Relationship between heat treatment and corrosion behaviour of Mg-3.0%Nd-0.4%Zr magnesium alloy

The corrosion behaviour of Mg-3.0Nd-0.4Zr (NK30) magnesium alloy was investigated in as-cast (F), solution treated (T4) and peak-aged (T6) conditions in 5% NaCl solution by immersion tests and electrochemical measurements. The results of immersion test show that NK30 alloy exhibits better corrosion resistance in F condition than it does in the other two conditions due to the more compact corrosion film formed on alloy in F condition. The potentiodynamic polarization curves show that the overpotential of cathodic hydrogen evolution reaction on NK30-F is much higher than that on NK30-T4 and NK30-T6. The corrosion potentials of NK30 increase in the following order: F<T4<T6. The results of electrochemical impedance spectroscopy (EIS) also confirm that the corrosion film of NK30-F plays a more protective role than that of NK30-T4 and NK30-T6.

Electrochemical corrosion of Sn-0.75Cu solder joints in NaCl solution

The corrosion behaviors of Sn-0.75Cu solder and Sn-0.75Cu/Cu joint in 3.5% NaCl（mass fraction） solution were studied by potentiodynamic polarization test and leaching measurement.The polarization curves indicated that the corrosion rate of Sn-0.75Cu solder was lower than that of Sn-0.75Cu/Cu joint.The morphology observation and phase composition analysis on the corroded product at each interesting potential suggested that Sn3O（OH）2Cl2 formed on the surface of Sn-0.75Cu solder at active dissolution stage.As the potential increased from active/passive transition stage,all the surface of Sn-0.75Cu solder was covered by the Sn3O（OH）2Cl2 and some pits appeared after the polarization test.Compared to the Sn-0.75Cu solder alloy,much more Sn3O（OH）2Cl2 formed at active dissolution stage and the pits with bigger size were observed after polarization test for the Sn-0.75Cu/Cu solder joints.The leaching test confirmed that the faster electrochemical corrosion rate resulted in the larger amount of Sn released from the Sn-0.75Cu/Cu solder joints.

Electrochemical behaviour of Ti alloys containing Mo and Ta as β-stabilizer elements for dental application

Corrosion behaviour of the studied Ti12Mo and Ti60Ta alloys with the same Mo equivalent values （12%, mass fraction） together with the currently used metallic biomaterials Cp-Ti were investigated for dental applications. The electrochemical properties of the samples were examined using electrochemical techniques： such as open-circuit potential, potentiodynamic polarization curves and electrochemical impedance spectroscopy （EIS）, in two electrochemical media of artificial saliva and fluoridated artificial saliva （0.1%fluoride ions, F-） at 37 °C. Fluoride is commonly included in toothpastes, odontological gels and dental rinses to prevent dental caries and relieve dental sensitivity. The passive behaviour for all the titanium samples is observed for both solutions. The Ti60Ta alloy appears to possess superior corrosion resistance than the Ti12Mo and Cp-Ti in both electrochemical media.

Effect of Ti content on corrosion behavior of Cu-Ti alloys in 3.5% NaCl solution

The corrosion behavior of the Cu-Ti alloys with different Ti contents in 3.5%(mass fraction)NaCl solution was investigated using electrochemical measurements,immersion tests,mass loss measurements and SEM observation.The results show that Ti dissolved in the Cu matrix changes the corrosion process of the alloys.Pure Cu sample exhibits a typical active–passive-transpassive corrosion behavior.The anodic polarization current densities of the Cu-Ti alloys steadily increase with increasing applied potential,indicating that active dissolution of copper proceeds due to the potential difference in the galvanic coupling of Cu and Ti.The increase of Ti content decreases the corrosion resistance of the Cu-Ti alloys.

Effect of Schiff base as corrosion inhibitor on AZ31 magnesium alloy in hydrochloric acid solution

Schiff base derived from the condensation reaction of analar grade 1-amino-2-naphthol 4-sulphonic acid with cinnamaldehyde was prepared under microwave condition.The Schiff base was analysed by infrared spectroscopy.This Schiff base as a corrosion inhibitor of AZ31 magnesium alloy in 0.05 mol/L HCl solution was studied.The inhibition effect of the Schifif base compound（4Z）-4-（3-phenyl allylidene amino）-3-hydroxy naphthalene-1-sulfonic acid（AC） on AZ31 magnesium alloy corrosion was studied using mass loss,potentiodynamic polarization technique,electrochemical impedance spectroscopy methods.The potentiodynamic polarization curve shows that Schiff base AC inhibits both anodic and cathodic reactions at all concentration,which indicates it is a mixed type inhibitor.EIS results indicate that as the additive concentration is increased,the polarization resistance increases whereas double-layer capacitance decreases.The adsorption of AC on the AZ31 magnesium alloy surface in 0.05 mol/L HCl obeys the Langmuir adsorption isotherm.

