Iron oxides and rust (hydrated iron oxides) in tribology. D. Godfrey. Lubric. Engng., February 1999, 55(2), 33--37.
Five samples of anhydrous iron oxides and ten hydrated iron oxides, which are described as rusts, are evaluated in tribological studies. Typical properties of the fifteen test materials are tabulated. The main properties of interest are composition, formula, crystal structure, magnetic properties, colour and hardness. Optical micrographs show fretting corrosion of steel/steel surfaces, and scanning electron micrographs show wear marks and pits under a corrosion wear scar and corrosion pits under rust. Field examples of failures are reviewed, Four guidelines are given to enable tribologists to distinguish between hematite from fretting corrosion and hydrated iron oxides from rust. 8 refs.