Enhancement of the corrosion protection performance, cathodic disbandingresistance and adhesion properties of epoxy coating through treatment of steelsubstrate by Nano structured vanadium-based conversion coating In thepresence of Ni ions

Corrosion resistance of the mild steel must be improved before any outdoor applications byvarious techniques such as cathodic/anodic protection, coatings, surface treatments, inhibitors andapplication of anti-corrosion pigments. It is known that chemical conversion coatings are one of the coatings applied on the VNiCC samples were greater than VCC sample. In addition, theadhesion loss of the coating applied on the VNiCC substrate was lower than other samples. Also,the results obtained from EIS and cathodic disbonding test clearly revealed that the VNiCC couldenhance the corrosion protective performance and reduced cathodic disbonding of the epoxycoating than other samples.the most cost-effective methods of surface modification. They facilitate bond formation betweenthe substrate and the organic coating together with improving corrosion resistance. Hence, in thisstudy nanostructured vanadium conversion coatings were deposited on the surface of mild steel(st37) on the basis of vanadium (VCC) and vanadium-Nickel (VNiCC) based conversion coatingsolutions. An epoxy/polyamine coating was then applied on the VCC and VNiCC substrates. Thesurface characterization was performed by field emission scanning electron microscope (FESEM)and atomic force microscopy (AFM) measuring device. The adhesion strengths of theepoxy coatings applied on the surface treated samples were measured before and after 30 days ofimmersion in 3.5 wt.% NaCl solution by a pull-off test. In addition, The effect of VCC andVNiCC treatment on the epoxy coating performance was studied by electrochemical impedancespectroscopy (EIS) and cathodic disbonding (CD) tests. FE-SEM and AFM study show that theVNiCC is denser, More continuous and more surface roughness than VCC. The dry and recovery(adhesion strength after 30 days immersion in the 3.5 wt% NaCl solution) adhesion strengths of

کلیدواژه ها:

Nano structured vanadium-based conversion coating ، Nickel ، Corrosion resistance ، Epoxy coating ، cathodic disbanding ، FE-SEM/AFM