Sealing effect on corrosion resistance of boric sulfuric acid anodizing on AA2024

Abstract

Aluminum is widely used due to its excellent properties, lightweight and thermal conductivity. However, when used in aircraft applications, it can cause corrosion and sticking, compromising safety. To address this issue, anodizing is used to improve aluminum's corrosion resistance and adhesion. In this study, the AA2024 material was anodized using the boron-sulfuric acid anodization (BSAA) process, followed by a sealing process using acetic acid. This sealing process forms an oxide layer on the aluminum's surface, which reduces the corrosion rate. The study investigated the effects of anodization voltage and time on the results of BSAA anodization through quantitative and qualitative measurements, including corrosion resistance, potentiodynamic polarization, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The results showed that samples anodized with a gasket could reduce the corrosion rate by up to 85 % compared to those without a gasket and substrate. The most significant reduction in corrosion rates occurred at an anodization voltage of 10 V and an anodization time of 15 min. The potentiodynamic test results indicated that the Tafel plot during sealing lies in the cathodic region where the corrosion current density decreases with increasing voltage. SEM observations revealed that the anodizing process could provide an oxide layer on the samples' surface, while the sealing process creates a smooth surface. EDS analysis showed that an oxide compound was formed in an oxide bond state after the sample surface was subjected to the sealing treatment. Overall, the study demonstrates the effectiveness of BSAA anodization in improving corrosion resistance and highlights the importance of considering the anodization parameters

Effect of anodizing on aluminum alloy 2024 with boric sulfate acid in medium 3.5 % NaCl

“…It creates a barrier that prevents direct contact between the aluminum and corrosive substances in the environment [8]. The investigation highlights that the effectiveness of the sealing procedure is influenced by the timing of anodization [13]. The correlation between the duration of anodizing and the subsequent decrease in corrosion rate becomes more evident as the duration of anodizing is increased, especially after the sealing procedure is applied.…”

“…One approach that has been receiving increasing interest is Boric Sulfate Acid Anodizing. This process includes the deliberate electrochemical oxidation of the aluminum surface in an electrolyte solution that contains boric acid and sulfate ions [13,16].…”

“…The study conducted in the paper [13] examines the influence of the sealing process on the corrosion resistance of AA2024 aluminum alloy. The research utilizes a suitable methodology involving anodizing with boric sulfuric acid, sealing the specimens, and performing corrosion resistance tests.…”

“…Boric sulfate acid's anodizing process may be modified to produce the required coating thicknesses and surface properties by modifying parameters such as voltage, current density, and anodizing duration [13,14]. This allows for a greater degree of control over the final product.…”