THE INFLUENCE OF COMPOSITION AND TEMPERATURE OF BATH ANDAFTER-TREATMENT 0N COLORATION IN COLORING HOT DIPGALVANIZATION

The 08 Al steel sheets were hot dip ped into Zn - Mn bath with 0 1 % Mn and 0 2 % Mn at600 ～420 ℃ bath tem perature , and then w ere treated in different w ays . The after - treat ments include cooling in the air at room tem perature directly , holding at the upper part of thehot dip galvanizing furnace for 60 s an d then holding at 510 ±10 ℃for 90 s . The results in dicated that blue , yellow , and purple , w hose coloration varied with the co m position an d thetem perature of bath and the w ays of after - treat ment . Finally , the mechanism of coloredzinc coating w as discussed .

Effect of Zinc Galvanization on the Microstructure and Fracture Behavior of Low and Medium Carbon Structural Steels

Microstructure and fracture behavior of ASTM 572 Grade 65 steels used for wind tower applications have been studied. Steels of two carbon level chemistries designed for this grade were used in the study. Fracture toughness of the steels was studied using 3-point bend test on samples coated with zinc and not coated with zinc. Lower carbon steel showed higher resistance to fracture than medium carbon steel after zinc galvanization. SEM study suggests that zinc and zinc bath additives that migrated to crack tips are responsible for the loss in ductility. The phenomenon of Liquid Metal Embrittlement (LME) is suggested to have taken place. Zinc bath additives traced at crack zones are suggested to have migrated at the zinc galvanizing temperatures.

Effect of pyrite content on chalcopyrite flotation under different regrinding conditions

This study aimed to investigate the effect of varying pyrite(Py)content on copper(Cu)in the presence of different regrinding conditions,which were altered using different types of grinding media:iron,ceramic balls,and their mixture,followed by flotation in the cleaner stage.The flotation performance of rough Cu concentrate can be improved by changing the regrinding conditions based on the Py content.Scanning electron microscopy,X-ray spectrometry,ethylenediaminetetraacetic acid disodium salt extraction,and X-ray photoelectron spectroscopy studies illustrated that when the Py content was high,the use of iron media in regrinding promoted the generation of hydrophilic Fe OOH on the surface of Py and improved the Cu grade.The ceramic medium with a low Py content prevented excessive Fe OOH from covering the surface of chalcopyrite(Cpy).Electrochemical studies further showed that the galvanic corrosion current of Cpy-Py increased with the addition of Py and became stronger with the participation of iron media.

Electrochemistry and DFT study of galvanic interaction on the surface of monoclinic pyrrhotite(001)and galena(100)

The electrochemical interaction between galena and monoclinic pyrrhotite was investigated to examine its impact on the physical and chemical properties of the mineral micro-surface.This investigation employed techniques such as electrochemistry,metal ion stripping,X-ray photoelectron spectroscopy,and quantum chemistry.The electrochemical test results demonstrate that the galena surface in the electro-couple system exhibits a lower electrostatic potential and higher electrochemical activity compared to the monoclinic pyrrhotite surface,rendering it more susceptible to oxidation dissolution.Monoclinic pyrrhotite significantly amplifies the corrosion rate of the galena surface.Mulliken charge population calculations indicate that electrons are consistently transferred from galena to monoclinic pyrrhotite,with the number of electron transfers on the mineral surface increasing as the interaction distance decreases.The analysis of state density revealed a shift in the surface state density of galena towards lower energy levels,resulting in decreased reactivity and increased difficulty for the reagent to adsorb onto the mineral surface.Conversely,monoclinic pyrrhotite exhibited an opposite trend.The X-ray photoelectron spectroscopy(XPS)test results indicate that galvanic interaction leads to the formation of hydrophilic substances,PbS_(x)O_(y) and Pb(OH)_(2),on the surface of galena.Additionally,the surface of monoclinic pyrrhotite not only adsorbs Pb^(2+)but also undergoes S^(0) formation,thereby augmenting its hydrophobic nature.

