Colour resistance of Zn–Ti coatings to corrosive environments
Adding titanium to a hot-dip galvanising bath, a coloured oxide film due to interference effect was obtained on iron samples; different colours were achieved varying the bath temperature in the range of 520–600°C. In this paper, the resistance of three colours (yellow, purple and light blue) to four corrosive environments (urban, marine, industrial and rural) has been investigated by means of an experimental approach: two specimens of each colour with titanium percentage of 0.2% were exposed for 1 year in each environment and colour measurements in CIE Lab coordinates have been recorded at fixed time intervals. Modification of colours on samples due to corrosion effects of different chemical agents was evaluated calculating CIE colour difference. Results demonstrated that the colour of the coatings have a good resistance to all kinds of atmospheres tested; so the performance of this galvanising bath resulted adequate for architectural application.