Showing papers in "Materials protection in 2005"

Present and Prospect of Microbial Corrosion Prevention of Concrete

Abstract: Damage of microbial corrosion of concrete was presented,then the corrosion mechanism was introduced,and the measures and problems in microbial corrosion of concrete were described,finally the future development was prospected.

Current Status and Progress of Study on Micro-Arc Oxidation Technology

Abstract: A review was given on the development of micro-arc oxidation technology since its establishing in 1960s, with the power supply, electrolyte, and substrate metals to be focused on. The distribution rules of the compositions and phase structures of the micro-arc oxidation coatings, as well as the influences of current density, oxidation time, voltage, electrolytes, and other factors on the growth and properties of the coatings were summarized. It was pointed out that there still exist some disadvantages in the related theoretical research and production cost control of the micro-arc oxidation technology, though it has a promising application perspective.

Corrosion Resistance of Copper Surface Modified with(3-Mercaptopropyl) Trimethoxysilane in NaOH Solution

Abstract: Self-assembled monolayer film of(3-mercaptopropyl) trimethoxysilane(MPTS) was formed on electropolished surface to improve the corrosion resistance of copper.The structure of MPTS film was studied by using FTIR and SEM,and the inhibition effect of film was evaluated for copper in 0.5 mol/L NaOH solution using electrochemical linear polarization and AC impedance.The effects of deposit time and silane concentration were also discussed.The corrosion resistance of copper is improved markedly owing to the chemical absorption of MPTS on copper,and linear oligomer forms on the surface by cross-linking of Si-O-Si bonds.The higher is MPTS concentration,the more compact is the film.The corrosion potential of copper with MPTS film moves positive 200 mV,the corrosion current decreases an order of magnitude than that of blank copper,and the inhibition efficiency is 86.5%.MPTS monolayer retards the reduction of dissolved oxygen and inhibits the growth of copper oxide in the NaOH solution.

Adsorption of Wastewater Containing Heavy Metal Ions by Modified Fly Ash

Abstract: A modified fly ash absorbent with excellent adsorbability was prepared using the fly ash from a thermal power plant as the major raw materials Thus the fly ash was mixed with a given amount of pyrite cinder and NaCl, stirred and immersed with waste sulfuric acid at 90 ℃ for 25 h, and dried at 300 ℃, to allow the generation of the target modified fly ash The adsorption capability of the modified fly ash to various heavy metal ions was examined under static state condition, with an emphasis being placed on determining the suitable conditions for the removal of the heavy metal ions such as Cr~(6+), Pb~(2+), Cu~(2+), and Cd~(2+) in industrial electroplating wastewater by the modified fly ash The results showed that the adsorption capability of the modified fly ash to heavy metal ions was greatly dependent on the pH value of the wastewater to be treated, and the suitable pH value ranges varied for different metal ions After absorbed by the modified fly ash at room temperature and pH=80, the heavy metal ions in the Cr(VI) containing electroplating wastewater with every individual heavy metal ion content below 50 mg/L was removed at a rate over 975%, and the treated wastewater passed the corresponding national discharge standard

Effect of Crystal Grain Size on Corrosion Resistance of Weathering Steels in Atmosphere

Abstract: The atmospheric corrosion resistance of four types of weathering steels with mean grain sizes of 6, 10, 19 μm, and 60 μm were studied using accelerated industrial atmospheric corrosion test in lab. Thus the steels were subject to dry-wet cyclic immersion tests, and the morphologies and process of the rust layers were analyzed by means of optical metallography, X-ray diffraction, and electrochemical impedance spectroscopy. It was found that during the initial corrosion period when the inner rust layer was not formed, the fine-grained weathering steels had a higher corrosion rate than the coarse-grained one. During the later corrosion period when the inner rust layer had been formed, both the coarse-grained and fine-grained weathering steels had nearly the same corrosion rate. Though grain-refining helped to greatly improve the mechanical properties of the weathering steels, it had little effect on the atmospheric corrosion resistance and the compactness of the rust layers of the weathering steels.

