The Impact of Al Addition to a Zn-AI Bath upon Growth Kinetics and Structure of Coatings Obtained in the Batch Double Hot Dip Process

摘要

In the paper the results of tests on obtaining coatings by use of double hot dip in Zn-Al baths with various Al contents are presented. The coatings were produced in ZnAl baths with the following Al contents: 7, 15, 23, 31 wt. %. Al. Based on Zn-AI alloy solidification curves the optimum temperature of the metallization process has been determined. The growth kinetics has been defined and the structure of coatings has been developed. It has been established that an increase in Al contents to 23 and 31 wt. % in the bath leads to excessive growth of the coating thickness and its porosity. Smaller contents of Al (7 and 15 wt. %) in the bath allow to obtain coatings of a favourable structure and correct thickness.