Showing papers in "Materials protection in 2007"

Analysis and Evaluation of Causes Leading to Corrosion of Coal Tar Rectification Tower

Abstract: A survey was made about the use and corrosion of coal tar rectification tower in engineering.Thus the causes leading to corrosion of the rectification tower were analyzed,based on investigation of the microstructures of the materials for construction of the tower,the corrosive medium,and the corrosion products by means of metallographic microscopy,energy dispersion spectroscopy,inductively coupled plasma spectrophotometry,and X-ray diffraction.The uniform corrosion rate was measured by measuring the thickness change of the tower board in a certain period.Results indicated that the inner wall of the tower was made of 316L austenitic stainless steel containing a small amount of ferrite.Because a lot of sulfur ions and chlorine ions existed in the corrosive medium,the stainless steel was liable to pitting corrosion.At the same time,there was a large amount of S in the corrosion products,appearing as Fe7S8.The tower board with a thickness of 4 mm experienced overall corrosion in 2 years,but its corrosion destruction duration was much less than 2 years,owing to the pitting corrosion.Therefore,the 316L stainless steel was not suitable to be used as the structural material of the coal tar rectification material.

Determination of Phosphorous Content in Electroless Ni-P Coating by Quinoline Phosphomolybdate Gravimetric Method

Abstract: The application of quinoline phosphomolybdate gravimetric method in the determination of phosphorus content in electroless Ni-P coating was introduced.The relevant measurement results were compared with that determined by national standard spectrophotometric method GB/T 13913-92 and energy dispersive spectroscopic(EDS) method as well.It was found that the relative error for the determination of P in electroless Ni-P coating using the titled method was within-1.65%~4.21%,indicating that the method could be well used to determine the phosphorus content in the electroless Ni-P coating.Moreover,the corresponding EDS measurement result for the same electroless Ni-P coating was relatively larger as compared with the result determined using the titled method.

Analysis of Loss in Current Efficiency of Aluminum Alloy Sacrificial Anode in Aqueous Sodium Chloride

Abstract: The current efficiency and hydrogen-evolution rate of aluminum sacrificial anodes made of Al-based alloys Al-Zn-In-Sn-Mg-RE and Al-Zn-In-Sn-Si corroded in 3%NaCl aqueous solution at 60 ℃ were analyzed using constant current method.The morphologies,microstructures,and compositions of the precipitated phase of the corroded Al-alloy sacrificial anodes were analyzed by means of scanning electron microscopy and energy dispersive spectroscopy.The results showed that the decrease in the current efficiency was attributed to both the hydrogen evolution self-corrosion and mechanical detachment as well.The alloying elements were separated out as coarse second phase at the grain boundary,which together with the cathodic impurities Fe and Si led to the hydrogen evolution and mechanical loss of the Al-alloy sacrificial anodes.However,the mechanical loss of the Al-alloy sacrificial anodes was mainly attributed to the segregation phases of the alloying elements but not the cathodic impurities Fe or Si.

Research of Zinc Species Phosphating Solution Modified with Barium Salt at Ambient Temperature

Abstract: The zinc species phosphating process at ambient temperature and the morphologies and properties of the phosphating coatings were analyzed by means of scanning electron microscopy,energy dispersive spectroscopy,and corrosion test in NaCl solution,which was aiming at revealing the effects of barium nitrate and SO2-4 on the anticorrosion behavior of the phosphating coating and the phosphating process as well.It was found that SO2-4 in the phosphating bath was incorporated into the phosphating coating and was unable to be removed by rinsing,which was harmful to the properties of the phosphating coating and could even lead to failure of the phosphating bath.Fortunately,the SO2-4 in the phosphating bath could be effectively removed by the introduction of Ba2+ at a concentration of ≤0.9 g/L,which helped to modify the composition and increase the anticorrosion behavior of the phosphating coating.

