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Wear and corrosion involve many mechanical and chemical mechanisms, and the combined action of these mechanisms often result in significant mutual reinforcement. Other researchers have studied the interactions of wear and corrosion in a qualitative way for specific wear-corrosion environments. The US Bureau of Mines is interested in presenting the results of wear, corrosion and wear-corrosion tests in a standard format, so that these data can be utilized to develop practical engineering criteria for any tribosystem. To reach this goal, penetration rate equations have been developed to quantify the wear and corrosion processes and wear-corrosion synergism.

A US Bureau of Mines study to quantify synergism between wear and corrosion of white cast iron in an aqueous sulfate environment was conducted using a rotating cylinder-anvil apparatus. A commercial 13.5% Cr white cast iron sample and the individual constituents of a white cast iron were studied to determine the role of each phase in the degradation processes of wear, corrosion and wear-corrosion synergism. These constituent phases consisting of matrix (13%Cr87%Fe), Cr-depleted matrix (5%Cr95%Fe) two M 7 C 3 's and two M 3 C (where MFe,Cr) were fabricated by powder metallurgy. The wearcorrosion studies consisted of four tests: the potentiodynamic polarization tests with and without anvil pressure and wear tests with and without cathodic protection. The force on the anvils was 28 kg and the rotation speed of the approximately 2.5 cm diameter samples was 5.24 (rad s −1 ) with peripheral velocity of 0.0654 m s −1 . Even though corrosion alone was a small percentage of the total degradation, representing as little as 0.1% of the total degradation, the wear-corrosion synergism contribution was significant, accounting for as much as 91% of the total degradation.

Experiments were conducted by US Bureau of Mines researchers with iron-aluminum alloys (5–25wt.%Al) in 1 N H 2 SO 4 to determine the amount of charge required to repassivate their surfaces following scratching with a diamond indenter, to gain a better understanding of how wear and corrosion interact. This understanding is aimed at reducing the corrosion and wear of materials. Solutions saturated with air were used at ambient temperature. Formation of the passive films was studied by measuring the current transient resulting from stepping from the open circuit corrosion potential to the passive region of +1.175 V(NHE). The repassivation kinetics were studied by measuring the current transient caused by scratching a rotating disc electrode with a diamond indenter while holding at the passivation potential. Comparison of the charge density required to form or repair the passive film was made for the potential step and scratching experiments. The amount of charge required to repassivate the film was determined as a function of indenter load, shape, velocity and aluminum content.

A portable slurry wear apparatus, developed by the U.S. Bureau of Mines, was used to study slurry erosion in the laboratory and in situ at a gold ore processing plant. The wear cell of the apparatus was identical with an earlier laboratory model. It used an impeller running at tip speeds of less than 22 m s −1 to drive a continuous flow of fresh slurry past 16 specimens. Laboratory experiments run in an aqueous slurry of silica sand showed that ultrahigh molecular weight polyethylene (UHMWPE) wore less than any metal alloy or other polymers evaluated at 8 or 12 m s −1 , and at 16 m s −1 several polymers wore less than two steels. However, in gold ore slurries from an industrial float cell and rod mill, high chromium white cast irons wore less than UHMWPE at 8 and 12 m s −1 ; and in the rod mill slurry at 16 m s −1 the polymers wore no better than the steels. The same trends were observed previously in an industrial slurry containing a lead-zinc sulfide ore. In all cases the wear rate varied roughly as the fourth power of the impeller tip velocity. When particle shape was held constant, the wear rate always increased with particle size. The effect of particle shape was more complex: angular particles were more detrimental to polymers and rounded ones were more detrimental to alloys. Pitting corrosion also removed material from the alloys. For high chromium white cast irons, corrosion and erosion varied with microstructure.