Corrosion performance of zinc coated steel in seawater environment

Considering the continuous exploitation of marine resources, it is very important to study the anticorrosion performance and durability of zinc coated streel （ZCS） because its increasing use as reinforcements in seawater. Tafel polarization curves and linear polarization curves combined with electrochemical impedance spectroscopy （EIS） were employed to evaluate the corrosion performance of ZCS at Qingdao test station during long-term immersion in seawater. The results indicated that the corrosion rate of the ZCS increased obviously with immersion time in seawater. The corrosion products that formed on the zinc coated steel were loose and porous, and were mainly composed of Zn5（OH）8C12, Zn5（OH）6（CO3）2, and ZnO. Pitting corrosion occurred on the steel surface in neutral seawater, and the rate of ZCS corrosion decreased with increasing pH.

The Influence of Microscopic Fungi on Chromated Galvanized Zinc Coatings

A solution containing Cr(VI), Cr(NO3)3 and its complex with an organic acid as well as several commercial solutions containing Cr(III) complexes with an organic acid and additionally CO2+, F-, SO42- ions were used for the studies. Results of the studies obtained in the following commercial solutions: Likonda 2AT, Cr(NO3)3 + malonic acid;Likonda 3Cr5 and Likonda 3CrMC are discussed. Steel coated with chromated Zn coatings was contaminated by some microscopic fungi. The variety of fungi on chromated plates diminished, however the propagules of fungi did not disappear completely. The Likonda 3Cr5 solution diminishes fungi contamination on chromated steel most effectively. In water used to rinse the surface of chromated plates the number of fungi propagules was detected to be higher as compared to that on the plate surface. The least quantity of fungi propagules was detected in water used to rinse plates coated in the Likonda 3Cr5 solution. The main part of fungi detected on chromated plates treated in the Likonda 3Cr5 solution were the fungi of Cladosporium species (C.herbarum, C.cladosporioides). The latter species also dominated on chromated plates coated with zinc and treated with the other solution. It should be mentioned, that on these plates chromated in this solution, Actinomycetes of the Streptomyces group were abundant. After comparison of surfaces of the plates treated in four solutions it has been determined that the surface of the plates treated in the Likonda 3Cr5 passivation solution and exposed to modelling conditions changed least of all. It has been noticed that on the subject studied white porous rust accumulates, the intensity of this process on the surface studied determines both the probability of corrosion and the resistance of the used safety means to the external factors.

Electrode degradation mechanism during resistance spot welding of zinc coated steel using Cu-TiB_2 electrodes

The TiB2 dispersion-reinforced copper-matrix composite used as electrode material in resistance spot welding of zinc coated steels was studied. The service life of the composite electrode reaches （7700） welds, which is 4 times that of the conventional Cu-Cr-Zr electrode. Little gross deformation is observed on the composite （electrodes） because of the higher thermal strength; therefore, it is believed that wear is the only mechanism for the composite （electrode） deterioration. However, both wear and plastic deformation are responsible for the large increase in the tip diameter of the Cu-Cr-Zr electrodes. Moreover, the large deformation of the Cu-Cr-Zr electrodes may contribute to the increased wear rate of the tips.

Effect of Some Plating Variables on Zinc Coated Low Carbon Steel Substrates

This work examined the effect of plating variables on zinc coated low carbon steel substrates. The electrodeposition of steel substrates was carried out in zinc electrolyte bath. Time, voltage, distance from the anode to the cathode and the immersion depth served as plating variables. The results showed that weight gained increases as the plating time increases for the constant depth of immersion while the weight gained per unit time by varying immersion depth is irregular. Also, the study demonstrated that sample plated for 20 minutes;20cm from the anode, 45cm depth of immersion at 0.8V exhibited the best plating properties with homogeneity of diffuse plating efficiency.