Study of Oxidation Prevention of H13 Steel at Elevated Temperature by Glass-Based Antioxidation Paint

Abstract: A glass-based high-temperature antioxidation paint was developed to reduce the loss of metal materials by high-temperature oxidation during heat treatment process.The effectiveness of the glass-based high-temperature antioxidation paint in preventing the oxidization of H13 steel was investigated using high-temperature oxidation testing.At the same time,the action mechanisms of the paint in preventing the H13 steel from oxidation at elevated temperature were explored as well.Results indicated that the glass-based paint mainly composed of SiO2 and B2O3 was capable of effectively preventing the H13 steel from oxidation within a temperature range of 800-1100 ℃.It was anticipated that the glass-based high-temperature antioxidation paint would find promising application in engineering.

Corrosion and Protection of Sintered Nd-Fe-B Magnets

Abstract: Corrosion behaviors of sintered Nd-Fe-B magnets in various corrosion environments were investigated In order to improve the corrosion resistanance of sintered Nd-Fe-B magnets, two methods were introduced One was surface coating and the other was additin of alloying elements Some sophisticated technologies and research hotspots of surface coating were evaluated, then some questions on corrosion protect of sintered Nd-Fe-B magnets which could be paid attention to in followed research were presented

The Process for and Application of Electroless Ni-W-P Coating

Abstract: Orthogonal test was employed to prepare electroless Ni-W-P coating with better corrosion-resistance than electroless Ni-P alloy coatingThus the optimized parameters for the preparation of the electroless Ni-W-P coating were establishedThe effects of the concentrations of various bath ingredients and additives on the deposition rate and corrosion rate of the Ni-W-P coating in 5% sulfuric acid solution at 60 ℃ were investigatedThe corrosion resistance of the coating was examined based on measurement of Tafel curves via electrochemical routeBesides,the elemental composition of the coating was determined by means of energy dispersive spectroscopyIt was found that the Ni-W-P coating had much better corrosion resistance than amorphous Ni-P coatingThe content of P and W in the coating was 1400%and 369%(mass fraction),respectivelyThe corresponding optimized process for the preparation of electroless Ni-W-P coating had been successfully used for the corrosion protection of an air-cooler

Development of Deposition Mechanism and Corrosion Mechanism of Zinc-Nickel Alloy Coatings

Abstract: The high corrosion resistance, good formability and weldability of zinc-nickel alloy coatings has attracted much attention. The research development of deposition mechanism and corrosion mechanism of zinc-nickel alloy coatings was summarized in this paper.

Effect of Cu, Mn on the Corrosion Performance of Carbon Steels in Wet/Dry Environments

Abstract: The atmospheric corrosion performance of Mn - and Cu - bearing steels was studied by dry/wet cycb'c corrosion tests (CCT) with 60% relative humidity at 30 ℃. The salt droplet used for CCT was 0. 3% NaCl solution. The rusted specimens were investigated by gravimetry, electrochemical techniques and XRD analysis. The results showed that the steel containing 0. 30%Cu showed higher corrosion resistance than plain carbon steel due to the accelerated rust reduction in cathodic region, which facilitated the formation of the inner rust layer containing more Fe3O4. While the 1. 43 % Mn - bearing steel showed a worse corrosion resistance than carbon steel owing to the depressed cathodic reduction and accelerated dissolution of iron in anode.

Pitting Corrosion Behavior of BFe30-1-1 Alloy in NaCl Solution

Abstract: The pitting corrosion behavior of BFe30-1-1 alloy in NaCl solutions was investigated.Thus the anodic polarization curves and pitting potentials of the BFe30-1-1 alloy in NaCl solutions of various pH values were measured.The concentrations of Cu2+ and Ni2+ in the solutions were measured using atomic absorption photospectroscopy.The morphology of the pitting corroded alloy surface and the elemental composition of the corroded cross-section were analyzed by means of scanning electron microscopy.Moreover,the corrosion products were analyzed by means of X-ray diffraction.It was found that the BFe30-1-1 alloy showed similar corrosion behavior in acidity NaCl solution and mild alkaline NaCl solution.It had better corrosion resistance at low potential in strong alkaline solution than in acidity and mild alkaline solutions,which was because a stable passive film was formed on the surface of the alloy immersed in 0.5 mol/L NaCl solution with a pH value of 14.Moreover,corrosion characterized by nickel peeling off occurred in the pitting corrosion of the BFe30-1-1 alloy.

