Key factors influencing the stability of silane solution during long-term surface treatment on carbon steel

• The corrosion-resistance time of silane films decreases with increasing cycle numbers.
• The morphology of silane films prepared from aged solution is inhomogeneous.
• Introduction of contamination ions is one reason for the poor property of aged solution.
• Consumption of silane is the other reason for the poor property of aged solution.
• Fe3+ accumulated is the key factor influencing the property of silane solution.

The mixtures of bis-[trimethoxysilylpropyl]amine and vinyltriacetoxysilane were used for surface treatment of carbon steel, aiming to investigate the factors influencing the stability of silane solution during long-term experiment from two aspects. One is the concentrations of contamination ions, and the other is mass of silane consumed per cycle which is calculated according to concentration of Si measured by silicon molybdenum blue photometry. The results indicate that the accumulation of contamination ions, especially Fe3+, is the main factor leading to the condensation between the Si–OH groups in silane solution, which is responsible for the downward stability of silane solution.