عنوان مقاله [English]
In this study, the effect of different surface activation methods on characteristics of phosphate coating, such as morphology and paint adhesion quality, was investigated. The SEM micrographs showed that, surface activation by sandblasting, leads to formation of fine-grained and more compact coating including phosphate crystallites with the average length of 57.65 μm due to increasing the active centers for nucleation. While, the phosphate crystallites size of formed coating on the shot blasted or grinded surface were with the average length of 169.72 μm and 118.14 μm, respectively. Also, the SEM investigations showed that by using rephosphating as an innovative method, further reduction in the phosphate crystallites size to about 24.99 μm was obtained. EDX analysis and further SEM investigation confirmed that the formation of such coating could be in consequence of dissolution of base metal during first stage coverage and entrapping the small debris of initial phosphate layer in these regions, which can be act as nucleation sites during rephosphating. However, paint adhesion increases using phosphate coating, significant improving in adhesion was obtained with applying dense phosphate layer. On the other hand, by formation of denser coating with improved protective properties, the quality of wet adhesion of paint increases.