Showing papers in "Materials protection in 2009"

Effect of Cerium Dioxide on the Structure and Wear-Resistance of Laser Cladding Ni-Based Cement Composite Coating

Abstract: A CO2 laser facility was performed to prepare Ni-based cement composite coatings with different content of CeO2 on the surface of AISI-1045 steel.The microhardness of the Ni-based ce-ment composite coatings was measured,and their microstructures and wear-resistance and corrosion-resistance were investigated.In particular,the effect of rare-earth oxide Ce02on the wear-resist-ance and corrosion-resistance and antioxidation ability of the com-posite coating was highlighted.Results showed that the introduction of a small amount of CeO2(0.6%)led to considerable de-crease of cracks,holes and entrapped impurities in the cement composite coatings.It also contributed to decrease the grain size,promote the uniformity of the microstructure,increase the microhardneas,and significantly improve the wear-resistance and corro-sion-resistance of the cement composite coatings.

Comparative Analysis of Salt Spray Test Standards ISO 9227:2006 and ISO 9227:1990

Abstract: A comparison was made between salt spray lest stand-ards ISO 9227:2006 and ISO 9227:1990 in relation to introduc-tion and scope, test solution, apparatus, method to evaluate the corrosivity of the salt-spray chamber, specimen and arrangement, evaluation of results and test report Hopefully, the comparison and analysis conducted would help to provide reference for those who use or establish the standards It is suggested that modifica-tion be made to GB/T 10125 -1997 standard in due course

Corrosion Inhibition Performance of Phosphonic Chitosan for Carbon Steel in Seawater

Abstract: Water-soluble phosphonic chitosan was synthesized atacidic condition. The inhibitive properties of the resulting phos-phonic chitosan for mild steel in seawater were studied usingweight loss test and electrochemical test. Results show that thehighest inhibitive efficiency of phosphonic chitosan, which is asmuch as 73.05%, is obtained at a dosage of 400 mg/L, and thehigh inhibition efficiency can be retained for a long time.Moreover, the synthesized phosphonic chitosan as an inhibitor isable to inhibit the corrosion of carbon steel in seawater at bothambient and elevated temperatures, showing promising potentialas a high-efficiency inhibitor in seawater.

Mechanisms for the Formation of Porous Micro-Arc Oxidation Coatings on Magnesium Alloys

Abstract: Micro-arc oxidation ceramic(MAO)coating was prepared on AZ91 magnesium alloy from a silicate alkaline solution composed of 5.0～ 30.0g/L Na2 SiO3,1.0-5.0 g/L NaOH,5.0-8.0 g/L KF,0.5～2.0 g/L Na3C6H5Q7,and 0.5～2.0 g/L ethylene diamine tetraacetic acid(EDTA),in alternating current galvanostatic mode and at a cur-rent density of 20-50 A/dm2.The surface and cross-section morphologies of the MAO coating were observed using a transmis-sion electron microscope(TEM)and scanning electron micro-scope(SEM),and the mechanisms for the formation of porous microstructures of the MAO coating were discussed.Results indi-cated that two types of pores,i.e.,honeycomb-like and bean-shaped pores were formed in the MAO coating.The formation and growth processes of the MAO coating included initiating,grow-ing,connecting,merging,and nesting processes of the pores.The formation of the porous coating on the surface of Mg alloys was dominated by layer-by-layer growth,while the pore initiation was dominated by gas ejecting mechanism and the pore develop-ment by cellular evolution mechanism.

Factors Affecting the Corrosion Behavior of Tubular Steel N80 in CO_2-and H_2S-Containing Produced Water of Gas Well

Abstract: Weight loss method was used to investigate the effects of various factors on the corrosion behavior of tubular steel N80 in produced water of a natural gas well in Changqing area. Results show that under the experimental conditions,the corrosion rate first increased and then decreased with the increase of temperature, and the maximum corrosion rate was recorded at 60 ℃. The effect of Cl-was similar to that of temperature, and the maximum corrosion rate was recorded at a Cl-concentration of 30 g/L. Besides, the corrosion rate constantly decreased with increasing pH value and reached a minimum value at a pH value of 8.0. Moreover, the corrosion rate of the tubular steel monotonously increased with increasing partial pressure of CO2,but it initially decreased and then slowly increased with increasing partial pressure of H2S.

Performance of Oxalate Chemical Conversion Coating on Magnesium Alloy

Abstract: Oxalate conversion coating was prepared on the surface of magnesium alloy so as to improve the adhesion and protective performance of 3C products and provide long-term stable ma-chined surfaces.The performance of the oxalate chemical conver-sion coating on magnesium alloy for 3C products was investigated in relation to relevant surface analysis techniques and standard as well.Results show that the oxalate coating appears to be milky and is mainly composed of fine and compact particles.Moreover,the oxalate coating retained its color after being wiped with alco-hol-cotton for over 50 times and had an electric resistance of be-low 0.1 Ω and salt spray endurance of over 24 h,meeting with the requirements specified by relevant IBM standard.

