Metal joining between two pieces of aluminum rods by precision electroforming at room temperature and evaluation of their adhesion strength.

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We made two pieces of aluminum rods (A1070BD-H14) join by precision electroforming at room temperature. The electroforming of zinc or nickel on the contact boundary regions of their aluminum rods was performed after previously mechanical attaching by a bolt. After electroforming and subsequent detaching of the bolt, the adhesion strength between the aluminum and electroplating films was evaluated by tension tests. The oxide film formed spontaneously on aluminum surface caused weak adhesion between electroplating film and aluminum substrate. Therefore, after mechanically abrasion by commercial emery grid paper, for the improvement of their adhesion strength we applied a chemical Al/Zn substitution process using zincates solution to prevent formation of the oxide film. The composition of the zincates solution was 5.0 g/dm^3 ZnO - 120 g/dm^3 NaOH - 2.0 g/dm^3 FeCl_3・6H_2O -50 g/dm^3C_4H_4NaKO_6・4H_2O - 1.0 g/dm^3NaNO_3.As a result, it confirmed that electroforming was an excellent method for joining aluminum metals each other at room temperature. Beside of the chemical surface finishing by the zincates treatment, the mechanical abrasion process also influenced greatly on the adhesion strength between the aluminum and electroplating metal films of zinc or nickel. For example, the strongest adhesion strength was carried out in the following chemical surface finishing process, first zincates process for 90 seconds and then etching process by 36 vol. % HMO_3 for 60 seconds and succeeding 2^<nd> zincates process for 30 seconds. On the other hand, we found that the mechanical abrasion by commercial emery grid paper of #1000 before a similar zincates process always improved greatly their adhesion strengths in tension tests.