Influence of post-treatment time of trivalent chromium protection coating on aluminium alloy 2024-T3 on improved corrosion resistance

Francesco Di Franco, Antoine Seyeux, Philippe Marcus, Jolanta Światowska, Dimitri Mercier, Alexandre Romaine, Philippe Marcus, Jiantao Qi, Francesco Di Franco, Anca-Iulia Stoica, Sandrine Zanna

Risultato della ricerca: Articlepeer review

10 Citazioni (Scopus)

Abstract

Low corrosion protection performances of Trivalent Chromium Process (TCP)coatings with reference to Chromium Conversion Coatings (CCC)deposited on aluminium alloys can be overcome by application of post-treatment processes. This work shows the effect of post-treatment bath (containing hydrogen peroxide and lanthanum salt)on the chemical composition, structure and the corrosion performances of TCP coating deposited on AA 2024-T3 aluminium alloy. Different times of post-treatment bath were applied on the TCP coating and the samples were analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), X-ray Photoelectron Spectroscopy (XPS)and Glow Discharge-Optical Emission Spectrometry (GD-OES). The ToF-SIMS and GD-OES depth profiles show that the post-treatment time has no influence on the thickness of the TCP coating and on its bi-layered structure. It is composed of an outer layer, rich in zirconium and chromium oxides and an inner layer rich in aluminium oxides and oxy-fluorides. 3D ToF-SIMS images reveal an enrichment of Cr and Zr-like species over the surface of intermetallic particles with reference to alloy matrix, whereas a homogenous distribution of La is observed. The analysis of in-depth distribution shows that La is present principally in the outer part of the TCP coating. The La concentration increases with increasing post-treatment time. The effect of post-treatment time on protection was evaluated by Electrochemical Impedance Spectroscopy (EIS)and Linear Sweep Voltammetry (LSV)in a 0.001 M NaCl + 0.1 M Na 2 SO 4 electrolyte. The increased post-treatment time enhances the cathodic inhibition against oxygen reduction. The post-treatment provides improved coating homogeneity and sealing properties.
Lingua originaleEnglish
pagine (da-a)186-197
Numero di pagine12
RivistaSURFACE & COATINGS TECHNOLOGY
Volume369
Stato di pubblicazionePublished - 2019

All Science Journal Classification (ASJC) codes

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  • ???subjectarea.asjc.3100.3104???
  • ???subjectarea.asjc.3100.3110???
  • ???subjectarea.asjc.2500.2508???
  • ???subjectarea.asjc.2500.2505???

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