Enhancement of corrosion protection of AISI 201 austenitic stainless steel in acidic chloride solutions by Ce-doped TiO₂ coating

Highlights

• A ceramic coating of Ce-doped TiO2 was electrodeposited on medium-Mn AISI 201 steel.

• The coating morphology shows a dendritic pattern with a uniform thickness of ~1 μm.

• The coating constitutes a protective passive film in acidic chloride solutions.

• Slow degradation in acidic chloride media due to high stability of Ce-doped TiO₂

• Pitting and corrosion layers were promoted on the bare steel during corrosion tests.

Abstract

Ce-doped TiO₂ coatings were applied by electrodeposition on a low-nickel austenitic stainless steel (AISI 201) bearing 8 wt% Mn to improve the electrochemical properties in acidic chloride solutions. Characterization of the Ce-doped TiO₂ coatings was performed by a scanning electron microscope equipped with energy dispersive X-ray spectroscopy (EDS) to study the tiny features. The corrosion behavior of the bare and coated steel was evaluated in aqueous acidic chloride solutions mixing with different chloride concentrations, 1 mol·L⁻¹ H₂SO₄ with 0–1.5% NaCl. Potentiodynamic polarization tests were conducted to evaluate the corrosion characteristics, corrosion potential E_corr and corrosion current density i_corr. Further study concerning the weight loss (WL) using immersion tests for the long-term was conducted to determine the bare and corresponding coated steel's equivalent corrosion rates.

It was found that the electrodeposited Ce-doped TiO₂ coatings with a layer thickness of ~1 μm enhance the corrosion resistance of the coated steel in the acidic chloride solutions compared to its counterpart, the bare steel. The polarization tests showed that the i_corr of the Ce-doped TiO₂ coated steel significantly declined to a half value of the bare steel. The E_corr for all coated specimens shifted to a more positive value when compared with those of the bare steel. The WL measurements displayed that the bare AISI 201 steel experiences intensive corrosion degradation in the presence of a low concentration of chloride ions. However, the Ce-doped TiO₂ coatings significantly resist the aggressive chloride ions and consequently increase the corrosion resistance of the steel.