Citric Acid as an Alternative to Sulfuric Acid for the Hard-Anodizing of AA6061

• Published in: Metals (Basel ) 2021-11, Vol.11 (11), p.1838
• Main Authors: Cabral-Miramontes, José, Almeraya-Calderón, Facundo, López, Francisco Estupinán, Lara Banda, María, Olguín-Coca, Javier, López-León, Luis Daimir, Castañeda-Robles, Ivan, Alcalá, Miguel Ángel Esneider, Zambrano-Robledo, Patricia, Gaona-Tiburcio, Citlalli
• Format: Article
• Language: English
• Subjects: Abrasion resistant alloys; Additives; Aeronautics; Alloys; aluminum alloy; Aluminum alloys; Aluminum base alloys; Anodizing; Citric acid; corrosion; Corrosion currents; Corrosion prevention; Corrosion resistance; Corrosion resistant alloys; Corrosion tests; Current density; Diamond pyramid hardness; EIS; Electrochemical impedance spectroscopy; Electrode polarization; Electrodes; Electrolytes; environmentally friendly; Hard anodizing; Investigations; Mechanical properties; Morphology; Scanning electron microscopy; Spectrum analysis; Sulfuric acid
• ISSN: 2075-4701; 2075-4701
• DOI: 10.3390/met11111838

Hard-anodized is a widely used method in the aeronautical sector to improve aluminum alloys abrasion and corrosion resistance. Aim of this work was to characterize the mechanical properties and resistance hard-anodized aluminum 6061 in citric acid solution as a replacement sulfuric acid solution were investigated. Aluminum alloy 6061 was used as the base material to produce the hard anodizing; this process was carried out in a citric and sulfuric acid solution, applying current densities 3 and 4.5 A/cm2 and subsequently exposed to 3.5 wt. % NaCl solution. Microstructure and mechanical properties of the anodizing material were characterized by scanning electron microscopy (SEM) and Vickers microhardness (HV). Corrosion behavior of the hard-anodized material it was carried out with electrochemical techniques as cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy (EIS) respectively. Results obtained indicated that all samples anodized in citric acid solution showed negative hysteresis and lower corrosion current density (1 × 10−10 A/cm2), indicating generalized corrosion on the material surface. EIS results show that anodizing in citric acid solution and a current density of 4.5 A/dm2 provides better corrosion protection than a sulfuric acid solution.