Microwave Absorbance Behavior of Expanded Graphite-Based Composite Electroless Plated with Metallic and Alloy Coatings

Abstract: Expanded graphite was electroless plated with Ni, Ni-Co alloy, and Ni-Fe-Co alloy. The electroless plated expanded graphite was then mixed into paraffin forming a composite for micro-wave absorbance. The morphology and composition of the eleelroiess coatings were analyzed bv means of scanning electron microscopy andenergy dispersive spectrometry.The complex relative permittivity(e = e'-je")and permeability (μ=μ'-jμ") of the expanded graphite- based composite absorber were measured in a frequency range of 2 ~ 18 GHz. The reflection loss (R. L), matching thickness (dm) and matching frequency (fm) of the composite absorber were calculated based on the theory of absorbing wall. Results indicate that the thicknees of the electroless metallic and alloy coatings on the surface of expanded graphite is 70～150 nm. At a matching thick-ness of 0. 3 mm, the composite absorber has a maximum reflectioncoefficient of about-28 dB, the corresponding match frequency is 13.5 GHz. Moreover, the frequency width below an R. L of-10 dB is 7.5 GHz. In general, the composite absorber is qualified in terms of the cbaracteristics including light weight, small thickness, wide frequency range, and strong absorbance capacity.

Inhibition Behavior and Mechanism of Tungstate Compound Inhibitor for Carbon Steel in Seawater

Abstract: The corrosion inhibition performance and mechanism of atungstate-based composite inhibitor for carbon steel in seawater were investigated by using weight loss test, polarization curve meas-urement , and analysis of scanning electron microscopy and energy dispersive spectrometry. Results indicate that the inhibition effi-ciency increase with increasing concentration of single tungstate, but single tungstate inhibitor has low inhibition efficiency. Contraryto the above, an inhibitor formulated from tungstate, sodium cit-rate, 1-hydroxy -1,1 -ethyledine disodium phosphonate ( HEDP) and Zn2+ had syncrgistic inhibition effect. The one composed of 30 mg/L tungstate, 40 mg/L sodium citrate, 10 mg/L HEDP, and 3 mg/L Zn2+ had an inhibition efficiency of over 93%. Both the sin-gle tungstate and tungstate-based composite inhibitors are anodic corrosion inhibitors. A compact film containing iron oxide as themajor ingredient and a small amount of W and P was formed on the surface of carbon steel exposed to seawater in the presence of the inhibitors. The insoluble precipitation film is able to effectively in-hibit the corrosion of carbon steel in seawater.

Technology for Cyanogen-Free Electroplating of Magnesium Alloy Castings

Abstract: Environmentally acceptable technology forcyanogen-free electroplating of magnesium alloy castings was in-vestigated with respect to pretreatment procedures including alka-line washing, acid pickling, activation, and the first and second zinc immersion. It was found that the alkaline electroplated Zn coating prepared after zinc immersion was compact and had good corrosion resistance. Moreover, the Mg alloy substrate after zinc immersion treatment was applicable to Cu electroplating from an organic phosphoric acid bath, and the resulting Cu coating had satisfactory appearance and adhesion to substrate and small poros-ity as well.

Properties of Galvanized Steel Passivated by Silane and Rare Earth Cerium and Lanthanum

Abstract: Amino-propyl-triethoxyl silane (γ-APS) was coopera-ted with rare earth salts of cerium and lanthanum to passivate gal-vanized steel. Thus self-assembled monolayer of-y-APS was first-ly prepared on the galvanized steel,followed by introducing of rare earth conversion coatings to generate silane -rare earth com-posite passivation coatings. The corrosion protection ability of the composite passivation coating was studied via electrochemical im-pedance spectroscopy and neutral salt spray test. The morphology of the composite coating was observed using an atomic force mi-croscope. And the film-formation mechanism and corrosion resist-ant mechanism of the composite passivation coating were ex-plored. Results indicate that the compactness and corrosion re-sistance of the composite coating was significantly improved as compared with self-assembled silane film or rare earth conversion coating. And silane -cerium salt composite coating had a salt -spray lifespan of 76h,showing better corrosion resistance than si-lane -lanthanum salt composite coating. Moreover,the composite coating was smoother than self-assembled silane film or rare earth conversion coating. Owing to the synergistic effect between silane and rare earth,the deposition of the rare earth conversion film on galvanized steel was promoted.

