Effect of Micro-Zone pH Gradient on AM60B Vanadate Film and Corrosion Behavior

Abstract:

To further study the formation and corrosion mechanisms of AM60B vanadate films, a vanadate coating was synthesized on AM60B substrate via a chemical conversion at 50°C. The morphologies of the films and the corrosion samples were observed by using scanning electron microscopy(SEM), energy dispersive X-ray analysis(EDAX) was used to analyze the elemental distribution of the film surface and the Electrochemical Impedance Spectroscopy(EIS) and the polarization curves of the films were tested by an electrochemical workstation. The morphology of conversion film is layered structure with white balls. V element preferentially deposits near the base end and the V-rich phase is easily generated on the β-phase(Mg₁₇Al₁₂). In the course of corrosion, corrosion begins near the α-phase(Mg). During the processes of observation and analysis, the concept of micro-zone pH gradients was discovered and applied, and attempts were made to explain some observed phenomena by using this concept. The results show that the concept of pH gradients in micro zones can be used to explain the film formation and corrosion mechanisms well.

• Periodical: Solid State Phenomena (Volume 295)
• Pages: 21-27
• DOI: https://doi.org/10.4028/www.scientific.net/SSP.295.21
• Online since: August 2019
• Authors: Hua Bing Jing, Zu Dong He, Su Qiu Jia*
• Keywords: AM60B, Conversion Film, Corrosion, Mechanism, pH Gradient, Vanadate

References

[1] I. Sciscenko, I. Pedre, A. Hunt, H. Bogo, G.A. González. Determination of a typical additive in zinc electroplating baths[J]. Microchemical Journal, 2016,127.

DOI: 10.1016/j.microc.2016.03.015

[2] Mohammed Shahien, Masato Suzuki. Low power consumption suspension plasma spray system for ceramic coating deposition[J]. Surface & Coatings Technology,(2016).

DOI: 10.1016/j.surfcoat.2016.07.040

[3] Hong Hong Shao, Zi Hong Zhu,Xue Li Liu. Corrosion Resistance and Blood Compatibility of AZ31B Mg Alloy with Anodic Oxidation/TiO2 Composite Film[J]. Journal of Biomimetics, Biomaterials and Biomedical Engineering,2015,4059(23).

DOI: 10.4028/www.scientific.net/jbbbe.23.1

[4] Wen Zhan, Xiaohui Liu, Chensi Lu,Gui Ouyang. The Property of Colored Chemical Conversion on Various Metals with Iso-solution[J]. Procedia Engineering,2017,174.

DOI: 10.1016/j.proeng.2017.01.149

[5] Matilda Zemanová, Ján Lokaj, Mária Karľová, Jana Madejová. Influence of pre-treatment on zirconium based conversion coating on AA2024[J]. Acta Chimica Slovaca,2017,10(2).

DOI: 10.1515/acs-2017-0018

[6] M.A. Gonzalez-Nunez, C.A. Nunez-Lopez,P. Skeldon G.E. Thompson,H. Karimzadeh,P. Lyon, T.E. Wilks. A non-chromate conversion coating for magnesium alloys and magnesium-based metal matrix composites[J]. Corrosion Science,1995,37(11).

DOI: 10.1016/0010-938x(95)00078-x

[7] Ruiyue Zhang,Shu Cai,Guohua Xu,Huan Zhao,Yan Li, Xuexin Wang, Kai Huang, Mengguo Ren, Xiaodong Wu. Crack self-healing of phytic acid conversion coating on AZ31 magnesium alloy by heat treatment and the corrosion resistance[J]. Applied Surface Science,2014,313.

DOI: 10.1016/j.apsusc.2014.06.104

[8] Jialei Zhang,Changdong Gu,Yueyu Tong,Wei Yan,Jiangping Tu. A Smart Superhydrophobic Coating on AZ31B Magnesium Alloy with Self‐Healing Effect[J]. Advanced Materials Interfaces, 2016, 3(14).

DOI: 10.1002/admi.201500694