Cerium-based sealing of PEO coated AM50 magnesium alloy

Abstract

a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Magnesium PEO Cerium Sealing CorrosionEnvironmentally friendly Ce-based sealing post-treatments were developed for PEO coatings on AM50 magnesium alloy. The influence of the Ce(NO 3 ) 3 concentration in the Ce bath and the time of the sealing process were evaluated in terms of morphological and structural properties using SEM, EDS and XRD. Ce content in the layer increased with both the amount of salt in the solution and the time of the sealing post-treatment process due to a higher Ce product accumulation into the pores and cracks of the coatings. Sealed PEO coatings revealed an improvement in the corrosion protection properties as measured by electrochemical impedance spectroscopy. Differences in the corrosion resistance values for the sealed coatings indicate a strong relation between the parameters of the sealing process and its effectiveness, showing higher resistance for the sealed PEO coating developed after 3 h of immersion in 10 g/l Ce(NO 3 ) 3 sealing bath.

Corrosion and mechanical properties of plasma electrolytic oxidation‐coated AZ80 magnesium alloy

“…This fact is due to the particular mechanism of formation of PEO coatings that permit the formation not only of the substrate oxide but also of compounds coming from the electrolyte . In this case, sodium silicates and phosphate were present in the electrolyte, so the composition of the coating resulted in accordance with the one of the electrolyte and also with the ones previously reported in literature . Mg peaks can also be found in the spectra due to the reflection from the substrate.…”

“…However, generally a sealing treatment is necessary in order to ensure sufficient resistance against corrosion . Different types of sealing treatments were performed in literature: with particles in order to give also particular properties to the coating, with rare‐earth based conversion layers, and also with compounds that can ensure active protection . However, due to the economical and practical reasons, linked also with the fact that are the ones used in traditional anodizing, the sealing treatments in boiling water remain the ones mainly used in the industrial world.…”

Characterisation and Electrochemical Evaluation of Plasma Electrolytic Oxidation Coatings on Magnesium with Plasma Enhanced Chemical Vapour Deposition Post-Treatments

“…To overcome this shortfall and to promote further industrial applications, extensive research has been carried out in the last decade focusing on protective coatings for Mg alloys . Among these studies, plasma electrolytic oxidation (PEO) has attracted increasing interest as it is an environmentally friendly technique and can significantly improve the corrosion resistance of Mg and its alloys . During the PEO process, the sample and the stainless steel plate are immersed in an alkaline electrolyte as the working electrode and a counter electrode, respectively.…”

“…[7][8][9][10][11][12][13][14][15] Among these studies, plasma electrolytic oxidation (PEO) has attracted increasing interest as it is an environmentally friendly technique and can significantly improve the corrosion resistance of Mg and its alloys. [7,10,14,[16][17][18][19][20] During the PEO process, the sample and the stainless steel plate are immersed in an alkaline electrolyte as the working electrode and a counter electrode, respectively. When a high voltage exceeding the breakdown value is applied, a ceramic protective coating can be formed on the sample surface by plasma assisted electrochemical reactions.…”

Silicate-based Plasma Electrolytic Oxidation (PEO) coatings with incorporated CeO2 particles on AM50 magnesium alloy

“…In author's previous work [54], the incorporation of Ce species into PEO coating was conducted in a second step with conversion post-treatments based on Ce(NO 3 ) 3 bath. Coatings with Ce compounds revealed a stabilization and increase of the resistance of the inner layer, which might be related to the deposition of Ce 3+ when the pH increases due to the nano-scale corrosion process in the inner layer.…”