Environmentally assisted cracking resistance of Al-Cu-Li alloy AA2195 using slow strain rate test in 3.5% NaCl solution

The general corrosion and environmental cracking resistances of Al-Cu-Li alloy AA2195 were investigated in 3.5% NaCl environment and compared with those of another high strength alloy AA2219. The general corrosion resistance of these alloys was examined using immersion corrosion and potentiodynamic polarization tests, while the stress corrosion cracking （SCC） resistance was evaluated by slow strain rate test （SSRT） method. The tested samples were further characterized by SEM-EDS and optical profilometry to study the change in corrosion morphology, elemental content and depth of corrosion attack. The reduction in ductility was used as a parameter to evaluate the SCC susceptibility of the alloys. The results indicated that the corrosion resistance of AA2195 alloy was better than that of AA2219 alloy as it exhibited lower corrosion rate, along with lower pit depth and density. However, the SCC index （εNaCl/εair） measured was greater than 0.90, indicating good environmental cracking resistance of both the alloys. Detailed fractography of the failed samples under SEM？EDS, in general, revealed a typical ductile cracking morphology for both the alloys.

Oxidation of chalcopyrite in air-equilibrated acidic solution: Inhibition with phenacyl derivatives

The effects of 4-(2-hydroxyphenyl)-2-(morpholin-4-yl)-1,3-thiazole(Pr02), 1-(3,5-dibromo-2-hydroxyphenyl)-1-oxoethan-2-yl-N,N-diethyldithiocarbamate(Pr04) and 1-(5-bromo-2-hydroxy-3-methylphenyl)-1-oxoethan-2-yl-Oethyl xanthate(Pr06) on the aqueous oxidation of chalcopyrite(CuFeS2) in air-equilibrated solution at a temperature of 25 ℃ and a pH of 2.5 were studied. The effects were investigated by using potentiodynamic polarization, electrochemical impedance spectroscopy(EIS), scanning electron microscopy coupled with energy dispersive X-ray(SEM/EDX) analysis, aqueous batch experiments, Fourier transform infrared(FTIR) spectroscopy, Raman scattering and quantum chemical calculations. It is found that the anodic current densities decrease in the order of EtOH > Pr02 > Pr04 > Pr06. These results, along with those of the EIS measurements, show that Pr02, Pr04 and Pr06 are effective anodic inhibitors of chalcopyrite aqueous oxidation. Both Raman scattering and FTIR spectroscopy indicate that the elemental sulfur, polysulfide and ferric oxyhydroxides that form on the surface of the mineral are not responsible when it comes to the aqueous oxidation inhibition of chalcopyrite. Quantum chemical calculations show that the adsorption of the tested compounds on the chalcopyrite surface is energetically favorable and so, it can explain the inhibiting effects that were observed.

Inhibition effect of a synthesized N,N′-bis(2-hydroxybenzaldehyde)-1,3-propandiimine on corrosion of mild steel in HCl

The corrosion inhibition of mild steel in 1 mol/L HC1 by N, N＇-bis （2-hydroxybenzaldehyde）- 1, 3-propandiimine （2-HBP） has been investigated by using potentiodynamic polarization, electrochemical impedance spectroscopy （EIS） and chronoamperometry measurements. The experimental results suggest that this compound is an excellent corrosion inhibitor for mild steel and the inhibition efficiency increases with the increase in inhibitor concentration. Polarization curves reveal that this organic compound is a mixed type inhibitor. The effect of temperature on the corrosion behavior of mild steel with the addition of the Schiff base was studied in the temperature range from 25 ℃ to 65℃. The experimentally obtained adsorption isotherms follow the Langmuir equation. Activation and thermodynamic adsorption parameters such as Ea, △H, △S,Kads and AG,ds were calculated by the corrosion currents at different temperatures and using the adsorption isotherm. The morphology of mild steel surface in the absence and presence of 2-HBP was examined by atomic force microscope （AFM） images.

Intergranular Corrosion of AISI 304 Heat Treated at 800℃ Varying Range Times

Austenitic stainless steels, when exposed to welding conditions or aging for length of service, it＇s observed the formation of numerous deleterious phases, such as several kinds of carbides type MC, M6C, M7C3, M23C6, and intermetallic secondary phases （sigma, chi, laves）, which cause the process of intergranular corrosion. The aim of this work was verifying the formation of the types of carbides and/or intermetallic phases existing in the stainless AISI 304 at 800 ℃, varying the timing of heat treatment between 30, 360 and 1,440 min. The optical microscopy analysis revealed the predominant formation of the carbide type M23C6. The results of DL-EPR （double loop electrochemical potentiokinetic reactivation） tests showed a gradual increase in the precipitation of this carbide with the increase of treatment time. The potentiodynamic polarization showed that the precipitation of this carbide reduce the formation of the Cr2O3 passive layer, suggesting that the precipitate carbide to be predominantly of the Cr23C6 type.