Influence of Alloying Elements Cu and Cr on the Corrosion Resistance of Weathering Steels in Simulated Ocean Atmospheric Environment

Abstract: The corrosion behaviors of Q235 and five kinds of weathering steels containing different contents of alloying elements Cu and Cr in simulated ocean atmos-pheric environment were studied using wet-dry cyclic corrosion tests in the solution of 0.5% NaCl.The compositions of the rus-ted layers on the steels were analyzed by means of X-ray diffrac-tion.Results indicated that in Cl-containing environment,the introduction of Cr alone(0-3%)or Cu alone(0.25% ~ 0.50%)led to no significant improvement on the corrosion resist-ance of the steels.Increasing the content of Cr in the steels con-tributed to restrain the corrosion of the steels in the early stage of corrosion but led to damage to the corrosion resistance in a long-run.Contrary to the above,increasing the content of Cu helped to retard the corrosion of the steel at extended corrosion duration.Moreover,it was feasible to significantly improve the corrosion re-sistance of the weathering steels simultaneously increasing the contents of alloying elements Cu and Cr,but the alloying ele-ments had little effects on the compositions of the top rusted lay-ers.And the corrosion products were composed of γ-FeOOH,Fe3O4,γ-Fe2O3,and a small amount of α-FeOOH.

Protection of Aluminum Alloys by Silicate-Based Organic-Inorganic Hybrid Coatings

Abstract: A sol was prepared using tetraethyl orthosilicate(TEOS)as the raw material.The resulting sol was painted onto the surface of Al al-loys and properly heat-treated to generate organic-inorganic hy-brid coatings,aiming at improving the corrosion resistance of the Al alloys.The microstructure and properties of the coatingB were analyzed using an electrochemical device and a scanning electron microscope.Results indicated that the coatings combine the ad-vantages of both organic and inorganic species,making it feasible to well protect the Al alloys substrata.The coated specimen had a corrosion current of(4.26～6.58)×10-6 A/cm2,showing pro-tection comparable to conventional Cr(VI)electroplated coating for Al alloys.Moreover,the present coating was capable of effec-tively preventing Al alloys from corrosion in Cl-containing neutral aqueous solutions,and no harmful chemicals were discharged a-long with the present technology,showing environmental accepta-bility.

Technology for Solid-State Pack Boronizing of Q235 Steel and Kinetic Study of Boron Diffusion in Steel

Abstract: Q235 steel was pack boronized with solid-state agent. An attempt was made to investigate the possibility of predicting the thickness variation of boride layers. The experimental data were fitted with Sigma Plot 10. 0 software. The iso-thickness diagram of the bondinglayer was obtained, making it feasible to predict the thickness of the boriding layer by giving bonding temperature and time,and to determine suitable boriding temperature and time according to the target thickness of the boriding layer. Moreover, the diffusion fac-tors such as diffusion activation energy and diffusion rate constant of the Q235 steel were analyzed with kinetics method according to the thickness of the boronized layers under different temperatures. Results indicate that boriding layer formed on the Q235 steel sur-face has saw-tooth morphology and is composed of single phase Fe, B. The diffusion rate constant (K) of boron atoms in the 0235 steel at 800 ℃, 850℃,and 900 °C were calculated to be 1.074×10-13, 1.622×10-13m2/s, and 3.921×10-13m2/s, respectively, and the average diffusion activation energy ( Q) of boron atoms therein was determined to be 134.473 kJ/mol.

Progress in Research on Corrosion Characteristics and Corrosion Resistance of Magnesium Alloys

Abstract: A review is provided of the progress in the research of corrosion characteristics and cor-rosion resistance of magnesium and its alloysIt is pointed out that the poor corrosion resistance of Mg is attributed to its high chemical activity and low equilibrium potential,which has been preventing the wide application of magnesium and its alloys

Influence of Nano SiC on Phase Composition and Properties of Inside Ceramic Lining Coating Prepared on Composite Pipes by Gravitational Separation Self-Propagation High-Temperature Synthesis

Abstract: Ceramic lining coating was prepared on the inside sur-faces of composite pipes by gravitational separation self-propaga-ting high - temperature synthesis ( SHS) with (Al-Fe2 O3 - CuO) plus SiO2 as the aluminothermic reactants, aiming at increasing the compactness and hardness of the lining and broaden its appli-cation scope. The effect of nano SiC additive on the phase compo-sition of the ceramic coating was investigated by means of X - ray diffraction. It was found that the ceramic coating was mainly com-posed of a - A12O3 and contained a small amount of hercynite FeAl2O4, sillimanite Al2SiO5, and SiC. SiC added in the react-ant system retained its phase structure after high-temperature syn-thesis, and it was able to effectively prevent matrix grains from growth and abnormal growing up, hence increasing the hardness and compactness of the ceramic lining coating.

