Corrosion Resistance and Tribological Behavior of PACVD Coated and Gas Nitrided Surfaces as Alternative to Hard Chromium for Piston Rod Coatings

Chromium layers applied by electroplating processes are widely used as coatings for piston rods in the hydraulics industry for improved wear resistance and corrosion resistance. Despite its advantages of beneficial tribological properties, availability, and established application, there are some drawbacks when using chromium plating, such as the well-known health hazards of Cr-VI precursors. Additionally, because of the introduction of mandatory registration of Cr-VI compounds according to REACH, including CrO3 and chromic acid, the plating industry has to deal with increased organizational expenses. We report on the usage of PACVD and heat treatment methods as potential alternatives for plated chromium as piston rod coatings. A comprehensive characterization of chromium coated and alternatively treated piston rod samples regarding corrosion resistance and tribological behavior showed that heat treated and DLC coated surfaces fulfill the requirements to piston rod coatings for certain application areas and can serve as a promising chromium-free alternatives.