Effect on temporary protection and adhesion promoter of silane nanofilms applied on electro-galvanized steel

Abstract

In this paper, the effectiveness of γ-mercaptopropyltrimethoxysilane (MTMO) films as temporary corrosion protection and adhesion promoter on electro-galvanized steel was studied. The films were synthesized from hydrolyzed MTMO with ethanol or methanol, applied by immersion on electro-galvanized steel and cured under different conditions. The porosity of the coating was evaluated by cyclic voltammetry, the corrosion behavior by polarization curves and the protection degree by exposure in the humidity and prohesion chambers. The films were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). From the obtained experimental results, it was concluded that this protection is markedly affected by the coating curing conditions and the alcohol used in the hydrolysis. MTMO is a good temporary protector against electro-galvanized steel corrosion in high humidity environment but it is less effective in environments containing aggressive ions such as Cl- and SO4-2. In a second stage, pretreated samples were coated with an alkyd anticorrosive paint and exposed to the salt spray chamber. Dry adhesion tests as well as SEM and EDS studies were also done in order to know the nature of the disbonding fails (adhesion or cohesion).