Corrosion behaviour of polyester and fluoropolymer coatings on coil coated stainless steel

Abstract

Coil coated stainless steel is a new material for applications in civil and industrial fields with the purpose of reducing maintenance costs and increasing the service life of the products. The corrosion behaviour of different types of stainless steel coated with both polyester and fluoropolymer films of different thickness has been studied by means of AC impedance spectroscopy (EIS), the break-point frequency method and scanning electron microscopy analysis (SEM). The charge-transfer resistance and double-layer capacitance for both polyester and fluoropolymer coatings on stainless steel reveal no reactivity, corrosion or disbonding on the substrate. The changes of pore resistance, coating capacitance and break-point frequency over time indicate the different corrosion behaviour of polyester and fluoropolymer coatings due to their different chemical structure and film thickness. On the other hand, the polyester coatings on phosphatized galvanized steel exhibit quite different behaviour in regard to the same coatings on stainless steel. Different types of stainless steel as substrate cause the different corrosion behaviour of the investigated polyester and fluoro-polymer coatings. It has been observed that stainless steel which contains more nickel and molybdenum shows higher resistance to corrosion attack in chloride environments.