Microstructure and Hardness of Laser Cladding Nickel Based Alloy Doped with WC on Q235 Steel

Abstract: The microstructure and micro hardness of laser cladding Ni based alloy doped with WC on Q235 steel were analyzed using optical microscopy, scanning electron microscopy, micro hardness testing, and electron probe microanalysis Thus efforts were made to determine the optimum content of WC in the laser cladding It was found that no cracking happened in the laser cladding Ni based alloy until the mass fraction of WC surpassed 30% The average hardness of the laser cladding Ni based alloy increased with increasing WC content The WC particulates were completely melted and dissolved in the cladding alloy The solidified phase was mainly composed of dendrite and eutectic, and the cladding showed cell and strip like metastable two phase structure

Typical Engineering Examples for Zinc Aluminum Thermal Spraying Coating on Marine Steel Structures

Abstract: A review is given on the protection of the marine steel structures including offshore platforms, oversea bridges, and marine ships by thermally sprayed zincaluminum coating, based on the summarizing the applications of the thermal spraying technique in various relevant engineering fields world wide.It is pointed out the thermal spraying anticorrosive technology has a short history in China, and its application for the longterm protection of the steel structures in severely corrosive marine environment still remains untouched. Therefore, it is imperative to enhance the research on the longterm corrosion protection of the steel structures working in severely corrosive marine environments making use of thermally sprayed zinc, aluminum, and zincaluminum alloy coatings, so as to speed the development and utilization of the ocean resources. The relevant engineering application examples have indicated that the thermally sprayed aluminum,zinc,and aluminumzinc alloy coatings are mature in providing costeffective corrosion protection for the marine and offshore steel structures.Specifically,the thermally sprayed aluminum coating sealed by some appropriate organic coating has been found to have excellent anticorrosive ability for the steel structures at the splash zone at normal and high temperatures.It is thus suggested to introduce and popularize the spraying zincaluminum coating technique in the protection of the steel structures working in severely corrosive marine environments.

Micro/Nano-Structure and Mechanism of Anti-Sticky Thin Film on Copper Substrate

Abstract: High-performance anti-sticking film was prepared on copper substrate using chemical corrosion method. Thus the mixture of analytically pure HCl, HNO_3 and HF at a certain volume fraction was used as the corrosive liquid to corrode the copper substrate so that a lotus-leaf-like micro-and nano-structure was formed thereon. Then the aqueous solution of 1% fluoroalkyl silane was used to modify the corroded copper surface to allow the generation of the anti-sticking film of super repellence to water and oil after drying in air. The contact angles of water, caster oil, and HTPB on the unmodified copper surface were measured to be 80°, 25°and 50°, respectively; while that on the modified copper surface were 153°, 137°and 142°. The ratio of the air contacting with the liquid droplet in the fine structure of the modified copper surface was calculated to be about 0.93% using the CB equation. The excellent repellence to water and oil of the fluoroalkyl silane anti sticking film was attributed to its micro/nano-structure and low surface energy.

Wastewater Treatment in Sn Pb Alloy Electroplating and Polishing Passivation of Brass

Abstract: The wastewater treatment of Sn Pb alloy electroplating and polishing passivation of brass were harsh, owing to the complex composition, diversity of harmful substances, and fluctuant concentrations of the ingredients to be removed. Thus the titled wastewater after diffluence and well mixing was treated making use of physical chemical and biochemical combination treating processes. At the same time, an automation controlling system integrated with pH/ORP control and compute control was also applied for the treatment of the wastewater. It was found that the discharged water after the treatment met the relevant standard requirement and the process was satisfactory in terms of the industrial running.

