Friction and Wear of Iron and Nickel in Sodium Hydroxide Solutions

Abstract

A loaded spherical aluminum oxide rider was made to slide, while in various solutions, on a flat iron or nickel surface reciprocating a distance of one centimeter. Time of experiments was one hour during which the rider passed over the center section of the track 540 times. Coefficients of friction were measured throughout the experiments. Wear was measured by scanning the track with a profilometer. Analysis of some of the wear tracks included use of the SEM (scanning electron microscope) and XPS (x-ray photo-electron microscopy). Investigated were the effects of Various concentrations of NaOH and of water.

On iron, increasing NaOH concentrations above 0.01 N caused the friction and wear to decrease. This decrease is accompanied by a decrease in surface concentration of ferric oxide (Fe₂O₃) while more complex iron-oxygen compounds, not clearly identified, also form. At low concentrations of NaOH, such as 0.01 N, where the friction is high, the wear track is badly torn up and the surface is broken. At high concentration, such as 10 N, where the friction is low, the wear track is smooth. The general conclusion is that NaOH forms a protective, low friction film on iron which is destroyed by wear at low concentrations but remains intact at high concentrations of NaOH.

Nickel behaves differently than iron in that only a little NaOH gives a low coefficient of friction and a surface which, although roughened in the wear track, remains intact. With water alone, the track is torn up and broken although the friction is very little higher than in the NaOH solutions. It may be that it takes less NaOH to form a protective film on nickel than iron.

Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE Lubrication Conference in Washington, D.C., October 5–7, 1982

Notes

Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE Lubrication Conference in Washington, D.C., October 5–7, 1982