Galvanic corrosion behavior of AZ91D alloy/45 steel couple under magnetic field

Galvanic corrosion behavior of AZ91D alloy/45 steel couple in 3.5 wt.%NaCl solution under 0,0.2 and 0.4 T magnetic field were studied by microstructure observation,immersion test and electrochemical measurement.The mixed potential theory was used to estimate the galvanic current density and the mixed potential of the galvanic corrosion between AZ91D alloy and 45 steel.The results indicated that magnetic field could accelerate the corrosion of AZ91D alloy,and impede the corrosion process of 45 steel.The effect of magnetic field on corrosion sensibility and corrosion rate of these two alloys increased as the intensity rising.The galvanic corrosion rate of the couple was accelerated by magnetic field.With the magnetic field intensity rising,the galvanic corrosion sensibility and corrosion rate of the couple increased.The effects of magnetic field on the galvanic corrosion performance of the couple and the corrosion behavior of AZ91D alloy and 45 steel were due to the appearance of field gradient force and magnetohydrodynamic(MHD)force.The mixed potential theory has a certain accuracy to estimate the Ecouple and icouple values in this work.

Improvement of corrosion resistance of PEO coated dissimilar Ti/Mg0.6Ca couple

With the growing demand for weight reduction,the application of joint lightweight structural materials is increasing.Magnesium alloys feature low density,high specific strength and good formability,offering significant advantages for fuel efficiency and load capacity.Combined with Ti,a dissimilar Ti/Mg composite material provides great flexibility combining the properties of each material.However,because of the great differences in chemical and electrochemical properties between Mg and Ti,it is imperative to address the galvanic corrosion problem of such dissimilar Ti/Mg components.This work presents an investigation of the PEO processing of sintered Ti/Mg0.6Ca couples,aiming to improve the corrosion resistance of such dissimilar alloy combinations using a phosphate-aluminate electrolyte.The results show that uniform and continuous coatings can be formed on the dissimilar Ti/Mg0.6Ca couple.The coating mainly contains MgO and MgAl_(2)O_(4)on the Mg0.6Ca side,and Al_(2)TiO_(5)is the dominant phase on the Ti side.The work also took advantage of synchrotron X-ray computed tomography(CT)scanning to achieve 3D reconstruction of the coating morphology,which can be a fast method to assess the porosity and compactness of the coating and further predict the coating corrosion resistance.The coating effectively improved the corrosion resistance of the dissimilar Ti/Mg0.6Ca couple.

Mg-Ti hybrid joints:Surface modification,corrosion studies and 3D-pore investigation using synchrotron-based microtomography

A new direction toward the future of orthopedic implants is to combine biodegradable Mg alloys with permanent Ti to produce selectively biodegradable hybrid joints for advanced tissue engineering.However,the strong galvanic corrosion between Mg and Ti is a major issue to be considered.This work aims to explore plasma electrolytic oxidation(PEO)as a single-step coating treatment to allow for an acceptable degradation behavior of MgTi hybrid systems.To this end,MgTi hybrid joints were produced through the heat treatment of Mg-0.6Ca and commercially pure Ti specimens at 640°C for 8 h.A single-step PEO treatment was then employed to create a protective layer on the surface of hybrid couples.Even though the scanning electron microscopy(SEM)images showed only a porosity of 6%and 12%within the PEO layers on single Mg and MgTi couples,3D investigation of the synchrotron-based microtomography data demonstrated a porosity of 18%and 30%with a considerable number of interconnected pores.According to the electrochemical impedance spectroscopy measurements,the impedance modulus at all frequencies on coated MgTi coupled specimens was lower than that on the coated single Mg-0.6Ca and pure Ti.However,the application of PEO treatment significantly decreased the strong galvanic degradation of Mg-0.6Ca in contact with Ti.The results of hydrogen evolution tests revealed that PEO-treated MgTi couples showed a similar degradation behavior as the single alloy during the first day of immersion.