Preparation and Oxidation Resistance of Self-Healing Coating for C/C Composite

Abstract: For the aim of extending the application field of C/C composite as high temperature construction material,an oxidation protective coating with self-healing function for C/C composite was prepared,which mainly consisted of SiC and Si-B-Al- Cr-Zr based oxide ceramic.The mean oxidative mass loss of coated samples after isothermal tests in static and dry air from 700 ℃ to 1 000 ℃ is about 2.91×10~(-7)～(9.43)×10~(-6) g/(cm~2·s),the coating has promised oxidation resistance under the temperature of 1 000 ℃.The oxidation rate decreases within 5～6 thermal cycles between 300 ℃ and 1 000 ℃,and then increases after that,the mass loss of coated sample is 19.64% after 10 thermal cycles in 6 hours,the coating has thermal shock resistance in some extent.SiC combined B based ceramic coating can provide low mass loss and oxidation rate for coated C/C composite in long period oxidation and some thermal cycles.

Corrosion Resistance of Zinc Nickel Alloy Plating

Abstract: Zinc plating and (zinc )nickel (16%) alloy plating were prepared on ferrous substrate by electrodepositing in a sulfate bath. The composition of the Zn Ni alloy plating was determined using energy dispersive X ray analysis. The corrosion resistance of the plating was investigated by neutral salt spray (NSS) test, potentiodynamic polarization curve, AC impedance technique, and immersion corrosion test. It was found that the corrosion potential of the Zn Ni alloy plating had a positive shift by 230 mV as compared with that of the pure Zn plating. At the same time, the Zn Ni (16%) alloy plating had excellent corrosion resistance. Namely, the Zn Ni alloy plating had a salt spray resistance of 1 000 h, which was 4.5 times as much as that of the pure Zn plating with the same thickness.

CO_2/H_2S Corrosion Behavior of Tubular Steel P110 at 90 ℃

Abstract: Autoclave test,together with weight loss method,XRD,SEM and EDS,were used to study CO_2/H_2S corrosion behavior of tubular steel P110 in simulated oil well produced water at 90 ℃.The results show that under the test conditions,the corrosion rate of tubular steel P110 is high as(5.126 0) mm/a.The corrosion form is mainly H_2S corrosion(pitting) and the corrosion product is mainly sulfide.

Cr-Ni Alloy Electroplating Technology in Trivalent Chromium Bath and Coating Performance

Abstract: The technological formula and criterion for the chromiumnickel alloy electroplating in a sulfate bath were studied using industrial grade leathertanning agent chromium sulfate and nickel sulfate as the major salts. The influences of cathode current density, pH value, and temperature on the performance of the coating were investigated, while the correlation among the Cr content in the plating and the corrosion resistance and solderability was explored. The corrosion resistance of the CrNi alloy coatings with different compositions was compared by corrosion current measurement. As the results, it was feasible to control the Cr content (mass fraction) in the alloy coating within 10%~50% by properly adjusting the plating parameters. The plating with Cr content below 10% had excellent solderability. The CrNi alloy coating containing 25%~40% Cr had good corrosion resistance, and the coating containing 30% Cr had the lowest corrosion current as much as 4.18×10~(-7)A. Moreover, it was able to increase the stability of the plating bath using membrane.

Galvanic Corrosion Resistance of Magnesium Alloy with Microarc Oxidation Film and Coating

Abstract: The magnesium alloy coupled with carbon steel experiences serious corrosion in atmosphere environment. Fortunately, it is simple and effective to increase the corrosion resistance of the Mg alloy by combining microarc oxidation (MAO) with coating. Thus the galvanic corrosion resistance of the Mg alloy treated by MAO and organic coating was studied making use of neutral salt spray test, humidity cabinet test, and simulated wet industrial atmosphere test. The corrosion resistance of various organic coating systems was compared as well. It was found that the combined system of MAO film/organic coating had good galvanic corrosion resistance for the Mg alloy. The increase in the corrosion resistance of the Mg alloy was closely related to the characteristics of the MAO film having good adsorption and interlocking effect with the organic coating. However, further work is needed to realize the satisfactory protection of the Mg alloy in severe corrosive environment by combining the MAO film and organic coating.

