In recent years, the development of coating materials has gone beyond material protection to integrating numerous high-tech elements and health concepts. For an island country like Taiwan, since building structures are constantly exposed to high humidity and chlorine ions, if the design for protection of metal material is not appropriate, constant replacement or removal of the material will be necessary due to corrosion or the unappealing appearance. In many buildings that need to have an appealing appearance, the limiting factor of the life expectancy of coating materials is not when the coating loses its protective properties, but when the luster of the coating deteriorates, affecting the exterior appearance of the building. Therefore, this research focuses on experiments involving photodamage resistance. Besides categorizing the durability and weathering resistance of each coating material, protection mechanics and deteriorating methods have also been explained. Coupled with actual deterioration experiments, the relationship between exposure to Taiwan’s seasonal weathers and environment and the acceleration of deterioration is established.
Four kinds of coating materials (acrylics, epoxy resins, PU, and fire retardant paint) were used on carbon steel. Two deterioration processes—accelerated deterioration of 2000 h of salt mist testing combined with sunlight and 6 months of natural exposure deterioration—were employed to discuss the photodamage resistance properties of each coating material.
Experimental results show that before the coatings were exposed to accelerated and natural deterioration, epoxy resins exhibited the best luster. However, after simulated sunlight was used to accelerate the deterioration, the resins exhibited a large change in luster as well as increased surface roughness. The fire retardant paint began to crack and peel. All coating materials showed a significant change in color as well as loss in luster when exposed to sunlight-accelerated deterioration. In terms of applications, a few suggestions are given below:
1. When epoxy resins are used for coating the exterior of a building, visual effects due to sunlight should be considered.
2.Fire retardant paint is mostly used inside buildings as fire-resistant materials. If used on the exterior, according to experimental results of this paper, peels and cracks occur. It is suggested that fire retardant paint be employed for interior use only.
3.Among the four coating materials, for use on the exterior for long periods of time, fluoro acrylics and PU are suggested, since they have relatively stronger resistance towards photodamage compared to the other two.