Anodized zamac sealing

ABSTRACT

Studies have already shown that zamac anodizing is an alternative to minimize the corrosive effects of the alloy. Other studies, in aluminum, demonstrated that when anodized and sealed by the hot process, it promotes an increase in its resistance to corrosion. However, there are no reports in the literature about heat sealing in anodized zamac. The objective of this work is to identify the effect of sealing, in terms of corrosion resistance, on anodized zamac. For this purpose, industrially sanded and polished pieces of zamac 5 were anodized in 0.3 M oxalic acid electrolyte at different times (5, 30 and 60 minutes), and subsequently sealed in distilled H₂O at 90ºC for one hour. The parts were analyzed using morphological techniques and corrosion tests. The results showed that with increasing anodization time, the bigger crystallites dissolve, originating smaller crystallites until the formation of a smooth layer. In addition, the sealing process promoted hydration of the anodized zamac products. However, with increasing anodizing time, the oxide layer became more compact, due to smaller crystallites, with a decrease in thickness, due to the smooth layer. This resulted in the best anti-corrosive performance of the 5-minute anodized and sealed sample.

Keywords
Zamak; Anodizing; Hot sealing