Research on Galvanic Corrosion Behavior of the U71Mn Rail Steel and Stainless Steel in the Simulated Rain Environment

Abstract: Galvanic corrosion behaviors of rail steel U71 Mn and stainless steel including 1Crl3,2Crl3 and 1Cr18Ni9 were investigated by electrochemical test and salt spray test in the simulated rain environment in order to solve the inspection problem of train location in railway station. The results indicated that the galvanic corrosion sensitivity of the U71Mn steel with three stainless steels was high. The galvanic corrosion sensitivity of the U71 Mn steel with the three stainless steels was similar in the simulated sour rain environment, while the galvanic corrosion current of the U71 Mn steel coupled with 1Cr18Ni9 was the highest one among the three galvanic couples in simulated neutral environment. For the welded structure of large U71 Mn steel cathode coupled with small stainless steel anode in simulated sour rain environment, the stainless steel cathode was eroded slightly and U71 Mn anode was eroded remarkably, but the self-corrosion of the rail steel was primary and galvanic corrosion was secondary. The rail steel U71Mn welded by lCrl3 steel in neutral rain environment or by lCrl8Ni9 steel in acid rain environment could be used to solve the problem of inspecting train location in railway station.

Progress in Study of Duplex Surface Treatment of Chromium Electroplating and High Energy Beam

Abstract: A review was given on the principles,purposes and practical effectiveness of chromium electroplating/ laser surface strengthening,plasma nitriding/chromium electroplating,and substrate laser pre-quenching/ chromium electroplating as the duplex surface treatment techniques.The mechanisms for the substrate laser pre-quenching plus chromium electroplating as a duplex surface treatment process to increase the service life of the chromium-plated gun tubes were discussed based on experimental exploration.It was pointed out that,according to the different interfacial strengthening mechanisms of high energy beam irradiation and chromium electroplating,the duplex surface treatment technique of chromium electroplating and high energy beam irradiation can be divided into two categories: high energy beam hardening of electroplated chromium coatings and the hybrid process of substrate high-energy-beam pre-treating plus chromium post-electroplating.The typical examples of the former include laser surface hardening(plasma nitriding) of electrodeposited chromium coatings,while the representative of the latter is the duplex treatment of substrate laser pre-quenching plus chromium post-electroplating.

Influence of Temperature on Initial Corrosion of LY12 in Marine Atmosphere

Abstract: A series of accelerated corrosion tests was conducted in simulated marine atmosphere to study the initial corrosion behavior of LY12 aluminum alloy under different temperaturesThe variations in the corroded morphology,weight gain,maximum pitting depth and electrochemical parameters(corrosion potential,AC impedance)with temperature were investigatedResults showed that the LY12 aluminum alloy with about 1 mg/100 cm2 Cl-experienced pitting in a few days within a temperature range of 5～75 ℃,and there did not exist a critical temperature point at which non-corrosion transformed to corrosionIn general,the weight gain and maximum pitting depth increased with rising temperature,and the variation in the weight gain with time at different temperatures well fitted model BoltzmanMoreover,for the pitting corroded surface of LY12 at different temperatures in simulated marine atmosphere,the open circuit electric potential kept almost unchanged,and Nyquist graph was recorded in terms of the adsorbent resisting system

