Aspects of Applying Hard Chromium Coatings on the Inner Surfaces of Components for Hydraulic Drives with Hydrostatic Guideways

We considered the processes of chromium plating the inner surfaces of the components of cylinders with hydrostatic guideways. We demonstrated the various aspects of the chromium plating process – the limitations placed on the machinery depending on the dimensions of the parts to be plated and the unevenness of the deposition rate of chromium along the length of the part. We developed a diagram of an installation for the application of a hard chromium coating on inner surfaces, which includes a cathode, an anode, a tank, and a pipeline. The distinctive features of the installation are the method of supplying the electrolyte at an angle to the horizontal, which allows us to supply the electrolyte through a turbulent flow swirling along a helical path, and the use of a chromium-plated installation casing. We studied various modes for applying a hard chromium coating on the inner surfaces of a hydraulic cylinder. As a result, we determined the optimal composition of the chromium electrolyte – the ratio of chromic anhydride and sulfuric acid – which is 10:1, respectively, and experimentally selected deposition modes. Chromium coatings obtained through the use of the concentrated electrolyte, which we developed, and the chromium plating method have 5...20% greater hardness and a 10...30-times reduction in porosity with the formation of a shiny, lumpy sludge, which corresponds to corrosion-resistant and wear-resistant coatings needed to manufacture hydraulic drives with highly efficient hydrostatic guideways.

Corrosion Rate of Black Chromium Coating Result of Electroplating on Copper

The problem faced is that the white chromium coating has a low selling value or aesthetic value than the black chromium layer which is more in demand, especially by the younger generation who prioritizes aesthetics. The purpose of the corrosion test was to determine the corrosion resistance ability of the black chromium coating resulting from the electroplating process on the relationship between the solution temperature and the immersion time of copper in a corrosive solution. Corrosion test methods include literature studies, field observations, weighing specimens, immersing specimens in corrosive solutions, weighing specimens, calculating corrosion rates, and data analyzing. Corrosion test results show that the higher the temperature of the solution and the longer the immersion time, the smaller the corrosion rate for the lowest conditions at 30oC and a duration of 5 minutes with a corrosion rate of 0.2004 mm/year and the highest conditions at a temperature of 50oC and a duration of 9 minutes at a rate of corrosion of 0.0108 mm/year.