Investigation and improvement of tiny spot defects on hot-dip galvanized automotive steel sheets

The causes of tiny spot defects on the surface of hot-dip galvanized automotive steel sheets were studied using scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS),and effective control measures were introduced.The results show that rubbing against the top roller after galvanizing is easy due to the local thickness of tiny spot defect location coating;therefore,the surface morphology is different from the normal part.Three kinds of defects,namely zinc slag,small slivers,and pitting,are likely to cause local thickening of the coating after galvanizing,leading to the formation of tiny spots.Therefore,resolving the three types of defects can effectively control the generation of tiny spot defects.Among them,due to the hereditary nature of the small sliver defect,focusing on its control and supervision is necessary.

ToF-SIMS characterization of a bare-spot defect in a hot-dip galvanized boron-added steel sheet

To determine the root cause of a bare-spot defect in a hot-dip galvanized boron-added steel sheet,we performed metallurgical characterizations using time-of-flight secondary ion mass spectrometry(ToF-SIMS)in addition to glow discharge optical emission spectrometry,field-emission scanning electron microscopy(FE-SEM),and energy dispersive spectroscopy.Mn and B enrichments on the steel surface in the bare-spot area were detected through various methods.FE-SEM revealed external oxide nodules and zinc droplets,which indicated poor wettability.ToF-SIMS further revealed considerably more detailed lateral and depth distributions of Mn,B,and Al.The formation of external Mn-B compound oxides on the steel surface prior to hot dipping,which substantially deteriorated the wettability and prevented the formation of a Fe_(2)Al_(5)inhibition layer,resulted in the formation of a bare-spot defect.ToF-SIMS mapping of Al ion proved that a slight reaction still occurred between the dissolved Al in the molten zinc bath and steel substrate,although no evident Fe_(2)Al_(5)inhibition layer formed in the bare-spot area.

Galvanic Skin Response—Extinction Biofeedback Training for Psychogenic Abdominal Pain: A Validation Protocol

Abdominal and pelvic pain of psychogenic origin is a widespread, disabling, difficult to identify, and often inadequately treated medical condition. This condition is often associated with poor quality of life due to high pain interference with daily activities. Cognitive behavioral psychological therapy and neuromodulation with biofeedback are validated therapies for the treatment of this condition. Aim of the present research work is the validation of a therapeutic protocol that involves the use of both techniques in combination. 20 patients diagnosed with psychogenic abdominal pain, of both sexes, aged between 18 and 60 years who had not benefited from pharmacological therapies were enrolled. 10 patients were randomly assigned to the control group (psychological treatment only), another 10 patients were assigned to the study group (neuromodulation with biofeedback-Galvanic skin response-extinction in combination with psychological therapy). For both groups, the pain score, interference of pain with daily living activities, pain relief, and the share of anxiety associated with the pain condition were evaluated (pre- and post-treatment). The patients who underwent the combined treatment achieved statistically significant better scores than patients in the control group, respectively −4.9 ± 0.9 vs −1.0 ± 0.4 for Pain;−5.1 ± 1.1 vs −0.9 ± 0.3 for Interference with life;−7.2 ± 3.7 vs −2.2 ± 2.1 for HAMA;4.6 ± 1.2 vs 1.1 ± 0.6 for Relief.

Galvanic corrosion behavior of copper/titanium galvanic couple in artificial seawater

The corrosion behaviors of copper and copper/titanium galvanic couple （GC） in seawater were studied by electrochemical impedance spectroscopy （EIS） and electrochemical noise （EN） techniques in conjunction with scanning electron microscopy （SEM） method. The results show that the corrosion process of copper in seawater can be divided into two stages, in which corrosion resistance and SE show the same evolution trend of initial increase and subsequent decrease, while SG changes oppositely. However, the ensemble corrosion process of copper/titanium GC in seawater includes three stages, in which corrosion resistance and SE show the evolution features of initial decrease with a subsequently increase, and the final decrease again;while SG changes oppositely. The potential difference between copper and titanium in their galvanic couple can accelerate the initiation of pitting corrosion of copper, and both the minimum and maximum corrosion potentials of copper/titanium GC are much more positive than those of pure copper.

