Thermal effects associated with hard anodizing of cast aluminum alloys

Abstract

Hard anodizing of three different cast aluminum substrates (i.e. Al99.8 wt%, Al-10 wt% Si, Al-10 wt% Si-3.5 wt% Cu) was performed in 2.25 M H 2 SO 4 electrolyte at 0°C. The effects of substrate composition, current density and convection regime on electrode temperature evolution were investigated. Temperature transients followed the voltage transients during anodizing. At a current density of 6.0 A dm )2 , the electrode temperatures increased with alloying whereas at 30 A dm )2 the temperature reached a steady value around 65°C and severe oxide dissolution effects were visible on the surface of the anodized specimens. Further, at this current density and under forced convection regime, highest temperature values were recorded for the Al99.8 wt% substrate and were accompanied by fluctuations. Forced convection significantly reduced the electrode temperatures during the non-uniform oxide growth for all three compositions and increased the oxide layer thickness.

Anodizing Al–Si Foundry Alloys: A Critical Review

“…[35,45] In contrast, when the anodic layer cracks and re-anodizes due to the presence of high levels of intrinsic stresses, fluctuations in the voltage measurements are recorded. [45,75,76] Therefore, in the voltage-time graph, the voltage fluctuations in the steady-state region correspond to the formation of cracks in the anodic layer.…”

“…This technique was used by Fratila-Apachitei et al [35,76,77] and Gastón-García et al [45] to analyze the growth evolution of the oxide under different anodizing parameters. In particular, they studied the influence of the applied current density on the formation of the anodic layer.…”

Anodizing of aluminium under applied electrode temperature: Process evaluation and elimination of burning at high current densities

“…In a limited number of studies the electrode temperature is measured during anodizing and, these studies clearly indicate the influence of this parameter on local oxide growth [2][3][4][5][6]. In other papers the temperature of the aluminium is actively influenced during anodizing, either to evaluate the effect on local oxide growth [7], either to improve the temperature control of the process [8][9][10].…”

Effects of surface treatments of AA 2024-T3 aluminum sheet on bonding to epoxy-based film adhesive

“…The cellular structure, thickness, and pore diameter vary greatly depending on the voltage applied and the treatment reagents used. To a certain degree, the thickness of the oxide layer offers excellent corrosion resistance and affects the adherent properties of substance [16,17] . (Figure 2A).…”