Joint Performance for Laser Cutting-welding of Zinc-coated Tailored Blanks

The process of laser bull welding of zinc-coated steel（SGCD3 and WLZn）blanks was presented.whose edges were prepared by laser cutting.The properties of the butt joints.such as tensile strength.bending,stamping.weld shape,and corrosion-resisant were tested.The experiments of laser cutting and welding were carried ont on a custom-made system designed.which is a set of equipment for wide sheet butt welding based on a laser cutting-welding combination process.The experiments proved the technological feasibility of laser butt welding for thin zinc coated steel sheets whose edges were prepared by laser cutting on the same equipment.

Growth mechanism for zinc coatings deposited by vacuum thermal evaporation

The vacuum thermal evaporation technique was used to simultaneously deposit zinc coatings onto interstitial free steel plates and single-crystal silicon wafers in a high vacuum environment.The effect of substrate temperature on the mor-phology and crystal orientation of zinc coatings was investigated.When the substrate temperature was 25 and 50℃,the zinc crystallites were plate-like and grew under a particular angle to the substrate surface.After the substrate was heated to 100℃,the zinc crystallites were regular hexagonal and arranged almost parallel to the substrate surface.In addition,observation of pure zinc coatings with different thicknesses showed that the growth of zinc coating was mainly in the Volmer-Weber mode.When the process parameters were appropriate,the zinc coating was composed of closely arranged columnar crystallites,and the crystallites grew preferentially along[0001]direction.

Growth and corrosion resistance of molybdate modified zinc phosphate conversion coatings on hot-dip galvanized steel

The modified zinc phosphate conversion coatings(ZPC) were formed on hot-dip galvanized(HDG) steel when 1.0 g/L sodium molybdate were added in a traditional zinc phosphate solution. The growth performance and corrosion resistance of the modified ZPC were investigated by SEM, open circuit potential(OCP), mass gain, potentiodynamic polarization and electrochemical impedance spectroscopy(EIS) measurements and compared with those of the traditional ZPC. The results show that if sodium molybdate is added in a traditional zinc phosphate solution, the nucleation of zinc phosphate crystals is increased obviously; zinc phosphate crystals are changed from bulky acicular to fine flake and a more compact ZPC is obtained. Moreover, the mass gain and coverage of the modified ZPC are also boosted. The corrosion resistance of ZPC is increased with an increase in coverage, and thus the corrosion protection ability of the modified ZPC for HDG steel is more outstanding than that of the traditional ZPC.

Dynamic simulation of resistance spot welding of zinc-coated steels

A model was developed to simulate the temperature distribution and nugget formation during resistance spot welding （ RS1V） of zinc-coated steels. It employs a coupled thermal-electrical-mechanical analysis simulating the dynamic RSW process. Temperature-dependent thermal-electrical-mechanical material properties were considered including contact-resistance. The contact area was determined from a coupled thermal-mechanical analysis. A layer of transition elements was used to represent the change of contact area by killing or activating elements. The heat generation and temperature field were computed in a coupled thermal-electrical model. All these analyses were solved using the commercial finite element method （FEM） based on ANSYS code, and some advanced functions were used by writing a paragraph of codes by the authors. Compared with the results from only coupled thermal-electrical model in which contact area was uniform during the whole process, the result matches better to the experimental results.

Corrosion behavior of sintered zinc-aluminum coating in NaCl solution

Sintered zinc aluminum coating (SZAC) was prepared using zinc flakes, aluminum flakes and CrO 3 as main raw materials. The corrosion behavior of SZAC in 3.5%NaCl solution was studied by means of SEM, EDS, EIS and so on. Results indicate that aluminum corroded in advance of zinc to produce speculate or spherical substances, which attaches to SZAC and adds mass to it. Corrosion production passivates metal powders in SZAC, causes E corr of SZAC to increase gradually, and causes the arising of the third time constant in EIS, which corresponds to the insulation of corrosion production.

