Study on metal corrosion caused by chlorine dioxide of various purities

Weight lost method was used to comparatively study the corrosion behavior of four different metals under the dosage of chlorine dioxide, chlorine and their mixture respectively. The experimental results indicated that chlorine causes the most serious corrosion of carbon steel, and the higher the concentration of chlorine, the more serious the corrosion. On the contrary, metals corrosion is the least serious in the case of chlorine dioxide. The results further revealed that chlorine dioxide is the most effective water treatment reagent, making it the best choice to use extensively in circulated cooling water disinfection and corrosion control.

Effect of Salt Spray Corrosion on Tribological Properties of HVOF Sprayed NiCr-Cr3C2 Coating with Intermediate Layer

The objective of the present work was to determine the influence of the neutral salt spray corrosion on the wear resistance of HVOF sprayed NiCr-Cr3C2 coating with intermediate layer. Ni-Zn-Al2O3 coatings as interlayers were prepared by low pressure cold spray（LPCS） between NiCr-Cr3C2 cermet coatings to form a sandwich structure to enhance the corrosion resistance properties. The tribological properties were examined using the UMT-3 fricition and wear tester by line-contact reciprocating sliding under dry and salt spray one week corrosion. The morphology, element distribution, and phase compositions of the coating and worn sufaces were analyzed by using scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction respectively. The corrosion behavior of the coating was studied by the open-circuit potential, the electrochemical impedance spectroscopy, potentiodynamic polarization, and salt spray corrosion methods. It is found that the sandwich structured coating has better corrosion resistance than the single layer coating. The results show that under dry wear conditions, the wear mechanism is abrasive and adhesive wear, whereas under salt spray corrosion conditions it becomes corrosion wear. The friction coefficient of the sandwich structured coating after salt spray corrosion is slightly lower than the dry friction coefficient, but the weight of the wear loss is lower than that under dry condition.

High plastic Zr–Cu–Fe–Al–Nb bulk metallic glasses for biomedical applications

Four Zr–Cu–Fe–Al-based bulk metallic glasses（BMGs） with Zr contents greater than 65at% and minor additions of Nb were designed and prepared. The glass forming abilities, thermal stabilities, mechanical properties, and corrosion resistance properties of the prepared BMGs were investigated. These BMGs exhibit moderate glass forming abilities along with superior fracture and yield strengths compared to previously reported Zr–Cu–Fe–Al BMGs. Specifically, the addition of Nb into this quaternary system remarkably increases the plastic strain to 27.5%, which is related to the high Poisson＇s ratio and low Young＇s and shear moduli. The Nb-bearing BMGs also exhibit a lower corrosion current density by about one order of magnitude and a wider passive region than 316 L steel in phosphate buffer solution（PBS, pH 7.4）. The combination of the optimized composition with high deformation ability, low Young＇s modulus, and excellent corrosion resistance properties indicates that this kind of BMG is promising for biomedical applications.

STRUCTURE OF BLACK PATINA ON THE ANCIENT BRONZE MIRRORS

X-ray diffaction analysis(XRDA)data of the black or brown patina on the surfaces of eight kinds of bronze mirror samples show 4 or 5 broad diffuse peaks which corresponding to almost the same 20 angle, while their matixes does not.These results indicate that those diffuse peaks were produced by the SnO2, microcrystals of 3 ￣5 nm size contained in the black or brown patina.The matrix of unearthed black patina bronze mirror numbered 223, gives strong XRDA diffraction peaks, indicating that there are a large amounts of non-oxidized bronze alloy particles surrounded by SnO2,which shows that the black patinas are not wholly metallic oxides (mainly SnO2),there are also a lot of original alloys of different sizes in grain in the patina.The bright-field image of the black patina sample gives the same result.

