Improving Sigma Level of Galvanization Process by Zinc Over-Coating Reduction Using an Integrated Six Sigma and Design-of-Experiments Approach

The hot-dip batch galvanization (HDBG) process is one of the most popular and widely used techniques of galvanization and a prime consumer of 50% of zinc produced annually. An increase in production expenses due to excess zinc and energy consumption is a major problem in the HDBG process of many galvanizing industries. To identify the root cause of zinc and energy consumption and improve the process, a case study is presented in the HDBG process of an Indian tower parts manufacturing industry. Six Sigma’s DMAIC approach is implemented in the HDBG process of this industry and investigated that the over-coating of zinc layer is the major cause of excess zinc and energy exploitation. The 23 factorial model of the design-of-experiments (DOE) is adopted in the improve phase of DMAIC, which established the relation between coating thickness and its influencing factors. The ANOVA confirmed that immersion time and silicon present in tower parts material significantly impact the coating thickness. The immersion time of 3 min has been determined to result in optimum coating thickness. By setting immersion time up to a standard level, an improvement in the HDBG process has been achieved. Due to this, the process sigma level is improved from 0.75 to 3, and now 99.73% of products are within the acceptable range of coating thickness. These outcomes have proven that the Six Sigma implementation together with DOE enhances the product quality and improves the process, which helps industry to achieve sustainable competitive benefits.