Preparation of Phosphorus-Free Water-Based Cleaning Agent for Metals

Abstract: The compound systems of anionic-cationic surfactants were used to prepare water-based cleaning agents for metals.Thus the auxiliary cleaning capacity of the sodium salt of maleic anhydride-acrylic acid copolymer and sodium tripolyphosphate-4A zeolite was compared.The anionic-cationic surfactants were then used as the auxiliary cleaning agents and introduced into the sodium salt of maleic anhydride-acrylic acid copolymer(coded as Na-CP4) and sodium silicate at a mass ratio of 95:5 to prepare the titled complex cleaning agents for metals.The optimized formulation of the complex metal cleaning agents was experimentally established,while the cleaning performance and antirust behavior of the dilute solution(5%) of the complex metal cleaning agent were evaluated as well.As the results,the optimized formulation for the target P-free water-based metal cleaning agent was suggested to be NESA(C12 fatty alcohol polyoxyethyl ether-ammonium sulfate):BJH1(fatty amine,prepared at our lab):OP-10(octyl-phenol polyoxyethyl ether):M550(copolymer of halogenated dimethyl dipropyl amine acrylic acylamine) = 6:4:4:1(molar ratio).The final cleaning agent had good decontamination capacity and antirust ability as well,and was environmentally acceptable owing to the absence of phosphorus.

Preparation and Characterization of Composite Silylanized Finn Layer on Al Alloy Surface

Abstract: In order to improve corrosion resistance of Al alloys surface and the bonding durability between Al alloy substance and organic coating, Al alloy was cooked firstly in de-ionized water at 65 ℃ for 15 min and oxyhydroxide layer on Al alloy surface was formed, and then bis - [ triethoxysilyl-propyl] tetrasulfide ( BTSPS) and γglycidoxypropyltrimentox-ysilane (GPTMS) composite silylanization film layer was fashioned on oxidized Al alloy surface by a two- step dip- coating process with further cure at 100 ℃ for 60 min. The composite film layers were analyzed and characterized with reflection - absorption FTIR spectrum, atomic emission spectroscopy ( AES) and scanning electron microscopy ( SEM). The results showed that Al - O - Si covalent bond network were formed between oxyhydroxide film layer on Al alloy and BTSPS inner film layer, Si - 0 - Si covalent bond network are done between inner BTSPS and GPTMS outer layer. Epoxy ethyl group lies outmost the composite film layer.

Study of Corrosion Resistance of Chemical ConversionGoatings on Magnesium Alloy Substrate

Abstract: Chemical conversion coating was prepared on magnesium alloy substrate using aqueous solution of KMnO4 plus Na3PO4 containing NaNO3 inhibitor as the conversion liquid. At the same time, phytic acid was used as an environmentally friendly conversion agent to prepare conversion coating on the Mg alloy substrate as well. The morphologies and elemental compositions of the two types of chemical conversion coatings were analyzed by means of scanning electron microscopy and energy dispersive spectroscopy. The effects of pH value, temperature, conversion duration, and mass fraction of phytic acid on the morphology and corrosion resistance of the conversion coating were investigated, while the corrosion resistance of the types of chemical conversion coatings on Mg alloy substrate was compared. It was found that the two types of chemical conversion coatings on Mg alloy substrate were more smooth and compact than the chromale convention coating and had corrosion resistance comparable to that of the chromate convention coating. Moreover, the phytic arid conversion coaling mainly composed of phytate showed self-healing ability after being corroded in 3.5% NaCI solution.

Effect of Ce~(4+) Ions on Formation Process of Alumina Anodized Coating

Abstract: The effect of Ce4+ ions on the formation process of anodized porous alumina film in 03 mol/L sulfuric acid electrolyte was investigatedThe resulting as-prepared porous alumina film was characterized by means of scanning electron microscopy and X-ray diffractionResults showed that the addition of Ce4+ led to changes in the current density during the film formation process but had no effect on the film formation process itselfMoreover,Ce4+ ions were not incorporated into the oxide film,though they helped to make the pores in the oxide film more better ordered

