Effect of Curing Agent towards Corrosion Resistance by Polarization Study

5 Effect of Curing Agent towards Corrosion Resistance by Polarization Study 

The description of coating systems under investigation is as follows System 1 is DESMODUR-i-DEGBA/ POSS -NHj cured by Aradur 140, and System 2 is DESMODUR+DEGBA cured by Aradur 140. System 3 and System 4 refer to DESMODUR+DEGBA/POSS-NH cured by XY54 and DESMODUR+DEGBA cured by XY 54, respectively 

The incorporation of POSS NHj enhances the corrosion resistance of the phosphate-modified epoxy system. System 1 dominates the corrosion resistance because of the presence of POSS-NHj, which acts as nanostructured crosslinking sites to form coatings characterized with high crosshnk density, thereby resulting in tough and relatively hard protective films on metals. 

The polarization study of Systems 1, 2, 3 and 4 after 30 days of immersion in NaCl shows Systems 1 and 2 shift towards the anodic side, while the latter two shift towards the cathodic side. This may be explained due to the molecular structure and it electrons of nitrogen and sulphur atoms which adhere strongly onto the metal surface, whereas the inferior corrosion resistance of Systems 3 and 4 may be due to the water absorbing nature of the polyamidoamine curing agent. 

The greater semicircle in the Nyquist plot for the coating System 1 alone indicates better corrosion resistance, which may be attributed to the presence of the imidazoline 

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