Microstructure, Growth Kinetics, and Corrosion Resistance of Hot-Dip Galvanized Zn-5% Al Coatings

CORROSION ◽  
1991 ◽  
Vol 47 (7) ◽  
pp. 536-541 ◽  
Author(s):  
L. A. Rocha ◽  
M. A. Barbosa
Keyword(s):  
Growth Kinetics ◽  
Immersion Time ◽  
Anodic Polarization ◽  
Corrosion Potential ◽  
Surface Enrichment ◽  
Molten Bath ◽  
Good Adhesion ◽  
Electrochemical Tests ◽  
Deaerated Solution ◽  
Preferential Dissolution

Abstract Several characteristics of Zn-5% A1 coatings—namely microstructure, growth kinetics, and electrochemical behavior—have been studied. A ZnCl2-based flux for the production of Zn-5% Al coatings by a dry hot-dip galvanizing process, developed in this work, produced coatings with good adhesion and without bare spots. The coating thickness is practically independent of the immersion time (between 1 and 600 seconds). The formation of an intermetallic compound on the surface of the steel during the first moments of contact with the molten bath is responsible for this behavior. Electrochemical tests in a 0.1 M NaCl deaerated solution have shown that the corrosion potential is ca. 400 mV anodic in relation to the corrosion potential of the steel and that preferential dissolution of zinc occurs during anodic polarization, resulting in a surface enrichment of aluminum.

scholarly journals Ultrasonic Treatment Induced Fluoride Conversion Coating without Pores for High Corrosion Resistance of Mg Alloy

Coatings ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 996
Author(s):  
Sheng Li ◽  
Laihua Yi ◽  
Xiongxiang Zhu ◽  
Tongfang Liu
Keyword(s):  
Corrosion Resistance ◽  
Ultrasonic Treatment ◽  
Corrosion Potential ◽  
Ph Value ◽  
Corrosion Current ◽  
Mg Alloy ◽  
Chemical Compositions ◽  
Good Adhesion ◽  
Fluoride Treatment ◽  
Electrochemical Tests

Fluoride conversion (MgF2) coating with facile preparation and good adhesion is promising to protect Mg alloy, but defects of pores in the coating lead to limited corrosion resistance. In this study, a compact and dense MgF2 coating was prepared by the combination of fluoride treatment and ultrasonic treatment. The ultrasonically treated MgF2 coating showed a compact and dense structure without pores at the frequency of 28 kHz. The chemical compositions of the coating were mainly composed of F and Mg elements. The corrosion potential of the ultrasonically treated Mg alloy shifted towards the noble direction in the electrochemical tests. The corrosion current density decreased due to the protectiveness of MgF2 coating without defects of pores or cracks. During immersion tests for 24 h, the ultrasonically treated Mg alloy exhibited the lowest H2 evolution (0.32 mL/cm2) and pH value (7.3), which confirmed the enhanced anti-corrosion ability of MgF2 coating. Hence, the ultrasonically treated fluoride coating had great potentials for their use in anti-corrosion applications of Mg alloy.

scholarly journals Zeolites as reservoirs for Ce(III) as passivating ions in anticorrosion paints

2018 ◽  
Vol 36 (3) ◽  
pp. 305-322 ◽  
Author(s):  
Sol Roselli ◽  
Cecilia Deyá ◽  
Mariana Revuelta ◽  
Alejandro R. Di Sarli ◽  
Roberto Romagnoli
Keyword(s):  
Zinc Phosphate ◽  
Corrosion Potential ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Electrochemical Techniques ◽  
Steel Electrode ◽  
Electrochemical Tests ◽  
Second Stage ◽  
Total Pigment ◽  
Anticorrosion Pigment

AbstractThe aim of this paper was to evaluate the performance of two different modified zeolitic minerals as anticorrosion pigments in order to reduce or eliminate zinc phosphate in paints. In the first stage, the selected minerals were characterized and modified with cerium ions to obtain the anticorrosion pigments. Their inhibitive properties were evaluated by means of electrochemical techniques (corrosion potential measurements and polarization curves) employing a steel electrode immersed in the pigments suspensions. In the second stage, solvent-borne paints, with 30% by volume of the anticorrosion pigment, with respect of the total pigment content, were formulated. The performance of the resulting paints was assessed by accelerated (salt spray and humidity chambers) and electrochemical tests (corrosion potential measurements and electrochemical impedance spectroscopy) and compared with that of a control paint with 30% by volume of zinc phosphate. Results obtained in this research suggested that zeolites can be used as carriers for passivating ions in the manufacture of anticorrosion paints with at least reduced zinc phosphate content.

