BOUNDARY FILM FORMATION BY ZNDTPS AND DETERGENTS USING ECR

Overbased detergents and ZnDTPs form insulating boundary lubrication f ilms. Electrical contact resistance (ECR) is therefore a convenient me thod of monitoring boundary film changes in a sliding contact. Separat ely, ZnDTPs and overbased detergents rapidly fan insulating films. In combination, however, films may fan slowly and, furthermore, may be le ss stable than films formed by the individual additives. Examples of f ilm formation by ZnDTP-detergent combinations are described. ECR provi des no information on boundary film chemistry. X-ray photoelectron spe ctroscopy (XPS) has been wed to help identify some of the films. Infer ences as to the chemistry of film formation can be drawn in some cases .