place at temperatures of 300 and 325° F in the jet-type oil bath when the jet velocities were decreased to 0.67 feet per second.

Tests on the glass apparatus indicated that the corrosion was not electrolytic, that the presence of air (oxygen) at the oil-bearing interface was necessary for corrosion to proceed, and that the scrubbing action of the oil past the bearing face only partially influences the rate of corrosion.

The jet-type apparatus is believed to be quantitative in its results if the surface condition of the bearing specimens and the velocity of the issuing oil jets are accurately controlled.

Viscosity of the oil prior to and after the test was measured. No consistent trend of viscosity was noted, but a tendency for the viscosity of the oil to be directly proportional to the total weight of metal lost by corrosion was pointed out.