A chromium-free water based coating for treating a galvannealed or galvanized steel surface

A chromium free water based coating is developed for treating Galvannealed or galvanized steel surface. The coating is based upon hybrid condensation product of water soluble sol-gel solution prepared from solution containing one or more organofunctional silanes. The said silane solution is hydrolised at pH 4-6.5 for 16 hours at room temperature with continuous stirring at a speed of 300-800 rpm. The coating composition when applied on a galvanized and galvannealed steel substrate provides more than 200 hours of white rust resistance at a coating thickness of less than 5 micron and can dry within 10-30 sec at 80-90 DEG C peak metal temperature. 为处理镀锌层退火或镀锌的钢表面发展的无铬水基涂料。该涂层基于从含有一种或多种有机官能硅烷制备的水溶性溶胶-凝胶溶液的混合缩合产物。将所述硅烷溶液在pH 4-6.5下在室温下水解，伴随以300-800rpm的速度连续搅拌16小时。当施加于镀锌及镀锌层退火的钢基材上时，该涂料组合物在小于5微米的涂层厚度下提供了超过200小时的白锈抵抗性，并且可以在80-90摄氏度的峰值金属温度下在10-30秒内干燥。