Prevention of Tubular Copper Conductor in Water-Cooling Generator

Abstract: On the basis of expounding the corrosion mechanism of the tubular copper conductor in the water-cooling generator, four methods of preventing corrosion of the tubular copper conductor in the water- cooling generator have been proposed. The corrosion of the tubular copper conductor could be prevented effectively and conveniently by keeping pH of the cooling water between 7. 5 and 8.0 by adding amine to the deionized water or giving partly the condensed water to the cooling water, and by adding low dosage and high efficiency copper inhibitor to the cooling water. The result of inhibitor application on the spot showed that the added dosage of the inhibitor developed by us was low, being lower than 5 mg/L, and that the efficiency of the inhibitor to copper was good, and the quality of the cooling water was stable. During the period that the inhibitor was added to the cooling water, the conductivity of the cooling water was lower than 2. 0 μS/cm, the content of copper in the cooling water is lower than 40 μg/L.the pH in the cooling water was higher than 6. 8.

Effect of Composite Ceramic Coatings on the Corrosion Resistance of Carbon Steel——Electrochemical Study

Abstract: The effect of composite ceramic coatings(Al2O3,SiC,ZrO2) on the corrosion resistance of carbon steel was investigated using electrochemical impedance spectroscopy(EIS).The correlation among the impedance characteristics and the structure and properties of the composite ceramic coatings was explored.It was found that the ZrO2 composite ceramic coating showed better corrosion resistance than the other two kinds of composite ceramic coatings.

Application of Self-Propagating High Temperature Synthesis Combined with Powder Metallurgy and Foundry in Preparation of Cermet Composite

Abstract: The applicability of self-propagating high temperature synthesis(SHS)combined with powder metallurgy and foundry in the preparation of cermet composites was investigated.Thus the pre-selected and well mixed raw materials powders were pressed into blocks and adhered onto the mould or directly adhered onto the mould.The SHS reaction was initiated via casting of melted metallic fluid,during which the metallic fluid was permeated into the micropores and forged into a whole body with the metallic matrix.The resulting in-situ synthetic cermet composite had a surface layer to be as thick as 3-20 mm and would have promising application in engineering.

Corrosion Inhibition of 16 Mn Steel by Phytic Acid Salt

Abstract: The corrosion inhibiting action of phytic acid salt to 16 Mn steel was investigated using weight loss method and polarization curve method. It was found that phytic acid salt had good corrosion inhibiting effect for 16 Mn steel in the mixed medium of crude oil and 3.5% sodium chloride at 50 ℃. More important, the phytic acid salt combined with sodium dodecyl -benzene - sulfonate (SDBS) and polyglycol octyl - phenyl ether ( POPE) showed considerably improved corrosion inhibition capability for the Mn steel, owing to a synergistic corrosion inhibition function among the three ingredients. The optimized formulation of the composite corrosion - inhibition agent was suggested to be 100 mg/L phytic acid salt : 25 mg/L SDBS : 25 mg/L POPE.

Research Progress in Blistering Micro-Mechanisms of Organic Coatings

Abstract: With a view to the fact that blistering is one of the most common causes leading to failure of organic coatings, the current state and progress in the research of blistering micro-mechanisms of organic coatings at home and abroad were reviewed. The blistering process of various organic coatings was analyzed, while the failure behaviors of various organic coatings were interpreted with respect to osmotic blistering, anodic blistering, cathodic blistering, stress blistering, and electro-endosmosis blistering.

Electroless Silver Plating on Surface of Carbon Fiber

Abstract: To prepare a new passive jamming material and simplify the technical process, the process of electroless silver plating on surface of carbon fiber was directly studied using glucose and tartaric acid as the reducing agent, the influences of pretreatment of carbon fiber and confection method of solution to the plating result were discussed The electrical conductivity wasalso measured The results showed that the Ag deposit had better uniformity, higher adhesion and lower bulky electrical resistance

Application and Research Development of Erosion Resistant Coating of Compressor Blade

Abstract: Recent applications and research of erosion resistant coating of compressor blade are summarized. Multi-components and multi - layers are effective methods to improve the properties of erosion resistant coating. The future devel- oping trend of erosion resistant coating of compressor blade is expected.

