Impacto da submersão de perfis extrudados de alumínio em soluções alcalinas: um estudo de capabilidade

Abstract

Marcel Pourbaix dedicated himself to the study of metal corrosion, culminating in the publication of the "Atlas of Electrochemical Equilibrium" in 1964. His work presents diagrams that predict the stability of chemical species under various electrolytic cell conditions. The present study utilized this knowledge to corroborate the hypothesis raised by Hydro Aluminum, indicating that the alkaline degreasing bath applied to its extruded tubes impacted the increase in the minimum force required for interference fit crimping, resulting in non-compliance with customer specifications. To solve this problem, a proposal for improvement was initiated, which involved replacing the alkaline degreasing bath with a neutral solution bath. According to Pourbaix, the alkaline environment favors the solubilization of Aluminum oxide (Al2O3) while in a neutral environment, metallic Aluminum (Al) is passivated, ensuring the statistical stability of the process. To monitor this, 180 samples were collected (being extruded aluminum tubes of alloy 3103), divided into 90 for each of the analyzed conditions. This collection took place over 101 non-consecutive days. All samples were manufactured following the same process sheet. Hydro collected these samples as part of a control for batch release. Each batch corresponded to a degreasing basket with a capacity of 330 pieces, totaling a sample space of 59,400 products. The randomly selected samples were crimped using a Hydro universal testing machine configured for compression tests, allowing the determination of minimum crimping force values. The collected data were processed using MINITAB® software for the construction of the process capability study, comparing the samples before and after the improvement process. Data treatment confirmed the effectiveness of the improvement proposal.