A novel aluminum alloy surface pretreatment process with fluoride-free and ammonium-free formula was developed. Through the two-step process of pretreatment etching-neutralizing

the aluminum alloy surface was smooth and had excellent sand finishing

the aluminum consumption was less than 2.0%. The sand finishing performance of the new process was better than that in the traditional alkaline-etching process

and was close to the traditional acid-etching process. The aluminum consumption of the new process was reduced by 71% compared with the traditional alkaline-etching process

and was close to the traditional acid-etching process. The process duration was 23% and 31% faster than the traditional alkaline-etching process and traditional acid-etching process

respectively. The optimum composition of the formula was: Na2CO3 (80 g·L-1)

NaOH (8 g·L-1)

Na2SO4 (25 g·L-1)

Na3PO4 (20 g·L-1)

SDS (0.6 g·L-1) and glycerol (5 g·L-1). The process was operated at 55℃ for 10 min. This process achieved following functions in one-step: degreasing

sand-finishing

surface mechanical lines-eliminating. This novel process has the advantages of lower pollution and water consumption

shorter process and higher efficiency

which is environment friendly and energy efficient.