Formation and characterisation of a chromate conversion coating on AA6060 aluminium

Nanostructured surface pre‐treatment based on self‐assembled molecules for corrosion protection of Alclad 7475‐T761 aluminum alloy

“…Conversion treatments based on chromate compounds, containing hexavalent chromium, chromium (VI) or, simply Cr (VI), provide many advantages, such as low cost, easy application, promote excellent protection against localized corrosion, and favors adhesion to paints and adhesives [1][2][3][4][5][6][7][8][9][10]. However, chromate solutions cause large environmental and health related problems, because they contain Cr (VI) compounds that have several toxic effects.…”

“…However, chromate solutions cause large environmental and health related problems, because they contain Cr (VI) compounds that have several toxic effects. Due to pressures from health and environmental legislation, researchers have devoted attention in the development of alternative coatings of lower toxicity than yellow chromatizing conversion coating for corrosion protection of metallic materials [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Consequently, there has been an upsurge of interest in the corrosion prevention of aluminum alloys using nanostructured surface pre-treatments based on selfassembled molecules (SAMs) [15][16][17][18][19][20][21][22].…”

Corrosion behaviour of a 2219 aluminium alloy treated with a chromate conversion coating exposed to a 3.5% NaCl solution

“…On the chromate treated specimens, the barrier film prevents severe anodic attack of the aluminium at the intermetallic/matrix boundary and the intermetallic dissolution is occurring as a result of the multi-phase nature of the particle and the local electrochemical cells which are formed at the surface. Finally, however, it should be noted that for the Alodine coated alloy, deposition of aluminium corrosion products on the matrix surface is evidence that the coating is not a total barrier and Al is being dissolved from the matrix surface, confirming the porous and cracked nature of this layer, as observed by Lunder et al [18]. Consequently, crevice attack at the intermetallic/matrix interface may occur after longer exposure times.…”

“…Furthermore it was observed that the ageing process produces a developing network of micro-cracks which a limited Cr(VI) reservoir is unlikely to repair [17]. Lunder et al [18] conducted a SEM and TEM analysis of the section of the 6060 aluminium alloy treated with a chromate conversion coating. They observed the presence of numerous pores and cracks in the chromate layer, which may represent rapid diffusion pathways from the external environment to the aluminium substrate.…”

Microstructural and Compositional Characterisation of Chromate Pretreatment on Aluminium

“…Unfortunately, hexavalent chromium present in chromate conversion coating (CCC) formulations as well as in the dried coatings [1][2][3][4][5][6] has been listed as a possible carcinogen. Consequently, active investigations [1,[7][8][9][10][11][12][13][14] are on processes and formulations to replace chromate's corrosion protective properties and improved adhesion of subsequently applied finishes on aluminium and other alloys.…”