Can iron be boiled black at high temperature?

High temperature blackening technology of steel is a common chemical surface treatment method. The principle is to produce an oxide film on the metal surface to isolate the air and achieve the purpose of rust prevention. In the case of low appearance requirements, it can be blackened, and the surface of steel parts is blackened, which is also called bluing. There are two common methods for blackening treatment: traditional alkaline heating blackening and later room temperature blackening.

Alkaline blackening at high temperature is to treat steel parts in alkaline solution containing oxidant at 135℃- 150℃. The technological formula and conditions are: sodium hydroxide: 550-650g/L; Sodium nitrite:150-250g/L; Temperature 135℃- 145℃, time 40-60 minutes, pH 8- 14.

Process flow: solvent degreasing → chemical degreasing → hot water washing → cold water washing → acid washing → cold water washing → blackening treatment → hot water washing.

→ hot water washing → sealing treatment → hot water washing → drying → oil immersion → inspection.