Stress Corrosion-Induced Cracking of 20 Steel in H_2S Solution

Abstract: The stress corrosion-induced cracking(SCC) of 20 steel in saturated H2S solution and its protection were studied using electrochemical polarization,slow strain rate tensile test and applied potential methods.The results showed that 20 steel had high SCC sensitivity in saturated H2S solution.The SCC sensitivity of the 20 steel could be reduced by applying anodic or cathodic polarization,and the anodic polarization was more effective than cathodic polarization in preventing the 20 steel from stress corrosion-induced cracking.Besides,it was feasible to remarkably reduce the sensitivity to SCC of 20 steel by introducing imidazoline or pridinium-sulfourea as inhibitor in the saturated H2S solution.

Preparation of Nanocrystalline Nickel Coating by Pulse Jet-Electrodeposition

Abstract: Nanocrystalline nickel coatings were prepared by pulse jet-electrodeposition.Scanning electron microscopy(SEM),transmission electron microscopy(TEM),and X-ray diffraction(XRD)were used to investigate the morphology and microstructure of the electrodeposited Ni coatings.The influence of current density on the microstructure such as average grain size and texture of Ni coatings was studied as well.The results showed that the inner layer(next to the substrate)of the nickel coatings was composed of more fine grains as compared to the outer layer(next to the bath solution),implying that the metallic grains experience a gradual coarsening with increasing thickness of the coating during the growth process.Moreover,an increase in the pulse peak current density from 45 A/dm2 to 180 A/dm2 resulted in a change in the preferential orientation from a(111)texture to a strong(220)texture,while the average grain size of the nickel coatings decreased with increasing current density from 45 A/dm2 to 120 A/dm2.However,the average grain size of the nickel coatings slightly increased as the current density reached 180 A/dm2.

Effects of Rare Earth Elements on the Corrosion Property of AZ31 Magnesium Alloy

Abstract: The rare earth cerium and neodymium were added in AZ31 magnesium alloy to improve its corrosion resistance. The corrosion behaviors of such alloy were measured through salt spray test and potentiodynamic polarization test. The surface of specimens was observed by using Nikon990 digital camera, Polyvar-MET optical microscope with VSM2000 quantitative analysis system and JEOL scanning electron microscopy. The potentiodynamic polarization curve was measured by using Solartron 1287 poten-tiostat system with a scanning rate of 5 mV/s. The data were collected and analyzed using Corrware and Corrview software. The results showed that the corrosion rate of alloys with Ce or Nd ad-dition decreased about a half in the salt spray test. And the corrosion electrical current also decreased to 0. 12 μA/cm2 and 0. 10 μA/cm2, being less than half of the compared AZ31 alloy (0. 30 μA/cm2). The rare earth Ce and Nd could improve the corrosion resistance of solid solution α(Mg) and make the second phase (3 (Mg17Al12) compound dispread more uniformly, so the corrosion resistance of AZ31 alloy was increased due to the addition of the rare earth element.

Improvement of Adhesion of Direct Copper Plating Layer from HEDP Bath

Abstract: In order to improve the adhesion between iron and copper plating from 1-hy-droxy ethylidene-1,1-diphosphonic acid( HEDP) bath, the ca-thodic polarization curves and potential-time curves were recorded, and the critical initial current density and the quantitative result of adhesion between substrate and copper plating were measured through bend-snap method. The effects of assistant complexing agent and some technological parameters were discussed on the adhesion. The results showed that the addition of the assistant complexing agent increased the cathodic polarization of copper solution, and decreased the critical current density. When copper plating at a constant current density of 1 A/dm2, the surface of iron was activated before the copper deposition, thus the adhesion between iron substrate and copper plating was increased to 6 416. 38 N/cm , which was close to the level of copper plating layer on copper. The quantitative testing of adhesion between substrate and plated layer was introduced, and the potential activation mechanism for the improvement of the adhesion of layer was discussed.