Brighton Best BR225076 3/8"-5/16-18X2 1/4" Socket Shoulder Screws Coarse Alloy Nylon-Patch Thermal Black Oxide

Black oxide is a conversion coating (similar to Alodine) that is used for steel and stainless steel. It is used mainly for appearance and for mild corrosion resistance. Black oxide impregnated with oil can provide the highest amount of corrosion resistance. Black oxide is formed in a process similar to anodizing, where the parts are dipped into various hot baths of chemicals that convert the surface of the material into magnetite, which creates the black color. Black oxide does not have a significant dimensional impact, therefore masking parts is not necessary. This process can take a longer time due to the manual labor required and the time it takes for the baths to come to the correct temperature.