Abstract: Corrosion control cathodic protection for the rod string and the well tubing. Anode assemblies for mounting on the rods of the rod string.

Abstract: A centralizer for a pump rod string which minimizes the resistance offered thereby to flow of well fluids therepast having a body provided with two pairs of longitudinally and circumferentially spaced radially outwardly extending ribs and a circumferential area of reduced external diameter between the two pairs of ribs providing a circumferential line of reduced mechanical strength to minimize likelihood of occurrence of longitudinal cracks in the body of the centralizer and minimizing flaking of the body when the body is subjected to strains and stresses due to bending of the rod, on which it is rigidly mounted, about axes substantially perpendiculer to the longitudinal axis of the rod and also providing flow passages of increased area between the two pairs of ribs.