Effects of reflowing temperature and time on alloy layer of tinplate and its electrochemical behavior in 3.5%NaCl solution

Effects of reflowing temperature and time on the alloy layer of tinplate and its electrochemical behavior in 3.5%NaCl solution were investigated by electrochemical measurements and surface characterization.It is found that the amount of alloy layer increases with the increase of reflowing temperature and time.Then the corrosion potential of detinned tinplate shifts positively and the corrosion rate decreases.After being coupled with tin,the detinned tinplate acts as cathode and tin acts as anode initially.However,after being exposed for some time,the potential shifts of both detinned tinplate and tin reverse the polarity of the coupling system.The galvanic current density decreases with the increase of reflowing temperature and time.

Effects of galvanic interaction between galena and pyrite on their flotation in the presence of butyl xanthate

The effects of galvanic interaction between galena and pyrite on their flotation and electrochemical characters were studied by electrochemical,adsorption,flotation and FTIR techniques,respectively.Electrochemical tests indicate that galena is electrochemically more active than pyrite and serves as an anode in galvanic combination with pyrite.The galvanic current density from a mixture of galena and pyrite is 4 times as high as the self corrosion current density of galena,which indicates that the corrosion rate of galena is accelerated.Adsorption tests show that the adsorption of butyl xanthate on galena surface is enhanced,and affected by a combination of pyrite-galena mixtures and conditioning time.Compared with individual mineral particles,galvanic interaction reduces the floatability difference between galena and pyrite.The flotation recovery of galena decreases while that of pyrite increases when two minerals are mixed together due to the influence of galvanic interaction on the formation of hydrophilic/hydrophobic product.The FTIR results show that the formation of dixanthogen on pyrite surface is depressed due to the galvanic interaction.

Design of TRIP Steel With High Welding and Galvanizing Performance in Light of Thermodynamics and Kinetics

A new type of transformation induced plasticity （TRIP） steel with not only high strength and high ductility but also superior welding and galvanizing properties was designed and developed recently. Low carbon and low silicon content were preliminarily selected with the aim of meeting the requirements of superior quality in both welding and galvanizing. Phosphorus was chosen as one of the alloying elements, because it could reduce carbon activity in cementite and increase the stability of austenite. In addition, the possibility of phosphorus segregating at grain boundary was also discussed by thermodynamics as well as kinetics. Phase diagram was estimated at high temperature and the composition of the steel was then selected in the hyperperitectic range to avoid problems, which might occur in sheet steel continuous casting. Phase diagram in the inter.critical temperature was estimated for the steel to obtain the starting temperature of fast cooling. For understanding the minimum rate of fast cooling, pearlite growth kinetics was calculated with self-developed diffusion coefficients of elements in grain boundary. Overaging temperature was determined through the calculation of To temperature by both equilibrium and para-equilibrium assumptions, which was different from the current determination, which is only based on an equilibrium estimation.

Triangular Au-Ag framework nanostructures prepared by multi-stage replacement and their spectral properties

Triangular Au-Ag framework nanostructures （TFN） were synthesized via a multi-step galvanic replacement reaction （MGRR） of single-crystalline triangular silver nanoplates in a chlorauric acid （HAuCl4） solution at room temperature. The morphological, compositional, and crystal structural changes involved with reaction steps were analyzed by using transmission electron microscopy（TEM）, energy-dispersive X-ray spectrometry （EDX）, and X-ray diffraction. TEM combined with EDX and selected area electron diffraction confirmed the replacement of Ag with Au. The in-plane dipolar surface plasmon resonance （SPR） absorption band of the Ag nanoplates locating initially at around 700 nm gradually redshifted to 1 100 nm via a multi-stage replacement manner after 7 stages. The adding amount of HAuCl4 per stage influenced the average redshift value per stage, thus enabled a fine tuning of the in-plane dipolar band. A proposed formation mechanism of the original Ag nanoplates developing pores while growing Au nanoparticles covering this underlying structure at more reaction steps was confirmed by exploiting surface-enhanced Raman scattering （SERS）.

