Surface compression process for automotive aluminium or aluminium alloy components in a hot mixture of distilled water and alcohol

摘要

In a surface compression process for automotive aluminium or aluminium alloy components, the surface is anode-oxidised to a depth of between 2 and 30 microns. The surface is then hot-compressed in a bath containing a pure or mixed liquid whose boiling point is greater than 100 [deg] C at normal pressure. The hot compression process takes place at above 100 [deg] C. The liquid in the hot bath is distilled water with one or more 20 per cent plus additives e.g. multi-valent alcohols such as diols or triols, e.g. thylene glycol, propylene-glycol, di-ethylene-glycol or tri-ethylene glycol. Prior to the compression stage the material is cold-sealed in a mixture of distilled water and nickel fluoride at a temperature of 25 to 35 [deg] C and pH of 6 to 7 for at least 4 minutes. The compression temperature is in the range 120 to 150 [deg] C, and the pressure is 1 to 6 bar. The material is compressed under these conditions for 20 seconds to 2 minutes.