This lnternational Standard specifies standard pro- cedures and requirements for the detection and classi-fication of localized overheating on ground surfaces by chemical etch methods. Some methods which have been used in the past are on longer recommended. Specifications should be changed to use the methods in this Lnternational Standard. These etching methods are more sensitive to changes in surface hardness than most hardness testing methods. This International Standard applies to steel parts such as gears, shafts,splines and bearings, but is not appli- cable to nitrided parts and stainless steels