Electrochemical Tests of Corrosion of Magnetic Hard Disks With Overcoats of DLC

2003 ◽  
Author(s):  
Soyoung Jung ◽  
Thomas M. Devine
Keyword(s):  
Anodic Polarization ◽  
Electrochemical Impedance ◽  
Electrochemical Techniques ◽  
Low Frequency ◽  
Quantitative Relationship ◽  
Hard Disks ◽  
Electrochemical Tests ◽  
Magnetic Hard Disks ◽  
Metal Layers ◽  
Dc Polarization

Two electrochemical techniques were used to investigate the corrosion of DLC coated magnetic hard disks: (1) potentiodynamic and potentiostatic anodic polarization and (2) electrochemical impedance spectroscopy. The objective was to determine the ability of DC polarization and AC polarization to detect the presence of porosity in the DLC. The results indicate that anodic polarization at high potentials (≈ +1.0V vs SCE) to cause pitting corrosion of the metal layers underneath the DLC might provide a rapid and quantitative estimate of the amount of porosity in the DLC. Measurement of the low frequency electrochemical impedance at intermediate potentials (≈ +0.5V vs SCE) appears to indicate the presence of porosity but further work is required to establish a quantitative relationship between the amount of porosity and the value of the low frequency impedance.

Preparation, Corrosion and Cytocompatability In Vitro of Fluoride-Coated Mg-Zn-Zr Alloy

2016 ◽  
Vol 852 ◽  
pp. 1293-1299
Author(s):  
Hao Ran Zheng ◽  
Jing Zhang ◽  
Chen You ◽  
Min Fang Chen
Keyword(s):  
Aqueous Solution ◽  
Corrosion Resistance ◽  
Body Fluid ◽  
Immersion Time ◽  
Processing Time ◽  
Corrosion Potential ◽  
Solution Treatment ◽  
Good Biocompatibility ◽  
Zr Alloy

The present investigation was carried out to optimize the hydrogen fluoride (HF) aqueous solution treatment for an Mg-2.5Zn-0.5Zr alloy, in order to improve the corrosion resistance of the material for orthopaedic applications. An MgF2 coating was formed on the surface of Mg-2.5Zn-0.5Zr alloy treated with HF solution. The effect of the HF concentration and processing time on the morphology and electrochemical performance of the MgF2 coating was systematically studied. The results showed that the MgF2 coating became thick gradually with the increase of the concentration of HF solution. However, the pinhole on the surface treated with 40% HF increased significantly. The coating thickness immersed in the same concentration of HF solution increased with immersion time, and cracks formed in the surface after four hours of immersion, resulting in a decrease in the corrosion potential. When the alloy was immersed in the HF solution with a concentration 20% at 37°C for 2h, a uniform and dense fluoride coating was formed, with a thickness of MgF2 layer of about 0.5μm. The corrosion potential of the coated Mg alloy in simulated body fluid (SBF) was 0.28V higher than the uncoated one. In addition, the fluoride-coated showed a good biocompatibility.

Effect of Zn Content on the Microstructure and Corrosion Behaviour of Mg-7Y-0.6Zr Alloy

2013 ◽  
Vol 765 ◽  
pp. 612-617
Author(s):  
Jian Li Wang ◽  
Jian Ping Li ◽  
Ping Wang ◽  
Yong Chun Guo ◽  
Zhong Yang
Keyword(s):  
Corrosion Rate ◽  
Corrosion Potential ◽  
Volume Fraction ◽  
Corrosion Behaviour ◽  
Secondary Phase ◽  
Immersion Test ◽  
Electrochemical Tests ◽  
Method Effect ◽  
Zn Content ◽  
Mould Casting

Mg-7Y-0.6Zr-xZn (x = 0, 0.5, 1.0, 1.5, 2.0, 2.5, wt.%) alloys were prepared by the metal mould casting method. Effect of Zn content on the microstructures and corrosion behaviour were investigated. Results showed that microstructures were refined and volume fraction of secondary phase Mg24(YZn)5 was increased with increasing addition of Zn element. Results of electrochemical tests demonstrated that the corrosion potential of Mg-7Y-0.6Zr alloy was about -1.77 V, and, with addition of 0.5~2.0 wt.% Zn element, corrosion potential moved to more positive values than that of Mg-7Y-0.6Zr alloy. Mg-7Y-0.6Zr-0.5Zn alloy possessed the most positive corrosion potential of -1.53 V. The results of immersion test with different time also indicated that corrosion rate could be decreased by addition of 0.5~2.0 wt.% Zn, and Mg-7Y-0.6Zr-0.5Zn alloy exhibited the lowest corrosion rate.

scholarly journals Corrosion and Wear performances analysis of PVD CrMoN/Cr Coatings

10.30544/640 ◽  
2021 ◽  
Vol 27 (3) ◽  
pp. 397-409
Author(s):  
Kheireddine BOUZID ◽  
Rim LAMARI ◽  
Nasser Eddine BELIARDOUH ◽  
Corrine NOUVEAU ◽  
Barnali Biswas
Keyword(s):  
Sliding Wear ◽  
Room Temperature ◽  
Corrosion Potential ◽  
Adhesive Wear ◽  
Uncoated Sample ◽  
Electrochemical Tests ◽  
Wear And Corrosion ◽  
Disc Configuration ◽  
Wear Tests ◽  
Ball On Disc

