Inorganic And Organic Materials, Composite Film On Carbon Steel Corrosion Behavior Of Influence

The loss cost by marine corrosion has increased year by year because many marine engineering had built for marine development and utilization. Corrosion can reduce load carrying capacity either by generally reducing its size or by pitting, both of which can lead to huge economic losses or even catastrophic accident. Thus the research on metal corrosion and protection in seawater has important application significance and economic value.In this work, two kinds of inorganic/polyelectrolyte composite film (zinc oxide (ZnO)/poly (diallyldimethylammonium) (PDDA) composite film and ZnO/chitosan (CS) composite film) and a kind of inorganic particles/metal composite film (zinc (Zn)/silicon dioxide (SiO₂) composite film) have been fabricated by potentiostatic electrolysis method. The character of composite films was studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and fourier transform infrared spectrometer (FT-IR). The corrosion resistance of composite film was studied by polarization curves method. The main conclusions are shown as follows:1,The PDDA thin film has been fabricated on carbon steel surface by self-adsorption method. Polarization curves indicated that compared with other conditions the film fabricated in 2 g L^-1 PDDA solution for 1 h had optimal corrosion resistance. SEM results indicated that compared with bare carbon steel, the sample with PDDA film had no corrosion products on surface after immersion in sodium chloride (NaCl) solution for 2 h. This result indicated PDDA has potential application in carbon steel corrosion protection field.2,ZnO film has been fabricated on the carbon steel surface by potentiostatic electrolysis method. The influence factors of corrosion resistance, such as temperature, concentration, potential and stir rate were studied. The results indicated that compared with other conditions the best condition for ZnO electrodeposition was zinc nitrate (Zn(NO₃)₂) concentration, 5 mM, potential, -1.2 V, stir rate, 200 r min^-1.3,A composite film consisting of ZnO and PDDA, has been fabricated on a carbon steel substrate by an potentiostatic electrolysis method. Polarization curves showed that compared with other conditions the composite film fabricated at the PDDA concentration of 2 g L^-1 had the best corrosion resistance. XRD results indicate that ZnO could be fabricated by electrodeposition in composite films. FT-IR results evidence the existence of PDDA in ZnO/PDDA composite film. SEM results show that compared with ZnO film, the composite film becomes more compact and smooth.4,ZnO/CS composite film was obtained on the carbon steel surface via potentiostatic electrolysis method. It is shown that compared with other conditions the ZnO/CS film obtained at the concentration of 0.6 g L^-1 has the best corrosion resistance. XRD results indicate that ZnO could be fabricated by electrodeposition in composite film. FT-IR results evidence the existence of CS in composite film. SEM results demonstrate that the composite film was much smoother and crack free. This was attributed to the good film-form property of CS.5,A Zn/SiO₂ composite film has been electrodeposited on the carbon steel surface via adding tetraethylorthosilicate (TEOS) in Zn(NO₃)₂ solution. Polarization curve results showed that compared with other conditions the composite film obtained at the TEOS concentration of 0.012 M had the best corrosion resistance. SEM results indicated that the film surface became compact with TEOS's addition and the film showed best quality when the concentration was 0.012 M. XRD results showed that the product was ZnO when no TEOS was added. The products were Zn and SiO₂ when TEOS concentration was 0.012 M. Electrochemical impedance spectroscopy results indicated that the impedance of the film decreased with immersing time within 120 h, which could be attributed to the penetration process of electrolyte in solution. However, the impedance presented an increases trend with the immersion time after 120 h, which was a result of building-up of zinc corrosion products on coating surface. This trend was in accordance with the change of charge transfer resistance and film resistance.