Progress of Electrodeposition Technology for Preparing Nano-Multilayers

Abstract: A review is given about the progress of the electrodeposition technolo-gy for preparing nano-multilayers. The problems commonly emer-ging along with electrodeposition are summarized, and the essential causes leading to the problems are analyzed. Moreover, several principles have been suggested in relation to the selection of electro-lytes so as to solve those problems.

Composition of Rusted Layers in Atmosphere and Anticorrosion Mechanisms of Weathering Steels

Abstract: Accelerated dry-wet cyclic immersion tests were carried out at lab to simulate the immersed corrosion test of steels in industrial atmosphere,where the weight-losses of weath-ering steels and carbon steels were measuredThus the composi-tions and electrochemical properties of the rusted layers on the weathering steels and carbon steels exposed to atmosphere were investigated,and the corrosion mechanism of the rusted layers were discussed based on analyses of scanning electron microsco-py,X-ray diffraction,and anode polarization testingResults in-dicated that the rusted layers formed on the weathering steels dur-ing the initial corrosion period were mainly composed of a-FeOOH,and that on the carbon steels were mainly composed of Fe2O3Moreover,the size of α-FeOOH crystal was very small,and the rusted layers were compact and had protective functionHowever,the size of Fe2 O3 crystal was very big,and the rusted layers were loose and porous,showing no protective functionIn one word,the rusted layers on the weathering steels exposed to industrial atmosphere had passivation function and could protect the steels from corrosion

The Corrosion Inhibition Performance of Imidazoline Inhibitor for Carbon Steel in Hydrogen Chloride Solution

Abstract: Corrosion inhibitor imidazoline was prepared by using dodecanoic acid and diethylenetriamine as the raw materials.The corrosion inhibition performance of imidazoline for carbon steel A3 in 5 % HC1 solution was evaluated by measurement of static weight-loss and linear scanning polarization curve, and its synergistic inhibition action with KI was investigated.Results indicate that the imidazoline as an inhibitor is effective to retard the corrosion of the carbon steel, and a corrosion inhibition rate of 99% is recorded at an inhibitor concentration of 30 mg/L.This is because the imidazoline inhibitor is able to effectively inhibit the anode reaction.Moreover, the imidazoline inhibitor had good synergistic effect with KI.Namely, a corrosion inhibition rate of as much as 99.2% was reached when 10 mg/L inhibitor was mixed with 10 mg/L KI, and the corrosion rate was well controlled below 0.6 g/( m2· h).

Antiwear and Anticorrosion Behaviors of Magnetron Sputtered (Ti_xAl_y) N Film on 6063 Aluminum AUoy

Abstract: (TixAly)N film was prepared on the surface of 6063 Al alloy by magnetron sputtering,aiming at broadening its application scope and in-creasing its service life.The thickness and hardness of the film were measured using a thickness meter and microhardness tester,respectively,while its phase composition and morphology were analyzed by means of X-ray diffraction and scanning electron mi-croscopy.It was found that the(Tix Aly)N film contributed to greatly increase the hardness of 6063 Al alloy substrate,which was attributed to the strengthening effect of hard phases such as TiN,A1N,and Ti3AlN.At the same time,(TixAly)N film pre-pared by magnetron sputtering was superior to conventional anodic oxidation coatings on Al alloy in terms of the compactness,adhe-sion to substrate,and effectiveness in increasing the antiwear and anticorrosion behaviors of the Al alloy substrate.This could make it feasible for the magnetron sputtered(Tix Aly)N film to find promising applications in decoration industry.

Electrochemical Corrosion Behavior of Weld Joint of Hot Rolled Austenite Stainless Steel Plates

Abstract: Low carbon stainless steel ER308L was used for tungsten inert gas ( TIG) arc welding of 304 stainless steel ( SUS304).The electrochemical corrosion behavior and electrochemical eigen-values in different solutions of the welded metal of hot rolled SUS304 austenite stainless steel plates weretested, and the susceptibility of the welded joint to intergranul arattack was examined.Results show that the resistance of the welded metal to electrochemical corrosion initially decreased andthen increased with increasing concentration of H2SO4 concentration.The poorest corrosion resistance was recorded at a H2SO4 concentration of 60%.At the same time, the resistance of the welded metal to electrochemical corrosion was continuously decreased with increasing concentration of HCl, while a very shortpassivation zone and a long activation zone were separately observed.Besides, a very long passivation zone was recorded in mix-acid, but no remarkable passivation flatform was detected there in.Moreover, remarkable pitting corrosion was recorded on theanode polarization curve in 6% FeCl3.In general, the weld metal had better resistance to electrochemical corrosion than that of the base metal, and the electrochemical corrosion data of the welded metal in HC1 and H2SO4.solutions agreed well with that of immersion corrosion tests.And no intergranular attack was observed forthe welded joint.