Mechanism of Tarnishing of Silver Plated Wares and Strategy to Prevent It

Abstract: The tarnishing corrosion mechanisms of silver plated wares in atmosphere were introduced. A comparison was made with respect to several methods to prevent silver plated coating from tarnishing and to their effectiveness and effect on the Ag coating performance as well. Moreover, the synthetic technology and properties of bi-phenol A polyaryl ester protective coating were briefed. It was pointed out that the sulfur ions in the atmosphere had the most significant effect on the corrosive tarnishing of the silver plated wares, while ultraviolet, oxidants, and corrosive mediums all contributed to accelerate the tarnishing of the silver plating.

Chromium-Containing Wastewater Treatment by Copperas Byproduct in Titanium Dioxide Production

Abstract: It is imperative to develop novel efficient technology for the treatment of Cr-containing wastewater, because various available methods for the treatment of Cr-containing wastewater have many limitations in practice. Thus copperas as the byproduct in the production of titanium dioxide (titanium white) was used as a reducing agent to treat Cr-containing wastewater. The process conditions were studied with respect to oxidation-reduction, neutralization-precipitation, separation, and so on. The optimum technological conditions were suggested as Fe/Cr ratio 20, pH value of oxidation-reduction reaction 3.5~4.0, oxidation-reduction time 15~20 min, pH value of neutralization reaction 6.5, and neutralization time 10~15 min. Moreover, the chromium in the wastewater containing about 35 mg/L was removed at a rate over 97.4%, and the Cr~(6+) content and total chromium were less than 0.50 mg/L and less than 1.0 mg/L, respectively, after treating using the optimized technological conditions. The treated water was qualified to the national discharge standard.

Effect of Working Voltage on Microstructure and Corrosion Resistance of Micro-Arc Oxidization Coating on MB5 Magnesium Alloy

Abstract: Micro-arc oxidation coatings of various compositions were prepared on the surface of MB5 magnesium alloy at different working voltages (102～200 V). The microstructure of the resulting micro-arc oxidization coatings was studied by means of scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). The corrosion resistance of the micro-arc oxide coatings was investigated using electrochemical test. The results showed that the working voltage had significant effects on the microstructure and composition of the oxide coating, which in turn directly affected the corrosion resistance of the magnesium alloy. During the micro-arc oxidation process, both the ions in solution and alloy elements in the magnesium alloy participated in the physico-chemical reaction in the micro-arc zone. The oxide coating was composed of α-MgF_2, MgO, Mg_2SiO_4 and MgAl_2O_4, while the content of MgO in the oxide coating greatly increased with increasing working voltage.

Electrochemical Properties of Copper Electrode Coated with Sn-In AlloyElectrochemical Plating in KOH Solution

Abstract: Sn,In,and Sn-In alloy coatings were deposited on the surface of current collector copper electrode via electrochemical routeThe hydrogen evolution electrochemical properties and electrochemical stabilities of the copper electrodes coated with electrochemical Sn,In,and Sn-In alloy in 1 mol/L KOH solution were studied,based on the measurement of the circular volt-ampere curves and electrochemical impedance spectroscopyIt was found that the copper electrodes coated with In and Sn-In alloy coatings had higher hydrogen evolution potentials than the uncoated copper electrode,ie,the hydrogen evolution potentials for the coated copper electrodes were larger than that of the uncoated one by 569 mV and 488 mV,respectivelyIn other words,the coated copper electrodes were capable of restricting hydrogen evolution more effectively than the uncoated electrodeIt was therefore anticipated that the cost-effective Sn-In alloy coated copper electrode of better ability to resist hydrogen evolution could find promising application in mercury-free battery industry,as the replacement of conventional In-coated copper electrode