Corrosion behavior of metallic alloys in molten chloride salts for thermal energy storage in concentrated solar power plants： A review

Recently, more and more attention is paid on applications of molten chlorides in concentrated solar power （CSP） plants as high-temperature thermal energy storage （TES） and heat transfer fluid （HTF） materials due to their high thermal stability limits and low prices, compared to the commercial TES/HTF materials in CSP- nitrate salt mixtures. A higher TES/HTF operating temperature leads to higher efficiency of thermal to electrical energy conversion of the power block in CSP, however causes additional challenges, particularly increased corrosiveness of metallic alloys used as contain- ers and structural materials. Thus, it is essential to study corrosion behaviors and mechanisms of metallic alloys in molten chlorides at operating temperatures （500-800℃） for realizing the commercial application of molten chlorides in CSE The results of studies on hot corrosion of metallic alloys in molten chlorides are reviewed to understand their corrosion behaviors and mechanisms under various conditions （e.g., temperature, atmosphere）. Emphasis has also been given on salt purification to reduce corrosive impurities in molten chlorides and development of electrochemical techniques to in-situ monitor corrosive impurities in molten chlorides, in order to efficiently control corrosion rates of metallic alloys in molten chlorides to meet the requirements of industrial applications.

Formation of Black Patina on Bronze Mirrors Caused by Multiphenol

Hot solution of hydroquinone is oxidized by air forming quinone and quinhydrone, both of which have weak oxidizeability, enabling to oxidize metals on the surface of bronze mirror samples forming black and brilliant patina. SEM and electron micro probe analysis show that Cu content is lower than that of the original alloy due to Cu loss; Sn content is higher than the original alloy in patina. This indicates that humic acid is not the substance resulting in making black patina on the bronze mirror surface, but the black patina which produced from hydroquinone solution absence of Si, Al and Mg.

Evaluation of morphology and mechanical properties of austenitic stainless steel 316L exposed to high-velocity liquid PbBi at high temperature

In the accelerator driven sub-critical system（ADS） cooled by liquid PbBi alloy,the austenitic stainless steel 316 L is one of the candidates of structural materials.However,the corrosion and wear behavior of 316 L steel in the high-velocity stream of liquid PbBi is the most essential issue,which is urgent to be paid close attention.In order to acquire the morphology and mechanical properties of 316 L steel in the conditions of different relative flowing velocity（RFV）,respectively 2.62 m/s,3.69 m/s,4.77 m/s,the experiment was carried out in dynamic liquid PbBi at 550℃,up to about 1 500 h.According to the results,the surface of 316 L has been corroded badly and the elements of Ni,Cr,etc.were found to dissolve a lot.With the increase of the RFV,the feature of 316 L surface changed from the surface with much deeper pits and looser structures to the relative planar one,and the thickness of the outer oxide layer decreased gradually while that of the inner oxide layer diminished a little,and the microhardness of the outermost substrate also declined increasingly,in addition,the domain of the partial substrate with its microhardness being altered deepened further.These experimental data would offer theoretical basis and practical values to study corrosion condition of 316 L steel in liquid PbBi with high-velocity.

Treatment of mine drainage generated by lead-zinc concentration plant

The purification efficiency in the treatment of the mine drainage generated by the mineral processing industry in Mengzi,Yunnan Project, China, was investigated, and the influences of the treated drainage on the mineral electrodes' electrochemical behaviors were tested. Experiments with different doses of polyacrylamide(PAM) and polymeric ferric sulfate(PFS) at different pH values were carried out, and the advanced purification by activated carbon(AC) was conducted. Compared with PFS, the better coagulant for removal efficiency is PAM, under the optimal conditions, the removals of Pb2+, Zn2+, Cu2+ and COD reduction from solution were 94.8%, 79.9%, 87.6% and 85%, respectively. In the advanced purification, the particle size of activated carbon and agitation time played important roles in the removal efficiency. Each pollute concentration could meet the emission standard of pollutants for lead and zinc industry(GB25466—2010). The wastewater without treatment affected galena and sphalerite electrochemical behaviors greatly, after treatment by the technology, the effects disappeared, which proved the reliability of the technology for wastewater treatment.

Natural Convective Heat and Mass Transfer of Water with Corrosion Products at Super-Critical Pressures under Cooling Conditions

A numerical study is reported of laminar natural convective heat and mass transfer on a vertical cooled plate for water containing metal corrosion products at super-critical pressures. The influence of variable properties at super-critical pressures on natural convection has been analyzed. The difference between heat and mass transfer under cooling or heating conditions is also discussed and some correlations for heat and mass transfer under cooling conditions are recommended.

