Corrosion and Corrosive Wear of Steel for Automotive Exhaust Application 2019-28-0178
In the current scenario, durable exhaust system design, development and manufacturing are mandatory for the vehicle to be competitive and challenging in the automotive market. Material selection for the exhaust system plays a major role due to the increased warranty requirements and regulatory compliances. The materials used in the automotive exhaust application are cast iron, stainless steel, mild steel. The materials of the exhaust systems should be heat resistant, wear and corrosion resistant. Stainless steel is the most commonly used material in the automotive exhaust system. Due to increasing cost of nickel and some other alloying elements, there is a need to replace the stainless steel with EN 8 steel. Recent trends are towards light weight concepts, cost reduction and better performance. In order to reduce the cost and to achieve better wear and corrosion resistance, the surface of the EN 8 steel is modified with coatings. This work focuses on the evaluation of corrosion and corrosive wear resistance of hard chrome plating (HCP), hot dip aluminized coatings (HDA), spray aluminized coatings (SA), electroless nickel coatings (EN) on EN 8 medium carbon steel. Laboratory tests were performed on coated exhaust materials to determine their ranking. The microstructure and microhardness of various coated surfaces were studied. The corrosion studies of the various coated samples were carried out in salt spray apparatus. Corrosive wear studies of the coated samples were carried out in Pin on disc wear testing machine under lubricated conditions. From the results, it was found that the electroless nickel coatings found to be more corrosion resistant which make it suitable for the automotive exhaust application.