ABSTRACT
Surface finish has a relatively small influence on the static tensile strength of a material; however, its effect on the material's endurance limit and its corrosion resistance is very significant. It would seem then that if a diaphragm's Performance is to be improved to its fullest extent, then its surface should be treated with great care. The diaphragm's finish should be specified according to its function, stress level, and most economical methods of surface finish. It must be emphasized that the maximum bending stresses in a diaphragm are developed at the surface, and it is for this reason that the surface layer be comparatively smooth. Metallic coatings such as chromium, nickel, and cadmium should never be used on diaphragms. Fine cracks in the plated coating, internal residual stress in the plating, and hydrogen embrittlement of the base metal are recognized as contributing factors.