Technology for Electroless Plating of Cu-Ni-P Alloy on Diamond

Abstract: Electroless Cu-Ni-P coating was prepared on the surface of diamond. The effects of bath composition, pH value, and plating time on the deposition rate were investigated, while the oxidation resistance of the diamond coated with the Cu-Ni-P electroless coating was analyzed using X-ray diffraction. As the results, it was feasible to prepare Cu-Ni-P alloy coating of good wear resistance, corrosion resistance, and conductivity on diamond using the optimal bath formula and plating conditions. The optimized plating bath was composed of 65~95 mg/L CuSO_4, 15~40 g/L NiSO_4, 15~30 g/L NaH_2PO_2, 5~20 g/L sodium citrate, 15~30 g/L NH_4Cl, and 12~35 mg/L KNO_3. The optimized bath pH value was suggested to be 4.5~7.6, while the temperature and plating time were suggested to be 75~95 ℃ and 15~35 min, respectively. The resulting Cu-Ni-P coating had good wear resistance and that after proper heat-treatment was able to further increase the oxidation resistance of the diamond.

Structure of Nickel-Tungsten Alloy Electroplating

Abstract: Nickeltungsten alloy coating was deposited on copper plate making use of electroplating in the bath composed of nickel sulfate, sodium tungstate, and trisodium citrate. The effects of the electrolyte concentration, current density, temperature, and pH on the composition and structure of the electroplated NiW alloy coating were investigated. The formation mechanism of the alloy coating was discussed based on Xray diffraction analysis. Results showed that the electroplated NiW alloy coating had a displacementpattern solid solution structure, with Ni as the solvent atom and W as the solute atom. Moreover, the size of the crystal grain of the NiW alloy coating significantly decreased with increasing W content in the coating, i.e., the crystal grain was gradually thinned with increasing W content in the coating.

Effect of Tin in Zinc Bath on Hot Dip Galvanized Coating of Silicon Containing Steel

Abstract: The hot dip galvanized coating on Si containing steel is usually gloom and over thick and has poor adhesion to the substrate. Thus tin was introduced into the zinc bath for the hot dip galvanization of 0.37%Si steel so as to modify the growth and microstructures of the galvanized coating. The thickness and microstructures of the resulting galvanized coatings prepared by immersing in the zinc bath containing various contents of Sn (with the mass fraction of Sn to be 0, 3%, 5%, 7%, and 12%, respectively) for different durations were determined and studied by means of electron probe microanalysis and scanning electron microscopy. The results showed that it was feasible to get rid of the over thickness of the coating by introduction of a proper amount of Sn into the zinc bath. As the Sn content in the zinc bath was less than or equaled to 5%, the coating thickness greatly decreased with increasing Sn content. When the Sn content was above 5%, the coating thickness assumed little change with further increase of the Sn content. Moreover, the addition of Sn to the zinc bath led to changes in the microstructure of the coating. Namely, at a Sn content over 5%, the δ layer became thick and compact, the ζ layer was much thin, and the microstructure of the ζ layer changed from loose massive crystal to regular columnar one. It was supposed that the coating thickness decrease in the presence of Sn was due to the formation of a Sn rich zone, which dominated over the formation of the ζ layer and acted to delay the Fe/Zn diffusion.

Chromium-Free Passivation Process for Zinc Coating

Abstract: A chromium-free colorful passivation technology for zinc coating was developed. Thus the beautiful rainbow-color-like passivation film was obtained on the zinc coating by properly controlling the passivation condition in the presence of major raw material molybdate and a synergistic inhibitor. The optimized passivation process was established, and the corrosion resistance of the molybdate conversion coating was investigated by means of electrochemical techniques using chromate conversion coating and zinc coating as the comparisons. It was found that the chromium-free passivation process based on the molybdate could be used to effectively increase the corrosion resistance of the zinc coating.