Influence of chloride ion concentration on initial corrosion of AZ63 magnesium alloy

The initial corrosion behavior of AZ63 magnesium alloy was investigated in 1,3,5 and 7 wt.%NaCl solutions by means of corrosion potential,linear polarization,electrochemical impedance spectroscopy,and polarization measurements,during exposure in the corrosion media.Results show that the increase in chloride concentration provokes an increase in the corrosion rate.Based on the obtained kinetics parameters the mechanisms of anodic dissolution and hydrogen evolution reactions were discussed,and kinetic models were proposed.It is concluded that anodic dissolution proceeds under Temkin conditions and hydrogen evolution reaction depends on the surface coverage of Mg(OH);species.

Electrochemical characterization of Ti12Mo5Ta alloys in contact with saline medium

The electrochemical behaviours of unrecrystallized and recrystallized Ti12Mo5Ta alloys were compared with those of the unrecrystallized Ti12 Mo alloy and commercial pure titanium（cp-Ti）. Experiments were carried out using physiological 0.9% NaCl solution（pH 2.3） at 37 °C. Very low passive current densities（in order of 10-6 A/cm2） were obtained from the anodic polarization curves, indicating high resistances of all samples in acidified 0.9% Na Cl solution. Scanning electron microscopy（SEM） was employed to observe the surface morphology and all sample surfaces were identically corroded, no pitting, cracks, or other defects appeared on the sample surfaces after anodic potentiodynamic polarization tests. Equivalent circuit was used for modeling the electrochemical impedance spectroscopy（EIS） data, in order to characterize the sample surface and better understand the effect of Mo and Ta addition on the cp-Ti and the effect of recrystallization. The EIS results confirm that all titanium samples exhibit passivity in physiological 0.9% NaCl solution（pH 2.3） at open circuit potential（polarization resistance is around 105 Ω·cm2）. The corrosion resistance of these samples in physiological 0.9% NaCl solution（pH 2.3） at 37 °C is in the following order of recrystallized Ti12Mo5Ta〉 unrecrystallized Ti12Mo5Ta 〉 unrecrystallized Ti12Mo 〉 cp-Ti.

Autocatalytic deposition of copper from modified electrolytes and its characteristics

The electroless deposition process of copper plating consisting of TEA and EDTA as complexing agents,paraformaldehyde as reducing agent,and 2-mercaptobenzothiozole as stabilizer and gelatin and animal glue as additives was investigated.The stability of the electroless copper solution was monitored by measuring the absorbance of the solution with a UV-Visible spectrophotometer and the solution was quite stable up to 15 h.The adhesion of copper films on mild steel foil was assessed by standard bend test and exhibited good adhesion.The XRD results indicate that the copper films have a(111) texture.Moreover,the additives suppress the predominant(111) plane crystal growth and increase the rate of(220) texture crystal growth.The crystal size of the copper films was calculated using the Scherrer formula from the predominant peak.SEM and AFM studies reveal that these two additives modify the crystal structure,grain size and surface morphology of the copper films.The cyclic voltammetry studies reveal that the additives are adsorbed on the electrode surface and inhibit the rate of deposition.Potentiodynamic polarization and electrochemical impedance studies reveal that the deposits produced in the presence of additives display higher corrosion resistance.

Inhibition effect of 2-amino-5-ethyl-1,3,4-thiadiazole on corrosion behaviour of austenitic stainless steel type 304 in dilute HCl solution

The corrosion inhibition of type 304 austenitic stainless steel by 2-amino-5-ethyl-1, 3, 4-thiadiazole(TTD) compound and the electrochemical behaviour in dilute HCl solution were investigated through potentiodynamic polarization test, mass loss techniques and potential measurements. The results show that the organic derivative is highly effective with a maximum inhibition efficiency of 70.22% from mass loss analysis, while 74.2% is obtained from polarization tests. Observation of the scanning electron micrographs shows the absence of corrosion products due to electrochemical influence of TTD on the surface morphology of the steel. X-ray diffractometry reveals the absence of phase compounds and complexes on the steel samples after exposure. TTD adsorption on the steel surface obeys the Langmuir, Frumkin and Freundlich adsorption isotherms. Corrosion thermodynamic calculations reveal the inhibition mechanism occurs through chemisorption process and results from statistical analysis depict the strong influence of inhibitor concentration on the electrochemical performance of the TTD.

