Offshore oil drilling environments operate under extreme conditions such as high temperature, high pressure, and salinity. Securing mechanical reliability and corrosion resistance of each component is directly linked to overall system stability. The Hwashin Technical Research Institute is developing machining technology for large-diameter (5-1/4 inch) fasteners with strength, ductility, and corrosion resistance for drilling systems. In cooperation with Pukyong National University, multi-layer plating technology is being developed to enhance corrosion resistance in saline environments.