Corrosion resistance evaluation of boron-carbon coating on ASTM A-36 steel

The ASTM A-36 steel is the main material used in the manufacture of products and parts for general construction and mechanical engineering purposes. In this work, the effect of boron-carbon coating on corrosion resistance and hardness of the steel ASTM A-36 is reported. A boriding thermochemical treatment was performed at 950 degrees C during 4 h. Followed by, a carburizing process for 6 h at 930 degrees C. The corrosion analysis was done by electrochemical impedance spectroscopy (EIS) polarization and Tafel technique, which employed a fused deposition modeling-based 3D printing electrochemical cell made of polylactic acid (PLA). A commercial platinum foil and a silver/silver chloride (Ag/AgCl) electrode with 3.5 M potassium chloride electrode solution (Electrolyte) were employed as the counter and reference electrode, respectively. and area 1 cm(2) of the sample was employed as the working electrode (WE). Optical microscopic analysis shows that boride phase grown on the treated surfaces has a shark-tooth morphology with a thickness of about 60 mu m in samples. The carburizing over boride layer promotes the conformation of coatings on the outermost layer of the samples with a thickness of about 17 mu m. X-ray diffraction (XRD) spectrum shown only the formation of the iron diboride phase (Fe2B). Results shows that boride samples have inferior corrosion resistance in comparison to virgin sample, but after carburizing, an outer layer is formed, with the hardness and corrosion resistance similar to the original sample.