Desenvolvimento e aplicação de metodologia de desgaste controlado de aço galvanizado para ensaios de corrosão atmosférica em campo

Abstract

This dissertation shows the development and application of an innovative methodology for controlled wear of galvanized steel, aiming field atmospheric corrosion tests. Galvanized sample preparation generated three different groups according to different carbon steel surface treatment: dry steel grit blasting (group G), dry glass bead blasting (group V) and mill scale acid pickling (group C). The experimental approach used design of experiments (DoE) to decide wear methodology. Preliminary assays were performed to determine initial evaluation parameters, getting to two viable wear types: chemical and physical. Tested variables were solution concentration and immersion time for chemical wear, and flap disc grit and contact time of flap disc with sample surface for physical wear. Screenings and optimization assays were based on full factorial design of experiment (𝑛𝑘) with triplicate at the central point. The aimed goal was 50% reduction of the original galvanized layer, relating this value to mass variation according to each kind of wear. Galvanized compliance tests were performed, as well as electrochemical techniques to evaluate worn surfaces compared to non-worn surfaces. Results indicated that the optimized chemical wear was the most promising, validated with 95% accuracy. Complementary assays allowed a better understanding of the surface wear techniques used. The first data for corrosion rate indicated the possibility to create better predictive models for atmospheric corrosion aiming the electric sector. This work contributes to establish better benchmarks for preventive maintenance, as well as more accurate analysis of extending the service life of galvanized metal structures.