Electrochemical impedance spectroscopy study of the effect of curing time on the early barrier properties of silane systems applied on steel substrates

Silane-based pretreatments have emerged as a valuable ecologically acceptable alternative to the chromating process. The application process of these pretreatments involves a series of fundamental variables whose optimisation is imperative in order to form a silane layer with good behaviour properties at the interface. One of the most important variables is the silane layer curing process, during which an interfacial network that delays the entry of aggressive species to the metallic surface is formed. The present work studies the effect of curing time on the barrier properties of two types of silane, 3-aminopropyltriethoxysilane and bis-3-triethoxysilylpropylamine, applied on steel substrates, with or without the subsequent application of an alkyd-base paint. Electrochemical impedance spectroscopy (EIS) shows how the silane layer curing process influences its barrier properties and thus its corrosion protection properties.