Abstract: It has been found that esters and polyesters of thioglycolic acid, which form a protective, water insoluble complex with zinc atoms, are suitable for inhibiting wet storage staining and the formation of white rust in zinc and zinc coated materials. Many of these compounds are new products.

Abstract: A closed circuit hydraulic control system for an hydraulic motor including a cylinder, a piston movable in such a cylinder, and a rod connected to one side of the piston, such cylinder having a blind end and a rod end through which the rod extends. A reversible circulating pump having two ports is provided for supplying fluid under pressure to the blind end and to the rod end respectively of the cylinder. A first tubing interconnects the blind end of the cylinder to one port of the reversible pump, whereas a second tubing interconnects the rod end of the cylinder to the other port of the reversible circulating pump. Means are provided to accommodate the volume of fluid displaced by the rod as the piston is moved toward the blind end of the cylinder.