The adhesion of metals and factors that influence it

Abstract Two modifications of the twist-compression bonding method for adhesion testing are described. They are the 180-degree method and the torquemeter method. A study of adhesion vs. friction coefficients is reported. The results obtained, using the torquemeter method, show that high friction between metals is usually accompanied by large adhesion, thus fully supporting the adhesion theory of friction. The effects are illustrated on face-centered cubic metals. The coefficients of adhesion are correlated with hardness and melting points for a variety of metals of different crystal structures. The adhesion properties of rare earth and related elements are treated in some detail, including the results on the adhesion of these elements to iron. Two aspects of adhesion are considered in the discussion of factors that influence it, namely mechanical, and physico-chemical. The mechanical aspect is related to the properties of metals (and their oxides) which affect the size and cleanliness of real areas of contact between two metal specimens subjected to the action of normal and tangential forces. The physico-chemical aspect of adhesion, in turn, involves properties that determine whether adhesion will or will not take place under given experimental conditions.