Functional anti-corrosive and anti-bacterial surface coatings based on mercaptosuccinic and thiodipropionic acids and algae oil as renewable feedstock

Renewable source based anticorrosive and antimicrobial polyesteramide polyols were synthesized by reacting algae oil with diethanolamine and thio diacids viz. mercaptosuccinic (MSA) and thiodipropionic (TPA) acids. The confirmation of structures and molecular weights of prepared polyols were done by H-1 NMR and FTIR spectroscopic techniques, and size exclusion chromatography (SEC), respectively. The polyols were used to prepare PU which showed excellent adhesion (100%) as compared to algae oil fatty amide (AOFA) (88%) high gloss (118 and 115). This PU passed flexibility test and showed good chemical resistance in comparison to the AOFA based PU coatings. The prepared PU coatings were checked for the anticorrosive property by dipping and electrochemical method performed against 3.5 wt% NaCl and 5 wt% HCl corrosive media. The PEA- PU possessed lower corrosion rate (mm/year) and I-corr values as well as high polarization resistance (R-p) and inhibition efficiency, than uncoated (blank) and AOFA based PU (PU-AOFA). Both MSA and TPA based PU coatings showed good antimicrobial potential and reduction in bacterial attachment, against Gram - negative (E. coli) and Gram - positive (S. aureus) bacteria in comparison to the control and AOFA PU coatings as observed through SEM and the thermal stability of modified PUs was also improved.