scholarly journals Calcium Doped Flash-PEO Coatings for Corrosion Protection of Mg Alloy

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 916 ◽  
Author(s):  
Ewa Wierzbicka ◽  
Borja Pillado ◽  
Marta Mohedano ◽  
Raul Arrabal ◽  
Endzhe Matykina
Keyword(s):  
Salt Spray ◽  
Neutral Salt ◽  
Corrosion Performance ◽  
Full System ◽  
System Protection ◽  
Epoxy Primer ◽  
Plasma Electrolytic ◽  
Peo Coatings ◽  
Hydrolysis Of

This study demonstrates a significant improvement of the corrosion resistance of an AZ31B magnesium alloy achieved by the application of 1 μm-thin coatings generated by an environmentally friendly flash plasma electrolytic oxidation (FPEO) process in Ca-containing electrolytes. Two compounds with different solubility, calcium oxide (CaO) or calcium glycerophosphate (CaGlyP), were used as sources of Ca in the electrolyte. Very short durations (20–45 s) of the FPEO process were employed with the aim of limiting the energy consumption. The corrosion performance of the developed coatings was compared with that of a commercial conversion coating (CC) of similar thickness. The viability of the coatings in a full system protection approach, consisting of FPEO combined with an inhibitor-free epoxy primer, was verified in neutral salt spray and paint adhesion tests. The superior corrosion performance of the FPEO_CaGlyP coating, both as a stand-alone coating and as a full system, was attributed to the formation of a greater complexity of Ca2+ bonds with SiO2 and PO43− species within the MgO ceramic network during the in situ incorporation of Ca into the coating from a double chelated electrolyte and the resultant difficulties with the hydrolysis of such a network. The deterioration of the FPEO_CaGlyP coating during immersion was found over ten times slower compared with Ca-free flash-PEO coating.

scholarly journals Design and Multidimensional Screening of Flash-PEO Coatings for Mg in Comparison to Commercial Chromium(VI) Conversion Coating

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 337
Author(s):  
Ewa Wierzbicka ◽  
Marta Mohedano ◽  
Endzhe Matykina ◽  
Raul Arrabal
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Protection ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Conversion Coating ◽  
Neutral Salt ◽  
Chromium Vi ◽  
Alkaline Electrolytes ◽  
Az31b Alloy ◽  
Plasma Electrolytic

REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) regulations demand for an expedient discovery of a Cr(VI)-free alternative corrosion protection for light alloys even though the green alternatives might never be as cheap as current harmful technologies. In the present work, flash- plasma electrolytic oxidation coatings (FPEO) with the process duration < 90 s are developed on AZ31B alloy in varied mixtures of silicate-, phosphate-, aluminate-, and fluoride-based alkaline electrolytes implementing current density and voltage limits. The overall evaluation of the coatings’ anticorrosion performance (electrochemical impedance spectroscopy (EIS), neutral salt spray test (NSST), paintability) shows that from nine optimized FPEO recipes, two (based on phosphate, fluoride, and aluminate or silicate mixtures) are found to be an adequate substitute for commercially used Cr(VI)-based conversion coating (CCC). The FPEO coatings with the best corrosion resistance consume a very low amount of energy (~1 kW h m−2 µm−1). It is also found that the lower the energy consumption of the FPEO process, the better the corrosion resistance of the resultant coating. The superb corrosion protection and a solid environmentally friendly outlook of PEO-based corrosion protection technology may facilitate the economic justification for industrial end-users of the current-consuming process as a replacement of the electroless CCC process.

scholarly journals Ultrasonic Sensors-Assisted Corrosion Studies on Surface Coated AlSi9Cu3 Alloy Die Castings

Coatings ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 85
Author(s):  
Yuh-Chung Hu ◽  
Senthil Kumaran Selvaraj ◽  
Manivannan Subramanian ◽  
Kathiravan Srinivasan ◽  
Srinivasan Narayanan
Keyword(s):  
Corrosion Resistance ◽  
Die Casting ◽  
Pure Aluminum ◽  
Salt Spray ◽  
Salt Spray Test ◽  
Al Alloy ◽  
Neutral Salt ◽  
Powder Coatings ◽  
Acrylic Paint ◽  
Epoxy Primer