Activities of binary baths with 1% solute as standard states

The relationships of activities with 1% solute as standard state and mass fraction of solute, and hot dip temperature, were given on the base of Miedema’s model, Tanaka expression, some basic thermodynamic relationships; and discussion was carried out on Zn Mn and Zn Ti binary alloys by calculation, in which varied colors can be achieved onthe hot dip steel sheets. The results indicate that the activity of solute shows positive deviation relative to Henry’s law for both Zn Mn and Zn Ti binary dilute solution. The degree of deviation increases with increasing solute and decreases with increasing bath temperature. As the solution is very dilute solution ( w (Mn)≤40% for Zn Mn alloy, w (Ti)≤8% for Zn Ti alloy), the two binary baths can all be treated as ideal dilute solutions. [

High activity of a Pt decorated Ni/C nanocatalyst for hydrogen oxidation

The Pt decorated Ni/C nanocatalysts were prepared for hydrogen oxidation reaction（HOR） in fuel cell.By regulating the contents of Pt and Ni in the catalyst,both the composition and the structure affected the electrochemical catalytic characteristics of the Pt-Ni/C catalysts.When the Pt mass content was 3.1% percent and that of Ni was 13.9% percent,the Pt-Ni/C-3 catalyst exhibited a larger electrochemically active surface area and a higher exchange current density toward HOR than those of pure supported platinum sample.Our study demonstrates a feasible approach for designing the more efficient catalysts with lower content of noble metal for HOR in fuel cell.

Galvanic反应原位制备多金属氢氧化物用于OER催化

采用镍氨和钴氨为电解液电沉积金属钴镍,提高材料的比表面积和导电性,再通过Galvanic反应快速合成了金属钴镍复合钴镍铁氢氧化物(CoNi/CoNiFe H)催化剂用于OER催化,采用XRD、SEM、XPS对材料的结构、形貌进行了表征,并研究了其电化学性能。结果表明:在1 M KOH溶液中,电流密度为10 mA·cm^(-2)时,过电位仅有250 mV,Tafel斜率为29 mV·dec^(-1),且具有良好的稳定性。这为制备廉价的多金属复合材料用于高效OER催化提供了新的方法。

Growth and corrosion behavior of rare earth film on hot-dip galvanized steel

Hot-dip galvanized(HDG)steel sheets were treated for 30 s?24 h by the rare earth aqueous solution containing 20 g/L Ce(NO3)3·6H2O,and the growth behavior and corrosion resistance of the rare earth film were investigated by SEM,EDS,AES and NSS.The results reveal that the rare earth film becomes thick while the mass gain of the samples does not distinctly change due to the zinc dissolution with the increase of treatment time.The film grows up more quickly and is apt to cracking in the vicinity of zinc grain boundaries,and eventually the film partly warps and flakes off with increasing film thickness.The NSS results show that the corrosion resistance of the film is dominated by both the film thickness and the cracks.With increasing treatment time,the corrosion resistance of the film increases within 1 h due to the increased film thickness and decreases after 1 h because the cracking and flaking off gradually become dominant factor.

Rare earth and silane as chromate replacers for corrosion protection on galvanized steel

The present work aimed at using rare earth lanthanum salt and trimethoxy（viny）silance as chromate substitutes for galvanized steel passivation, in contrast to zinc coating samples treated with chromate.The corrosion resistance was assessed by electrochemical impedance spectroscopy（EIS） and neutral salt spray tests（NSS）.Scanning electron microscopy（SEM） was used to characterize the sample surfaces.The organic coating adhesion on the panel was also investigated via varnishes-cross cut tests.The results indicated that rare earth and silane two-step treatment gave more effective anticorrosion performance than Cr, which also provided good paint adhesion.The coating formation mechanism was also discussed.