Electrolytic production of Zn-Al2O3 composite coatings was tried in sulfate solutions containing Zn2+ and Al3+ ions by codepositing Al3+-compound formed due to pH rise in the cathode layer. The results obtained are as follows:
(1) The Zn-Al oxide composite was obtained under the conditions that hydrogen evolution was significantly accelerated by the suppression of Zn deposition. Addition of stearyle benzyl ammonium chloride (C-18 benzyl) to the baths was effective for an increase in Al content in the deposit and Al was codeposited in trivalent state in the deposits;
(2) The partial polarization curves of Zn were shifted to the less positive direction due to the suppressed rate of Zn deposition by additive C-18 benzyl
(3) X-ray diffraction patterns of the deposited composites showed that the Al3+-compound that existed in the deposits was θ-Al2O3
(4) TEM observation revealed that the codeposited Al2O3 with a small size of 10 to 100nm was homogeneously dispersed in the deposits.
