Effects of Surface Morphology and Coating on the Appearance

by Kang-Yung Peng

Publisher - China Steel Corporation, Taiwan

Category - Engineering & IT

Galvanized Steels (GI) are widely used in appliances, structures and vehicles where the appearance stability is very important. Therefore, the capability against blackening over time is one of the key requirements for GI products. So far lots of efforts have been made for the mechanism and the methods to suppress the blackening process. However, very few studies can clarify individual effects of the substrate and the coating. Hence, in this paper, effects of the GI substrate (surface morphology) and the coating on the appearance stability were investigated side by side. The apparent appearance of coated GI sheets before and after high-temperature-and-humidity storage was quantified by the optical characteristic parameters (85o Gloss value and CIELAB coordinates). Both Gloss and Lightness values decreased after such a treatment. And statistical analysis results simultaneously clarify that (1) the stability of Lightness is “significantly correlated” to “the coating”; and (2) the stability of Gloss is on the other hand strongly correlated to “the substrate”. However, in most cases, the Gloss value changes more than the Lightness when blackening occurs. This suggests that the substrate should usually be more influencing than the coating to the apparent stability of coated GI products.

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