The investigation of organic catalyst and current density effect ob electrolytic chromium coating

Electrolytic chromium coating is widely used in industrial applications due to its high hardness and superior properties such as wear resistance, low friction coefficient, high melting temperature, and good corrosion resistance. In addition to having these attractive properties, the properties of chromium coating are very sensitive to bath composition, coating equipment, and coating parameters. This makes it necessary to optimize each parameter in order to obtain a coating with the desired properties. In this thesis, four different kinds of chromium plating process were applied on St37 steel depending on current density and organic catalyst addition. The coated samples were compared as to surface morphology, corrosion properties, wear and adhesion resistance, hardness, and phase structure. In addition, the effects of organic catalyst addition on pit deffect formation, one of the problems frequently encountered in industrial chrome plating processes, were also investigated. As a result of the increased current density and the addition of organic catalyst, a harder, with higher resistance to abrasion and scratching coating was obtained with the increase in coating thickness. However, the increased coating thickness had an increasing effect on the formation of micro cracks and the corrosion resistance was affected negatively. On the other hand, it has been observed that the addition of organic catalyst has a mechanism to increase pit defect formation. At the end of the study, it was concluded that a strict optimization of the coating bath and equipment properties was required in order to obtain the expected properties from the coating and that changing each parameter had an improving effect on some properties while negatively affecting other properties.