The influence of the anodization temperature and voltage on the porosity of the anodization layer on aluminium

Features in aluminium alloy grains and their effects on anodizing and corrosion

“…The effect of the conditions of anodizing (such as applied current density, voltage, type of electrolyte, and temperature) [1][2][3][4][5][6][7][8][9] and intrinsic material factors (such as the presence, types and distributions of second phase particles, alloying elements, and grain orientation) [6,[10][11][12][13][14][15][16][17][18] on the anodizing behaviour and morphology of the anodic films formed on aluminium alloys have been widely researched. With respect to self-ordering of pores, works on the influence of the extent of induced or inherent stress on the anodizing behaviour of aluminium alloys and works on the growth of porous oxide films on defined aluminium crystals have been reported [19][20][21][22].…”

Accurate evaluations of both porosity and tortuosity of anodic films grown on rolled AA 1050 and on rolled or machined AA 2024 T3

“…At a constant forming current density (here J = 0.5 mA cm −2 ), the voltage increases linearly with the gradual filling of the porosity, which results when the filling is integral with a slope break (from m 1 to m 2 ), also called the “knee voltage,” at time t p (Figure ). Experimentally, this knee voltage is not usually a well‐defined slope change but rather a smooth change . The slope then decreases (m 2 < m 1 ) since the growth rate drops, with the porosity (τ forming ) changing from an α value (0 < α < 1) in the porous film to 1 above the filled film.…”

“…The slope then decreases (m 2 < m 1 ) since the growth rate drops, with the porosity (τ forming ) changing from an α value (0 < α < 1) in the porous film to 1 above the filled film. It is then possible to determine the porosity (τ forming ) using the following formula: where T Al3+ is the transport number of Al 3+ ions, assumed to be equal to 0.4.…”

“…A third technique known as "reanodization" (or also the "Dekker-Van Geel" technique) [26][27][28][29][30][31][32] was used; this is based on a second galvanostatic anodization (also called the "forming" step) of a first porous anodic film, in a mixed boric acid-tetraborate electrolyte (H 3 B0 3 0.5 mol L −1 ; Na 2 B 4 O 7 0.05 mol L −1 ). 28,30,32 At a constant forming current density (here J = 0.5 mA cm −2 ), 28,32 the voltage increases linearly with the gradual filling of the porosity, which results when the filling is integral with a slope break (from m 1 to m 2 ), also called the "knee voltage," at time t p (Figure 1). Experimentally, this knee voltage is not usually a well-defined slope change but rather a smooth change.…”

The cracking behaviors of anodic films on 1050 and 2024 aluminum alloys after heating up to 300°C

“…For aluminum alloys, due to the presence of alloying elements, especially copper with high content, the anodizing process and properties of anodic films are significantly influenced, in contrast to pure aluminum. The reason was believed to be related to the presence of second phase particles which affect surface reactivity during pretreatment and anodizing and assist interface reactions, leading to changes in composition and microstructure of the anodic films [9][10][11][12][13]. Other studies suggested [8] that, during anodizing of Al-Cu alloy, copper element was enriched in the alloy immediately beneath the anodic films and was incorporated into the anodic alumina with generation of oxygen.…”