PURPOSE: To manufacture a galvannealed steel sheet excellent in spot weldability as well as corrosion resistance and adhesive strength of a coating film by forming a mixed film contg. the silicate of alkali metals and colloidal silica on the surface of a steel sheet having a galvannealed layer.
CONSTITUTION: The surface of a steel sheet having a Zn-Fe alloy plated layer having a compsn. contg. 6 to 20wt.% Fe and the balance Zn is coated with a mixed soln. obtd. by mixing the silicate of alkali metals such as sodium silicate, potassium silicate and lithium silicate in the ratio of 3 to 10 and contg. a coupling agent such as a silane coupling agent, which is thereafter dried to form an inorganic film of 0.2 to 5g/m2 coating weight. The galvannealed steel sheet particularly more excellent in spot weldability than conventioned one can be manufactured.
MIKI KENJI
SAKAI HIROHIKO
| JPS5128650A | 1976-03-11 |