A comparative study on UV degradation of organic coatings for concrete: Structure, adhesion, and protection performance

• Published in: Progress in organic coatings Vol. 149; p. 105892
• Main Authors: Wang, Haochuan, Feng, Pan, Lv, Yadong, Geng, Zifan, Liu, Qi, Liu, Xin
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.12.2020; Elsevier BV
• Subjects: Adhesive strength; Aging; Chloride resistance; Comparative studies; Concrete; Concrete structures; Contact angle; Degradation; Fourier transforms; Infrared spectroscopy; Microscopy; Morphology; Organic coatings; Polyureas; Porosity; Protective performance; Pull off tests; Ultraviolet radiation; Water resistance; Weatherability; Wettability; Aging; Weatherability; Concrete; Protective performance; Organic coatings
• ISSN: 0300-9440; 1873-331X
• DOI: 10.1016/j.porgcoat.2020.105892

•The role of bulk degradation and adhesion loss on the protection performance of coatings under UV irradiation is studied.•The degradation of polyurea and epoxy coatings under UV irradiation is compared.•The changes in chemical structure, water resistance and adhesion strength of coatings after UV irradiation are discussed.•The critical role of adhesion on the chloride ion penetration resistance of coatings after aging is identified. Organic coatings have been widely used to protect concrete structures from the aggressive environment and improve their reliability. However, there is a lack of clear understanding on how environmental stressors contribute to the degradation and, ultimately the loss of protection function of organic coatings. In this study, comparative degradation studies were carried out on two kinds of coatings, namely polyurea and epoxy coatings, with the major focus on the relationship between their bulk degradation, loss of adhesion and the deterioration of protection performance. Samples were all subjected to ultraviolet (UV)-condensation exposure up to about 1440 h. The changes in the surface morphology, internal pore structure, wettability and chemical structure of aged coating surface were characterized via scanning electronic microscopy (SEM) laser scanning confocal microscopy (LSCM), static contact angle measurements, and Fourier Transform Infrared Spectroscopy (FT-IR) respectively, while the water resistance and adhesion strength between coatings and concrete were studied by water sorption and pull-off tests separately. The results showed that UV irradiation induced significant morphological and chemical changes in the epoxy coatings, while the changes in the polyurea coating were minor. However, due to the higher loss in adhesion, it was interestingly found that the chloride resistance of polyurea coating was reduced even more pronouncedly than that of epoxy coating after aging. This study has clearly demonstrated the strong dependence of the protection performance of coatings for concrete on their adhesion loss besides the bulk degradation induced by the aging process.