A novel phenomenon known as Industry X.0 is becoming extremely popular for digitizing and reinventing business organizations through the adaption of rapid and dynamic technological, innovational, and organizational changes for attaining the profitable revenue. This work investigates the die-casted commercially pure aluminum alloyed with 9% silicon and 3% copper (AlSi9Cu3) that is produced through the gravity die casting process. Further, the degradation of surface coating on die-casted AlSi9Cu3 alloy was explored. The acrylic paint electrodeposition (ED) coat, 2-coat polyester without primer and 3-coat polyester with epoxy primer powder coatings were used in this study. Moreover, the 3.5 wt.% of sodium chloride (3.5 wt.% of NaCl) test solution was used for electrochemical and salt spray test and the tools used to assess electrochemical properties were electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and neutral salt spray test (NSS). The microstructure of AlSi9Cu3 after corrosion exposure was investigated; also, the microstructure of coated and uncoated AlSi9Cu3 samples was analyzed by SEM microscopy after corrosion exposure. Besides, the electrochemical studies were also carried out on the Al alloy die casting. It was found that acrylic paint ED coatings exhibited higher corrosion resistance than 2-coat polyester without primer & 3-coat polyester with epoxy primer powder coatings. Acrylic paint ED coating showed higher corrosion resistance in AC and a lower value in DC and 3-coat polyester with epoxy primer powder coating displayed higher corrosion resistance in DC and a lower value in AC.

Corrosion performance of a corrosion-resistant rail steel in the simulated subsea tunnel environment

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Qi Zhang ◽  
Min Zhu ◽  
Feng Cai ◽  
Man Liu ◽  
Xue Su ◽  
...  
Keyword(s):  
High Speed ◽  
Rail Steel ◽  
Salt Spray ◽  
Neutral Salt ◽  
Corrosion Performance ◽  
X Ray Diffraction ◽  
High Speed Rail ◽  
Corrosion Resistant ◽  
Electrochemical Tests ◽  
Subsea Tunnel

Abstract The corrosion performance of a newly developed corrosion-resistant rail steel (U68CuCr) was investigated and compared with that of a normally used high-speed rail steel (U71MnG) by neutral salt spray tests, electrochemical tests, X-ray diffraction analyses, and the scanning vibrating electrode technique. It was found that the weight loss and corrosion rate of U68CuCr were lower than those of U71MnG under the same corrosion conditions. In addition, due to the influence of alloying elements (copper and chromium) in U68CuCr, the rust layer was thicker and denser, resulting in a stronger protective effect. Moreover, U68CuCr had a higher corrosion potential in electrochemical tests. Finally, the dynamic corrosion process of U68CuCr in 2.2% NaCl solution mainly followed a lateral extension of corrosion. Therefore, the corrosion resistance of U68CuCr was better than that of U71MnG in the subsea tunnel environment.

Research on the Anti- Corrosion Performance of Two Hot-Dip Coatings

2012 ◽  
Vol 598 ◽  
pp. 520-523
Author(s):  
Zhi Min Cao ◽  
Guo Xin Li ◽  
Hui Lian ◽  
Da Wei Hu
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Salt Spray ◽  
Element Composition ◽  
The Other ◽  
Neutral Salt ◽  
Reaction Products ◽  
Corrosion Performance ◽  
Productive Process ◽  
Scanning Electron

Samples covered two kinds of hot-dip coatings were purchased and placed in neutral salt spray to study the anti-corrosion performance. The results showed that one sample was eroded more seriously than the other. The reasons were analyzed through surface morphology and the reaction products of the hot-dip coatings by scanning electron microscope and element composition. The results showed that might be the fractures developed of the corroded sample during the productive process that made O2 and solution contact with the substrate.