Tools coated CrN based alloys are currently used in several industries for machining and manufacturing, but present severe wear, limiting their service life. Seeking an alternative, three CrMoN monolayers (~1µm in thickness) coatings with varying in the Mo percentage content were elaborated using the RF magnetron co-sputtering method. These coatings were evaluated and compared with the alloy currently used (CrN) by electrochemical tests in NaCl solution (stationary and no stationary method) and sliding wear tests (ball-on-disc configuration) performed at room temperature. The results indicate that the samples coated with CrMoN presented better performance against wear and corrosion than the uncoated sample. Among the coatings, the labeled C1 (27 % Mo) showed the best corrosion resistance as it presents a positive corrosion potential Ecorr. However, the best wear resistance (lowest coefficient of friction) was shown by coating labeled C4 (33 % Mo). All of the tested specimens underwent abrasive wear in addition to adhesive wear.

scholarly journals Effect of Er-Rich Precipitates on Microstructure and Electrochemical Behavior of the Al–5Zn–0.03In Alloy

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 131
Author(s):  
Muzhi Yu ◽  
Jin Cui ◽  
Zhichao Tang ◽  
Zinan Shen ◽  
Xiaoyang Chen ◽  
...  
Keyword(s):  
Current Efficiency ◽  
Electrochemical Behavior ◽  
Corrosion Current Density ◽  
Corrosion Potential ◽  
Impedance Spectrum ◽  
Corrosion Current ◽  
Element Composition ◽  
The Self ◽  
Dissolution Reaction ◽  
Preferential Dissolution

The effect of Er-rich precipitates on microstructure and electrochemical behavior of the Al–Zn–In anode alloy is investigated. The results showed that with the increase in Er content, the microstructure was refined, the amount of interdendritic precipitates gradually increased, and the morphology changed from discontinuous to continuous network gradually. With the addition of Er element, the self-corrosion potential of the Al–5Zn–0.03In–xEr alloy moved positively, the self-corrosion current density decreased, and the corrosion resistance increased. When the Er content was less than 1 wt.%, the addition of Er improved the dissolution state of the Al–5Zn–0.03In–xEr alloy, and increased the current efficiency of the Al–5Zn–0.03In–xEr alloy. When the Er content was more than 1 wt.%, the current efficiency was reduced. The major precipitate of the alloy was Al3Er. According to the element composition of Al3Er in the Al–Zn–In–Er alloy, the simulated-segregated-phase alloy was melted to explain the effect of Al3Er segregation on the electrochemical behavior of alloys, and the polarization curve and AC impedance spectrum of the simulated-segregated-phase alloy and the Al–Zn–In alloy were measured. The results showed that Al3Er was an anodic segregation phase in the Al–Zn–In–Er alloy, and the preferential dissolution of the segregation phase would occur in the alloy, but the Al3Er phase itself was passivated in the dissolution process, which inhibited the further activation of the dissolution reaction of the Al–Zn–In–Er alloy to a certain extent.

Characteristics of Inconel 625 Filler Metal Affecting to Weld and Deposited Metal Zones in the Case of Welded to Forged Steel for Piston Crown Material

2014 ◽  
Vol 1004-1005 ◽  
pp. 1114-1119
Author(s):  
Sung Yul Lee ◽  
Kyung Man Moon ◽  
Jong Pil Won ◽  
Jae Hyun Jeong ◽  
Tae Sil Baek
Keyword(s):  
Corrosion Resistance ◽  
Weld Metal ◽  
Base Metal ◽  
Anodic Polarization ◽  
Corrosion Potential ◽  
Filler Metal ◽  
Polarization Curves ◽  
Inconel 625 ◽  
Piston Crown ◽  
Deposited Metal

Recently, wear and corrosion of the engine parts surrounded with combustion chamber is more serious compared to the other parts of the engine due to using of heavy oil of low quality. Therefore, an optimum repair welding for these parts is very important to prolong their lifetime in a economical point of view. In this study, Inconel 625 filler metal was welded with GTAW method in the forged steel which would be generally used with piston crown material. In this case, the mechanical and corrosion properties between weld metal zone (WM) welded to the groove which were artificially made in the base metal and deposited metal zone (DM) only welded by Inconel 625 filler metal on the surface of the base metal were investigated using electrochemical methods, such as measurement of corrosion potential, anodic polarization curves, cyclic voltammogram and impedance etc. in 35% H2SO4 solution. The deposited metal zone exhibited a better corrosion resistance compared to the weld metal zone, furthermore, its corrosion potential was a nobler value rather than that of the weld metal zone. However, the hardness indicated more or less higher value in the weld metal zone. The corrosive products after measurement of anodic polarization curves was hardly observed both in the weld and deposited zones, while, the morphologies of the corroded surfaces exhibited general and pitting corrosion in the weld and deposited metal zones respectively. The fine pearlite microstructure was a little observed in the weld metal zone, moreover, the microstructure of ferrite with elliptical pattern was significantly increased in the deposited metal zone. As a result, it is considered that the amount of Cr, Mo and Ni having a high corrosion resistance diffuse and migrate from the weld metal zone to the base metal zone, thus, the deposited metal zone indicated a better corrosion resistance than the weld metal zone because the amount of Cr, Mo and Ni were much involved in deposited metal zone compared to the weld metal zone.

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