Boundary Film Formation by ZnDTPs and Detergents Using ECR

Abstract

Overbased detergents and ZnDTPs form insulating boundary lubrication films. Electrical contact resistance (ECR) is therefore a convenient method of monitoring boundary film changes in a sliding contact. Separately, ZnDTPs and overbased detergents rapidly form insulating films. In combination, however, films may form slowly and, furthermore, may be less stable than films formed by the individual additives. Examples of film formation by ZnDTP-detergent combinations are described. ECR provides no information on boundary film chemistry. X-ray photoelectron spectroscopy (XPS) has been used to help identify some of the films. Inferences as to the chemistry of film formation can be drawn in some cases.