Carbon-coated manganese dioxide nanoparticles and their enhanced electrochemical properties for zinc-ion battery applications

In this study, we report the cost-effective and simple synthesis of carbon-coated α-MnOnanoparticles(α-MnO@C) for use as cathodes of aqueous zinc-ion batteries(ZIBs) for the first time. α-MnO@C was prepared via a gel formation, using maleic acid(CHO) as the carbon source, followed by annealing at low temperature of 270 °C. A uniform carbon network among the α-MnOnanoparticles was observed by transmission electron microscopy. When tested in a zinc cell, the α-MnO@C exhibited a high initial discharge capacity of 272 m Ah/g under 66 m A/g current density compared to 213 m Ah/g, at the same current density, displayed by the pristine sample. Further, α-MnO@C demonstrated superior cycleability compared to the pristine samples. This study may pave the way for the utilizing carbon-coated MnOelectrodes for aqueous ZIB applications and thereby contribute to realizing high performance eco-friendly batteries.

Properties of Al/Conductive Coating/α-PbO2-CeO2-TiO2/β-PbO2-WC-ZrO2 Composite Anode for Zinc Electrowinning

The properties of Al/conductive coating/α-PbO2-CeO2-TiO2/β-PbO2-WC-ZrO2 composite anode for zinc electrowinning were investigated. The electrochemical performance was studied by Tafel polarization curves（Tafel）, electrochemical impedance spectroscopy（EIS） and corrosion rate obtained in an acidic zinc sulfate electrolyte solution. Scanning electron microscopy（SEM）, X-ray diffraction（XRD）, and energy dispersive X-ray spectroscopy（EDXS） were used to observe the microstructural features of coating. Anodes of Al/conductive coating/α-PbO2-CeO2-TiO2/β-PbO2, Al/conductive coating/α-PbO2-CeO2-TiO2/β-PbO2-WC, Al/conductive coating/α-PbO2-CeO2-TiO2/β-PbO2-ZrO2, and Pb-1%Ag anodes were also researched. The results indicated that the Al/conductive coating/α-PbO2-CeO2-TiO2/β-PbO2-WC-ZrO2 showed the best catalytic activity and corrosion resistant performance; the intensity of diffraction peak exhibited the highest value as well as a new PbWO4 phase; the content of WC and ZrO2 in coating showed the highest value as well as the finest grain size.

STUDIES OF LOW-CONCENTRATION CHROMATE PASSIVE FILM FOR ZINC-BASED ALLOY COATED STEEL WIRES

The corrosion resistance of a low concentration chromate passive film for zinc based alloy coated steel wires was assessed by salt spray and electrochemical corrosion tests. XPS and AES analyses showed that the composition of such chromate passive film was S 5 5, Na 3 4, C 11 8, Ti 7 9, O 41 6, Cr 13 7, Zn 16 0.

Effect of Rare Earth on the Corrosion-Resisting Performance of Zinc-Based Alloy Coatings

The corrosion behavior of coatings of pure zinc and Zn-Al,Zn-Al-RE alloys in NaCl solu- tions was studied by salt-spray experiments,even corrosion experiments and electrochemical measurements of bi-directional polarization curves and a.c.impedance in weak polarization region consistent regularities were obtained by these different methods,viz.,the corrosion resistance of Zn could be enhanced by alloying it with Al,and particularly with Al-RE.The causes of enhancement of corrosion resistance by RE were also discussed.

Effect of heat diffusion on properties of zinc-aluminum coating on AZ91D magnesium alloys

A protecting zinc and aluminum coating on the surface of AZ91D magnesium alloys was obtained by thermal spraying to improve the corrosion and wear resistance performances. In order to enhance the combination between magnesium alloy matrix and zinc and aluminum coating, the sample was heat-treated at 300℃for 2 h, then, the cross-section patterns, XRD pattern, micro-hardness, wear and corrosion resistance abilities were researched. The results indicate that the interface between the coating and substrate is metallurgical bond, and a transitional fusion layer is formed by diffusion. The micro-scale abrasion test and polarization test in 3% NaCl solution show that the diffusion-treated specimen has better wear and corrosion resistance performances in comparison with the undiffusion-treated and substrate magnesium alloys; in addition, it has relatively higher micro-hardness than the undiffusion-treated magnesium alloys.