Preparation High-Temperature Behavior of Conversion Coating of Alumina Film on FeCrAI （Ce） Stainless Steel

FeCrAI （Ce） stainless steel was functionalized by a conversion treatment in order to allow alumina by diffusion coatings with strong interfacial bonding. The very porous conversion coating produced in a pack aluminization technique had excellent adhesion and was conductive enough to permit conditions favorable for the precipitation of alumina oxyhydroxide during aluminum diffusion coatings. In this work, the bed was prepared as a mixture of A1, NH4C1 and A1203. In the high-activity bed were heat-treated at 1,173 K in an atmosphere made up of team with subsequent air-cooling. The effect of the bed content on the coating was examined. With the high-activity, the desired Fe2Al5 was formed as the outermost coating layer. The coating presented chemical composition gradients suitable for strong adhesion. The improvement of the thermal oxidation behaviour was studied at 1,373 K. Two different aqueous environments, which are （1） NaC1 and （2） H2SO4, are employed for using the technique of potentiodynamic polarization curve. The obtained experimental electrochemical parameters （Ecorr, Jcorr etc,） were used to compare the corrosion resistance of the tested steel state complemented by MEB （electronic scanning microscopy） in combination with dispersive analysis X in energy （EDS） or X ray diffraction indicated that the elements concentration maximum was located in the vicinity of the interface especially in the FeCrAI （Ce） coated by spherical A1203 powder. These results an discussed in terms of an addition effect on the development of the microstructure of oxide films.

W-Ni-Cu和W-Ni-Fe合金的腐蚀性能（英文）

高比重钨合金是一种具有高密度,高强度和良好的耐腐蚀性等特性的复合材料。采用沉浸试验和电化学试验对2种钨合金(90%W-6%Ni-4%Cu和95%W-3.5%Ni-1.5%Fe)的腐蚀性能进行了研究。结果表明,当W-Ni-Cu合金发生电偶腐蚀时,W相首先遭到腐蚀;而在W-Ni-Fe合金中,粘结相会先发生腐蚀。动电位极化测量结果表明,pH值对高比重钨合金腐蚀速率有显著影响,与酸性环境相比较,合金在中性溶液中腐蚀速率较低。根据SEM和EDX的结果分析了合金成分的溶解以及腐蚀产物的生成等腐蚀机理。

“Petal effect”-inspired superhydrophobic and highly adhesive coating on magnesium with enhanced corrosion resistance and biocompatibility

With properties of complete degradation and favorable mechanical behavior, Mg and its alloys are regarded as the next generation medical metal materials. However, fast degradation and poor surface biocompatibility hinder their clinical applications. Inspired by the ＂petal effect＂, we successfully constructed a superhydrophobic and highly adhesive coating on pure Mg via a simple hydrothermal treatment in a solution containing sodium oleate. The superhydrophobicity of the fabricated coating results from its flake-like micro-nanostructure and the low-surface-energy oleate group. Water droplet on the superhydrophobic coating cannot roll off even when the sample is turned upside down, owing to the sealed air-pockets and the van der Waals’ attraction at the solidliquid interface, indicating a highly adhesive force. The chemical and mechanical stability of the superhydrophobic coating were measured. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements suggest enhanced corrosion resistance of the as-prepared sample.Furthermore, cell cytotoxicity, migration and adhesion data of human umbilical vein endothelial cells（HUVECs） reveal an improved cytocompatibility of the modified surface. Finally,hemolysis assay and platelet adhesion assay suggest an improved hemocompatibility. It is believed that the facile and low-cost method can expand the new application of superhydrophobic surface with highly adhesive on Mg in biomedical fields.

Corrosion resistance and cytocompatibility of Ti-20Zr-10Nb-4Ta alloy surface modified by a focused fiber laser

The corrosion resistance and cytocompatibility of Ti-20 Zr-10 Nb-4 Ta（TZNT） alloy modified by surface laser treatment were investigated. The scanning electron microscopy（SEM） measurements indicated that laser treatment on TZNT alloy generated groove morphologies with the width of^40 μm and the depth of ~10 μm on the surface. The water contact angles along the groove direction decreased by 51%compared with that of the untreated alloy. The laser treatment promoted the oxidation of metallic Ti, Zr and Nb and produced more stable oxides on surface. The corrosion potential increased by 50% and corrosion current density decreased by72% compared with that of the untreated alloy in the anodic polarization test for the alloy in Hank’s solution at 37°C. This indicated the improvement of the corrosion resistance by laser treatment. The cytotoxicity testing results showed that the laser-treated TZNT alloy performed similar MC3 T3-E1 cell viability compared with the untreated alloy. The cells displayed oriented growth along the groove direction due to the increased hydrophilicity. This novel material may be a new candidate in orthopedics and dentistry implantations fields.