New Passivating Method to Galvanized Zn Coatings on Steel Substrate

2010 ◽  
Vol 163-167 ◽  
pp. 4555-4558 ◽  
Author(s):  
Yun Ying Fan ◽  
Ye Hua Jiang ◽  
Rong Zhou
Keyword(s):  
Corrosion Resistance ◽  
Steel Substrate ◽  
Environmental Awareness ◽  
Salt Spray ◽  
Operating Conditions ◽  
Neutral Salt ◽  
Corrosion Performance ◽  
Solution Composition ◽  
Passivation Time

As the increasing environmental awareness, to explore no-chromium passivation technique on galvanized Zn coatings becomes one of the most urgent affair. In this paper, one kind of silicate passivation technics was invented and by which method silicate conversion film on galvanized Zn coatings with satisfactory property was got. It is found that solution composition and operating conditions of passivation affect the property of conversion film markedly, and the optimal technics is: Na2SiO3 20 g/L, H2SO4 5 mL/L, HNO3 5 mL/L, H2O2 10 ml/L, pH 2.0, passivation time 20 s, temperature 25°C. The corrosion resistance of galvanized Zn coatings with different passivated method, including no passivated, Cr(VI) passivated, Cr(III) passivated and silicate passivated, were investigated by NSS test (5% Neutral Salt Spray). The silicate conversion film can keep no rust for 72 h and obviously shows the best property. All the results show that silicate passivation can provide galvanized Zn coatings superior anti-corrosion performance, so this new technics can replace the conventional chromate passivation technology to avoid the pollution of chromium and has a wider application in future.

Characterization of a Chromium-Free Passivation Coating on Hot Dip Al-Zn Allay Coated Steel Sheets

2013 ◽  
Vol 634-638 ◽  
pp. 2931-2934
Author(s):  
Ping Yuan
Keyword(s):  
Salt Spray ◽  
Optical Emission ◽  
Acrylic Resin ◽  
Organic Coating ◽  
Neutral Salt ◽  
Coated Steel ◽  
Corrosion Performance ◽  
Steel Sheets ◽  
Coated Steel Sheet ◽  
Passivation Coating

The hot dip Al-Zn alloy coated steel sheet was passivated with chromium-free passivation solution which adopted the molybdate and acrylic resin as the main film-forming substances. The surface morphology and corrosion performance of the coating were studied experimentally by using glow discharge optical emission spectroscopy(GD-OES), scanning electron microscopy(SEM) and energy-dispersive X-ray spectroscopy(EDS), polarization curves and the neutral salt spray test. The GD-OES and SEM results show that the molybdate-containing thin organic coating is deposited on the substrate compactly and homogeneously without obvious tiny cracks. The test results of corrosion performance show that the corrosion potential and current density of the passive films decrease obviously in comparison with those of the substrate, and the corrosion resistance of the coating is comparable with that of the chromate passivation coating.

Anti-Corrosion Performance of the Hot-Dip Coating Containing Zn-Al-Mg-Ce

2013 ◽  
Vol 423-426 ◽  
pp. 173-176 ◽  
Author(s):  
Guo Xin Li ◽  
Dong Yang ◽  
Yi Liang Peng ◽  
Wei Tong Yue
Keyword(s):  
Weight Loss ◽  
Loss Rate ◽  
Salt Spray ◽  
Dip Coating ◽  
Neutral Salt ◽  
Congruent Melting ◽  
Corrosion Performance ◽  
Weight Loss Rate ◽  
Salt Spray Testing ◽  
Scanning Electron

The hot-dip coatings containing Zn-Al-Mg-Ce were prepared through congruent melting. The anti-corrosion performance of the coatings was researched using the weight loss rate by the neutral salt spray testing. The reasons of the effects of the elements Al, Mg, Ce on the anti-corrosion performance promoting were researched through the analysis of Scanning Electron Microscope and the polarization curves. The results showed that Al, Mg, Ce embedded in the Zn matrix uniformly and the protective effect for the steel was enhanced by the electrochemical action.