Chemical Milling Process for 2219 Aluminum Alloy Tube

Abstract: The chemical milling process for 2219 aluminum alloy tube was investigated using orthogonal test and the optimum formula and technology were established. It was found that the effect of various chemicals on the surface roughness of the chemically milled Al[LL] alloy was ranked as Na_2Sdissolved aluminumtriethanolamine (TEA)NaOH. The optimum composition of the chemical milling solution was suggested as 75~150 g/L NaOH, 6~15 g/L Na_2S, 38.5~42.0 g/L TEA, and 32.5~120.0 g/L dissolved aluminum. It was able to realize satisfactory chemical milling of the Al alloy using the optimized formulation. Namely, the chemically milled 2219 Al alloy tube had a surface roughness of 1.2~1.4 μm, a wall thickness tolerance below 0.12 mm, and a contour line deviation below 0.75 mm.

Effect of Metal Ion on Dip Zincing of Aluminum Alloy in Cyanide-Free Zinc Dipping Solution

Abstract: Cyanide-free solution for quaternary alloy zinc dipping of aluminum alloy was developed to substitute toxic cyanide complex solution for zinc dipping. The effect of metal ion on the stable potential in the dip plating process and the crystalline morphology and adhesive property of the replacement film were studied. The optimized composition of the solution for the zinc dipping was suggested as 75 g/L NaOH, 16 g/L ZnO, 0.8 g/L FeCl_3, 15 g/L NiSO_4, 0.6 g/L CuSO_4, 40 g/L EDTA, 15 g/L assistant complexing agent (organic polyacid complex), 15 g/L pyridine, and 1.2 g/L stablizer (polymer), and the temperature suggested as (20±2) ℃. The stable potential in the dip plating process assumed a positive shift with decreasing FeCl_3 content, which was beneficial to the refining of the crystalline, and the FeCl_3 content was suggested to be within 0.4~0.8 g/L. The amount of CuSO_4 had little effect on the stable potential in the dip plating process but the increase in the CuSO_4 content was beneficial to the refining of the replacement film crystalline, and the concentration of CuSO_4 was suggested to be 0.6~0.8 g/L. At a concentration of 15~30 g/L, NiSO_4 had little effect on the stable potential, while the potential assumed a stabilizing in 30 s and 20 s, respectively, for the first zinc dipping and the second zinc dipping. Moreover, the replacement film had good adhesion to the substrate.

Properties of Pulse Electrodeposited RE-Ni-W-B-PTFE-Al_2O_3 Composite Coating

Abstract: The components, surface morphologies, hardness, and wear resistance of pulse electrodeposited RE Ni W B PTFE Al_2O_3 composite coatings were studied The results showed that the introduction of pulse current and Al_2O_3 particulates contributed to increase the content of W and B in the RE Ni W B PTFE Al_2O_3 composite coatings The surface crack of the pulse electrodeposited RE Ni W B coating obviously decreased as compared with that of the DC electrodepositing The inclusion of Al_2O_3 antiwear particulates and PTFE friction-reducing particulates in the RE Ni W B coating was beneficial to eliminating the surface crack in the composite coating Besides, the larger the addition amount of Al_2O_3 particulates in the plating bath, the smaller the size of the crystalline grains in the RE Ni W B PTFE Al_2O3_ composite coating Moreover, the hardness of the RE Ni W B PTFE Al_2O_3 composite coating increased and the wear rate decreased with increasing Al_2O_3 concentration in the plating bath

Study of High Temperature Oxidation and Corrosion Resistance of Sol-Gel Alumina Coating on Titanium Alloy

