Design And Synthesis Of Novel Thiosemicarbazone Derivatives And Their Corrosion Resistance To Aluminum Alloys

Thiosemicarbazone compounds contain N and S heteroatoms with lone pair electrons,they are classical metal ion chelating agents and can combine with metal ions with empty orbitals,these basic properties can be used as metal corrosion inhibitors.This paper consists of two parts.One is to synthesize and investigate the corrosion resistance of five isatin thiosemicarbazone derivatives(TSC-ISA-R)on aluminum alloy;The second is to supplement and synthesize two isatin thiosemicarbazone derivatives with deformed tetrahedral substituents at the same substituent point and to explore their effects on the inhibition performance of aluminum alloys.The specific research is as follow:(1)Five indocyanine thiosemicarbazone derivatives with different substituents(R=-H,-CH₃,-F,-Cl and-NO₂)at the 5-position of indole ring were synthesized and characterized.Field emission scanning electron microscopy(FE-SEM),X-ray energy dispersive spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS),potentiodynamic polarization analysis(PDP),weight loss measurement,density functional theory(DFT)and molecular dynamics(MD)were used to study the corrosion inhibition of TSC-ISA-R on AA6060 aluminum alloy in acidic chloride-containing medium and the relationship between the corrosion inhibition and substituent effect was studied.The results showed that the inhibition of TSC-ISA-R was strongly correlated with the substituent modification.The corrosion inhibition of TSC-ISA-NO₂ on AA6060 aluminum alloy is better than other derivatives.(2)Two indocyanine thiosemicarbazone derivatives TSC-ISA-R(R=-OCH₃ and-OCF₃)with different substituents(R)on indole ring C5 were synthesized.The corrosion inhibition effect of TSC-ISA-R on aluminum alloy was studied by the similar method as the second chapter.The effect of substituent modification on the corrosion inhibition performance of TSC-ISA-R was obtained.Compared with the second chapter synthesized TSC-ISA-H without C5 substitution,TSC-ISA-OCH₃ has obvious corrosion inhibition effect on the alloy compared with the other two corrosion inhibitors.TSC-ISA-OCH₃ is a cathodic inhibitor,TSC-ISA-OCF₃ is a mixed inhibitor,which mainly hinders the cathodic reaction of AA6060 aluminum alloy.