The purpose of explosion-proof hex keys: They are specifically designed for tightening or removing round nuts on machine tools, vehicles, and mechanical equipment. After being shaped, the explosion-proof hex keys undergo high-temperature bluing treatment. In a solution with a high content of sodium hydroxide and sodium nitrite, at a temperature above 140 degrees Celsius, a dense oxide film (Fe2O3 and ...) is formed on the surface of the steel parts.