Life-cycle assessment as a tool to evaluate the environmental impact of hot-dip galvanisation

Abstract

Hot-dip galvanisation (HDG) is the method most commonly used to protect steel surfaces from corrosion. However, HDG involves very intensive consumption of energy and resources. This paper aims to evaluate the environmental performance and hotspots in the Spanish HDG sector using cradle-to-gate life cycle assessment (LCA). Two Spanish HDG industrial plants, with different galvanisation capacities and manufacturing processes, were selected for the case study. The LCA revealed that the consumption of energy, fuels and nonrenewable resources were the most relevant environmental burdens at both plants. Steel was the main contributor, as it had the greatest influence on the plants? environmental profiles. The consumption of primary zinc and natural gas, used to dry and heat the molten zinc bath, also contributed to the impact of the HDG plants. This work proposes a normalisation to compare the Spanish sector against a European reference based on the average of 66 companies in 14 countries. The impacts of the Spanish HDG plants being studied were generally below the EGGA values, although the results are strongly influenced by the type of steel and the degree of material reuse implemented in the steel manufacturing process. The study lays the foundations for improvements in the resource efficiency and productivity of galvanisation plants. We propose alternatives such as the use of secondary zinc or modifications that will extend the lifespan of pickling baths, which would contribute to a more sustainable use of resources in the galvanising industry.