Influence of trivalent chromium process (TCP) concentration on the anti-corrosion protection of 2024-T3 aluminium alloy

OpenAlex İngilizce

In the present work, the surface of 2024-T3 aluminium alloys was coated with different concentrations (25, 35, and 50 wt.%) of the trivalent chromium process (TCP), and they were evaluated by comparing them to hexavalent chromium coatings (HCC). The findings show that TCP coating had a porous surface regardless of the concentration of TCP coating while the HCC exhibited a cracked pattern. The TCP coating increased the surface roughness as well as the wettability compared to HCC. The immersion test in 3.5 wt. % NaCl solution revealed that the open circuit potential (Eocp) of coated samples was more positive than that of the uncoated sample. However, the HCC coating was slightly more anodic after half of the immersion. The potentiodynamic test confirmed the formation of a passive region for all samples. Furthermore, the corrosion potential (Ecorr) and the critical pitting potential (Epit) were more positive for the lowest concentration coating. The polarisation resistance of the samples suggested that the HCC coating was superior to TCP coatings. In general, the low concentration of TCP coating improved the corrosion protection of 2024-T3 but not better than HCC coating due, probably, to the porous surface morphology.