Microstructure and Performances of Nanocrystalline Zinc-nickel Alloy Coatings

Nanocrystalline zinc-nickel alloy coatings were deposited from an alkaline zincate bath contained an organic additive that can reduce polarization and a complexing agent. SEM and TEM observations and XRD analysis were performed to examine the microstructure and phase composition of the coatings. The nickel content in deposits is 12.0-14.7% and the coating is consisted of single nanocrystalline y-phase structure (Ni5Zn2i), with grain average grain size about 15nm. The nanocrystalline zinc-nickel alloy coatings have better corrosion resistance, less bnttleness and higher microhardness than the conventional zinc coatings.

Dual Bath Electrodeposition of Alternate Multilayer Coatings of Zinc and Nickel Deposits

The synthesis of zinc and nickel alternate multilayer coatings produced by successive deposition from dual baths containing a revised zinc sulphate electrolyte and a new developed nickel bath has been investigated. Smooth and uniform zinc-nickel compositionally modulated multilayered (CMM) coatings with different multilayer configurations were obtained. The surface and cross-sectional morphologies of samples were examined using scanning electron microscopy (SEM). Cross-sectional morphology showed the layered structure of the coatings clearly.

CeO_2/Zn NANOCOMPOSITE COATING BY ELECTRODEPOSITION

The nanocomposite coating is obtained by electrochemical deposition of the zinc plating solution with ceria nanoparticles (mean diameter 30 nm). The effect of ceria nanoparticles on the electrodeposited zinc coating is stu died by weight loss test, inductively copuled plasma quantometer (ICP), scanning electron microscopy (SEM) and X ray diffraction (XRD), respectively. It is found that under the same electrodeposition conditions, the corrosion resistance of the nanocomposite coating increases obviously while that of the micron composite coating only improves slightly; The ceria content of the nanocomposite coating is more than that of the micron composite coating. Ceria nanoparticles modify the surface morphology and crystal structure of the zinc matrix in correlation with the increase of corrosion resistance.

Morphology and texture of high speed galvanized coatings on interstitial free steel sheet

The morphology and texture of zinc coatings deposited on interstitial free （IF） steel sheets were investigated by means of scanning electron microscopy （SEM） and orientation distribution function. It was shown that the microstructure of the coatings consisted of thin hexagonal platelets tilted with respect to the substrate surface. Zinc coatings exhibited low angle pyramidal {11.5} nonfiber texture component resulting from epitaxial growth via two-dimensional （2D） nucleation. The 2D nucleation was attributed to severe zinc hydroxide adsorption on the substrate surface during the nucleation stage, which can inhibit three-dimensional （3D） nucleation and promote nonfiber texture. The pyramidal texture was beneficial for plastic deformation of zinc coatings because a significant amount of resolved shear stress can be obtained when the uniaxial stress is applied.

CeO2/Zn NANOCOMPOSITE COATING BY ELECTRODEPOSITION

The nanocomposite coating is obtained by electrochemical deposition of the zinc plating solution with ceria nanoparticles (mean diameter 30 nm). The effect of ceria nanoparticles on the electrodeposited zinc coating is stu died by weight loss test, inductively copuled plasma quantometer (ICP), scanning electron microscopy (SEM) and X ray diffraction (XRD), respectively. It is found that under the same electrodeposition conditions, the corrosion resistance of the nanocomposite coating increases obviously while that of the micron composite coating only improves slightly; The ceria content of the nanocomposite coating is more than that of the micron composite coating. Ceria nanoparticles modify the surface morphology and crystal structure of the zinc matrix in correlation with the increase of corrosion resistance.