Carbon footprint of the hot-dip galvanisation process using a life cycle assessment approach

This work presents the carbon footprint (CF) of two hot-dip galvanisation (HDG) installations located in Spain with differences in the galvanising capacity and in the manufacturing process. The study determines the influence of the direct emissions (scope 1), emissions from electricity production (scope 2), and indirect emissions from upstream and downstream processes (scope 3). The results showed that steel and primary zinc production were the principal contributors to the CF. So, efforts should be focused on reducing the impact of the raw material production included in scope 3. Furthermore, two sensitivity analyses are presented: i) the production of one kg of two types of zinc products, special high-grade and redistilled zinc; ii) the use of two coatings: zinc for galvanisation and paint for pre-printed steel. The environmental impacts in SHG zinc were higher than in redistilled zinc, for all the impact categories due to the great influence of heavy metals emission. The results for zinc and paint protections showed that under the same level of corrosion, a greater thickness of paint is needed to protect steel pieces, compared to zinc coating. This sustainability assessment of the HDG industry recommends the sought of technology alternatives aimed at resource efficiency, such as zinc recovery from spent pickling baths, that could provide the desirable reduction of the environmental impacts associated to primary resource usage and waste treatment.