Improvement of Anticorrosion Properties of Epoxy Primer Coating on Aluminum Alloy 2024-T3 by Thiosemicarbazone Derivatives

The effect of adding thiosemicarbazone derivatives on the anticorrosion properties of epoxy primer coatings on aluminum alloy 2024-T3 was investigated. (E)-2-(2,4-dihydroxybenzylidene)hydrazinecarbothioamide (2,4-DHC), (E)-2-(3,4-dihydroxybenzylidene)hydrazinecarbothioamide (3,4-DHC), and (E)-2-(2,3,4-dihydroxybenzylidene)hydrazinecarbothioamide (2,3,4-THC) were supplemented to epoxy primer that is generally used in aircraft paint systems; and its anticorrosion property was examined by electrochemical impedance spectroscopy and salt spray test. Field emission scanning electron microscopy and energy dispersive x-ray analysis were used to study the surface topology of the coating system. 2,4-DHC and 3,4-DHC doped primer coating exhibits good barrier properties, while 2,3,4-THC doped primer coating exhibits good barrier properties along with active corrosion protection

A Study of Corrosion Behavior of (E)-2-(3,4-dihydroxybenzylidene)hydrazinecarbothioamide and Bis [[3,4-dihydroxyphenylmethylene] Carbonothioicdihydrazide]-Sealed Anodized AA2024-T3

Anodizing is the process of developing an oxide layer on a metal surface. It enhances the corrosion barrier stability of aluminum and its alloys. Chromic acid is universally used as an electrolyte in an anodizing process, but it is not preferred for the anodizing process due to its carcinogenic effect. The aim of present investigation, a chromate-free (E)-2-(3,4-dihydroxybenzylidene)hydrazinecarbothioamide (DHC) or Bis [[3,4-Dihydroxyphenylmethylene]carbonothioicdihydrazide] (DCT)-sealed sulfuric acid anodic oxide coating was developed on AA2024-T3. The 10 wt% H2SO4 was used as an electrolyte in the anodizing process. The results obtained from field emission scanning electron microscopy analysis showed effective surface modification after DHC or DCT sealing. The potentiodynamic polarization curve and electrochemical impedance spectrum were used to study the barrier stability of the created oxide layer on alloy surface against corrosive media (3.5% NaCl). Potentiodynamic polarization results showed a significant difference in corrosion potential value and corrosion current density value after sealing with DHC or DCT. The electrochemical impedance spectrum clearly showed increases in the barrier stability of the sealing oxide layer compared to the plain oxide layer. The salt spray test was used to study the accelerated corrosion of samples. All obtained results confirmed that sealing of organic inhibitors enhances the barrier stability of the anodized aluminum alloy and the order of corrosion protection efficiency is Ox < Ox-DHC < Ox-DCT

Corrosion inhibition of 2024-T3 aluminum alloy in 3.5% NaCl by thiosemicarbazone derivatives

Three thiosemicarzone derivatives, namely (E)-2-(2-hydroxybenzylidene) hydrazinecarbothioamide(MHC), (E)-2-(2,4-dihydroxybenzylidene)hydrazinecarbothioamide (DHC) and (E)-2-(2,3,4-trihydroxybenzylidene)hydrazinecarbothioamide (THC) were synthesized and their corrosion inhibition action on 2024-T3 aluminum alloy was studied in 3.5% NaCl solution. The surface morphology and surface composition of the corroded alloy were examined using FESEM, 3D profilometry, EDX spectroscopy and X-ray photoelectron spectroscopy. The synthesized inhibitors were found to provide corrosion protection on AA2024-T3 by forming an adsorbed layer of the complex on the alloy surface. They exhibited inhibition efficiency in the order, MHC < DHC < THC. Quantum chemical calculations corroborated the experimental results