Aqueous-epoxysilane coating on copper

C. DEYÁ; B. DEL AMO; R. ROMAGNOLI

Porto de Galinhas

Conferencia; XV International Sol Gel Conference; 2009

International Sol-gel Society

Silanes are known to enhance the adhesion between metal substrate and organic coatings [1-3]. Through the oxygen atom the silane bonds covalently to the metal (copper, aluminum, and stainless steel) while the organic part of the molecule interacts with the coating if the silane and the film forming material of the coating were suitable selected. Moreover, the application of silane pretreatments as adhesion promoters for organic coatings is increasing due they offer very good performance and high environmental compatibility. Hence, it is of major importance to test the effect of these compounds on metal corrosion behavior in order to avoid the use of  coupling agents that could stimulate corrosion [4-6]. The aim of this work was to study an aqueous-epoxysilane sol-gel coating applied on copper for corrosion protection. Different curing temperatures (100 and 200ºC) and times (0.08, 0.5, 1 and 2 hours) were studied. The action of glycidoxypropyltrimethoxysilane (glymo) sol-gel coating applied on copper was assessed by polarization tests after 1, 6, 25 hours and 4 days of immersion in a 0.5M NaCl. Corrosion potential of coated copper was also measured during two hours. Coated panels were placed in the salt spray chamber and rusting and blistering degrees were evaluated after 18 and 90 hours. The surface of the salt spray exposed panels was observed by scanning electron microscopy (SEM) while corrosion products formed on it were characterized by energy dispersive X-ray analysis (EDXA). According to the results the variables under study (time and temperature of curing) are important in the protective behavior of the silane film. Moreover, glymo do not stimulate corrosion in any case. Electrochemical and salt spray tests showed that the best protection was afforded by samples with short curing time. The corrosion products formed on the panels were, mostly, oxides; little amounts of chloride compounds were observed. It is worthwhile testing glymo as adhesion promoter of modified epoxy coating on copper.