Influence of Silane on Corrosion Performance of Silane-Modified Acrylate Interpenetrating Polymer Network Coating on Magnesium Alloy AZ31

2011 ◽  
Vol 686 ◽  
pp. 186-191
Author(s):  
Rong Chang Zeng ◽  
Chen Lan Liu ◽  
Ling Hong Kong ◽  
Hong Zhi Cui
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Salt Spray ◽  
Polymer Network ◽  
Az31 Alloy ◽  
Interpenetrating Polymer Network ◽  
Neutral Salt ◽  
Corrosion Performance ◽  
Alloy Az31 ◽  
Magnesium Alloy Az31

The possibility that various silane treatments may enhance the corrosion resistance of a magnesium alloy AZ31 with silane-modified acrylate interpenetrating polymer network (IPN) coating has been investigated. Potentiodynamic electrochemical tests and neutral salt spray test were applied to evaluate the corrosion performance of the alloy. The results show that silane film improves corrosion resistance of the AZ31 alloy with and without IPN coating. The silane-modified IPN coatings improved more than 4 orders of magnitude of the corrosion resistance of the substrate.

scholarly journals Effect of Pulse Current Mode on Microstructure, Composition and Corrosion Performance of the Coatings Produced by Plasma Electrolytic Oxidation on AZ31 Mg Alloy

Coatings ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 688 ◽  
Author(s):  
Maryam Rahmati ◽  
Keyvan Raeissi ◽  
Mohammad Reza Toroghinejad ◽  
Amin Hakimizad ◽  
Monica Santamaria
Keyword(s):  
Plasma Electrolytic Oxidation ◽  
Low Frequency ◽  
Current Mode ◽  
Mg Alloy ◽  
Corrosion Performance ◽  
Micro Cracks ◽  
Az31 Mg Alloy ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
Peo Coatings

Plasma electrolytic oxidation (PEO) coatings were grown on AZ31 Mg alloy in a silicate-based electrolyte containing KF using unipolar and bipolar (usual and soft-sparking) waveforms. The coatings were dual-layered consisting of MgO, MgF2 and Mg2SiO4 phases. Surface morphology of the coatings was a net-like (scaffold) containing a micro-pores network, micro-cracks and granules of oxide compounds. Deep pores were observed in the coating produced by unipolar and usual bipolar waveforms. The soft-sparking eliminated the deep pores and produced the lowest porosity in the coatings. It was found that the corrosion performance of the coatings evaluated using EIS in 3.5 wt. % NaCl solution is mostly determined by the inner layer resistance, because of its higher compactness. After 4 days of immersion, the inner layer resistances were almost the same for all coatings. However, the coatings produced by unipolar and usual bipolar waveforms showed sharp decays in inner layer resistances after 1 week and even the barrier effect of outer layer was lost for the unipolar-produced coating after 3 weeks. The low-frequency inductive loops appeared after a 3-week immersion for all coatings indicated that the substrate was under local corrosion attack. However, both coatings produced by soft-sparking waveforms provided the highest corrosion performance.

scholarly journals Wear and Corrosion Resistance of Plasma Electrolytic Oxidation Coatings on 6061 Al Alloy in Electrolytes with Aluminate and Phosphate

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4037
Author(s):  
Zhenjun Peng ◽  
Hui Xu ◽  
Siqin Liu ◽  
Yuming Qi ◽  
Jun Liang
Keyword(s):  
Corrosion Resistance ◽  
Plasma Electrolytic Oxidation ◽  
Salt Spray ◽  
P Element ◽  
Alumina Coating ◽  
Al Alloy ◽  
Wear Properties ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
Peo Coatings

Phosphate and aluminate electrolytes were used to prepare plasma electrolytic oxidation (PEO) coatings on 6061 aluminum alloy. The surface and cross-section microstructure, element distribution, and phase composition of the PEO coatings were characterized by SEM, EDS, XPS, and XRD. The friction and wear properties were evaluated by pin-on-disk sliding tests under dry conditions. The corrosion resistance of PEO coatings was investigated by electrochemical corrosion and salt spray tests in acidic environments. It was found that the PEO coatings prepared from both phosphate and aluminate electrolytes were mainly composed of α-Al2O3 and γ-Al2O3. The results demonstrate that a bi-layer coating is formed in the phosphate electrolyte, and a single-layered dense alumina coating with a hardness of 1300 HV is realizable in the aluminate electrolyte. The aluminate PEO coating had a lower wear rate than the phosphate PEO coating. However, the phosphate PEO coating showed a better corrosion resistance in acidic environment, which is mainly attributed to the presence of an amorphous P element at the substrate/coating interface.

Sign in / Sign up

Export Citation Format

Share Document