Abstract: Alumina coating was prepared on the surface of titanium alloy using sol-gel method so as to improve the high-temperature oxidation resistance and service performance of the titanium alloy The oxidation-induced weight-gain of the alumina coating at 700 ℃ was measured, while the surface morphologies of the coating before and after the high-temperature oxidation were observed using a scanning electron microscope Moreover, the polarization curves of the coating and the Ti alloy substrate in aqueous solution of 35%NaCl were plottedIt was found that the weight-gain for the coating subject to heating at 700 ℃ for 20 h was 0028 0 mg/cm~2,much smaller than 1005 2 (mg/cm~2),that of the Ti alloy substrateAt the same time,the Δ E value for the coating was as much as 1 203 5 mV,much larger than 1546 mV,that of the Ti alloy substrate This indicated that the sol-gel Al_2O_3 coating on the Ti alloy surface had excellent corrosion resistance and could effectively increase the high temperature oxidation resistance and corrosion resistance of Ti alloy

Microbiologically Induced Corrosion of Materials

Abstract: A review is given to outline the research on the microbiologically induced corrosion of the ferrous metallic materials including iron, carbon steel, and stainless steel, nonferrous metallic materials such as aluminum, copper, nickel, titanium, and their alloys, and some nonmetallic industrial materials at home and abroad. The routes, mechanism, and controlling measures for the microbiologically induced corrosion of the materials were discussed.

Development of Polyester Acrylate Luminous Paint and Its Properties

Abstract: The methods to prepare polyester acrylate resin and SrAl_(2)O_(4):Eu~(2+) luminous materials were investigated with respect to the climate resistance,acid and alkali resistance,oil- proof ability,corrosion resistance,mechanical properties,and intensity and lasting time of persistent luminescence of the luminous paint made of the same.Thus the luminous paint of good coating performance was prepared by dispersing SrAl_(2)O_(4):Eu~(2+) in the colorless and transparent polyester acrylate resin.The resulting luminous paint had good light-penetrating ability,especially high ultraviolet penetration and small humidity penetration rate,excellent water-proof and climate-proof ability,excellent resistance to acid and alkali,good mechanical properties,and strong after-glowing luminance.After irradiation using a D65 light resource(200 lx) for 4 min,the luminous paint had 10 min and 60 min after-glowing luminance as much as 20 mcd/m~(2) and 6 mcd/m~(2),respectively,showing good persistent luminescence ability.The after-glowing duration for the luminous paint was over 1 000 min,indicating its potential as excellent luminous material.

Effects of Process Parameters on Thickness and Hardness of Micro-Arc Oxidation Aluminum Oxide Ceramic Coating

Abstract: The concept of oxidation power was introduced to reveal the action of energy during the micro-arc oxidation process. Thus micro-arc oxidation aluminum oxide coatings were prepared on LY12 Al alloy substrate at various process parameters using a pulse power supply. The thickness and hardness of the resulting ceramic coatings formed at fixed pulse width and frequency but varied duration and oxidation power were measured, and the changing tendencies of the thickness and hardness of the ceramic coatings with the process parameters were discussed. It was found that the hardness and thickness of the ceramic coatings tended to increase with increasing micro-arc oxidation power at fixed oxidation duration and area, while the thickness of the coating tended to increase with increasing micro-arc oxidation time and decrease with increasing workpiece area in case the other process parameters were kept constant.

Comparison of the Methods to Determine Rhodium Content in Plating Solution

Abstract: With a view to the importance to accurately determine the concentration of noble metal rhodium in plating solution, the applicability and precision of various methods including gravimetric method, inductively coupled plasma spectrometry (ICP), flame atomic absorption spectrometry (FAAS), and improved FAAS (IFAAS, where a calibration factor was used to optimize and calibrate the test method) for the measurement of rhodium were investigated and compared using a rhodium standard solution as the test object. As the results, it was suggested to measure the rhodium in the electroplating solution containing few impurities using the gravimetric method, which gave a deviation below 4%. Specifically, the deviation for the measurement of the rhodium using the gravimetric method was decreased to be less than 0.2% while sodium borohydride was used as the reducing agent. Moreover, the rhodium in the electroplating solution containing many impurities could be readily measured using ICP and IFAAS with good choice, and the relative deviation in this case was less than 1%.