The experimental results show that the effect obtained with zinc double dip process is better than that obtained with zinc single dip process. Through orthogonal experiments optimum zinc dipping technology was established: NaOH 210 g/L, ZnO 20 g/L, NaKC4H4O6·4H2O 40 g/L,dipping time 45 s, solution temperature 20℃.
The principles of hot dip galvanizing protection are briefly explained. Factors influencing the thickness of the coating,anticorrosion properties of the alloy layers and the zinc consumption are discussed.
A kind of zinc-immersion solution with middle nickel and iron ions content was prepared,the optimal zinc-immersion scheme was obtained with orthogonal experiments,and the optimal formula of pre-plating with alkaline electroless nickel was obtained as follows: 25g/L nickel sulfate,25 g/L sodium hypophosphite,30 g/L sodium citrate,10 g/L sodium pyrophosphate,10~15 mL/L triethanolamine,30 g/L ammonium chloride.
Zinc-immersion coating of AZ91 magnesium alloy and its coloring process were investigated by chemical and anodic oxidation method, and the mechanism of zinc-immersion reaction was discussed. Results showed that uni-form and compact zinc coating and coloring zinc coating were obtained on the surface of AZ91 magnesium alloy and zinc-immersion reaction was proved by thermodynamics.
By using brass-strike coating to increase the potential and the properties of zinc-nickel coating with high anti-corrosion and the zinc coating acting as anodic protection,the model,with zinc-immersion as under coatings,provides corrosion protection to magnesium alloy. The corrosion process can be controlled in the interface of coatings between brass and zinc-nickel.
In this paper, the adhesiveness and the corrosion resistance of hot dip Zn 0.1Ni alloy coating are studied by the bending test and the salt spray test and are compared with those of hot dip zinc coating.