Role of late transition metals on pitting resistance of Zr-Ti-(Cu, Ni,Co)-Al bulk metallic glasses in 0.6 M NaCl aqueous solution

Four quanternary Zr-based bulk metallic glasses（BMGs）were selected,including the Zr_（46）Ti_2Cu_（45）Al_7,Zr_（61）Ti_2Cu_（25）Al_（12）,Zr_（55）Ti_4Ni_（22）Al_（19）and Zr_（55）Ti_2Co_（28）Al_（15）,due to their robust glass-forming ability and containing a single species of late transition metal（LTM）in compositions.Their pitting resistances in 0.6 M Na Cl aqueous solution were investigated to examine the role of LTM elements in the alloys,with electrochemical measurements,surface morphology observation and x-ray photoelectron spectrometry analysis.It is shown that in comparision with two Cu-bearing BMGs,Zr_（55）Ti_4Ni_（22）Al_（19）and Zr_（55）Ti_2Co_（28）Al_（15）BMGs exhibited significantly superior resistance to pitting.Zr_（61）Ti_2Cu_（25）Al_（12）,Zr_（55）Ti_4Ni_（22）Al_（19）and Zr_（55）Ti_2Co_（28）Al_（15）BMGs manifested distinct passivation behaviour,because of the formation of surface passive film mainly comprising of Zr O_2,Ti O_2and Al_2O_3.However,no significant differences in the electrochemical resistive properties and thicknesses of passive films were found between Zr_（61）Ti_2Cu_（25）Al_（12）and Zr_（55）Ti_4Ni_（22）Al_（19）BMGs.Nevertheless,at the passive film/metal interface,copper enrichment took place in Zr_（61）Ti_2Cu_（25）Al_（12）,whereas the nickel was slightly deficient at the interface in Zr_（55）Ti_4Ni_（22）Al_（19）.During pitting propagation,selective dissolution of the zirconium,titanium and aluminum over the copper took place in Zr_（61）Ti_2Cu_（25）Al_（12）,but it was not the case in Zr_（55）Ti_4Ni_（22）Al_（19）.For the two Cu-bearing BMGs,reduction of passive base metal elements in composition resulted in local selective dissolution,even absence of the passivation.

Natural Convective Heat and Mass Transfer on a Vertical Heated Plate for Water Flow Containing Metal Corrosion Particles

Corrosion products of structural materials when contained in water usually are in two states:soluble state and colloidal particles with diameter about 10^(-3)—10^(-1)μm.Deposits of such corrosion products on tube surfaces under high pressure will jeopardize the operating economy of power plant equipment and even result in accidents. A numerical study is reported in this paper of the natural convective heat and mass transfer on a vertical heated plate subject to the first or mixed kind of boundary conditions for high-pressure water(P=17MPa)containing metal corrosion products with consideration of variable thermophysical properties.

Electrical and Corrosion Properties of Titanium Aluminum Nitride Thin Films Prepared by Plasma-Enhanced Atomic Layer Deposition

Titanium-aluminum-nitride（TiAlN） films were grown by plasma-enhanced atomic layer deposition（PEALD）on 316 L stainless steel at a deposition temperature of 200 °C. A supercycle, consisting of one AlN and ten TiN subcycles, was used to prepare TiAlN films with a chemical composition of Ti（0.25）Al（0.25）N（0.50）. The addition of AlN to TiN resulted in an increased electrical resistivity of TiAlN films of 2800 μΩ cm, compared with 475 μΩ cm of TiN films, mainly due to the high electrical resistivity of AlN and the amorphous structure of TiAlN. However, potentiostatic polarization measurements showed that amorphous TiAlN films exhibited excellent corrosion resistance with a corrosion current density of 0.12 μA/cm^2, about three times higher than that of TiN films, and about 12.5 times higher than that of 316 L stainless steel.

In Vitro Evaluation of the Feasibility of Commercial Zn Alloys as Biodegradable Metals

In this work, three widely used commercial Zn alloys （ZA4-1, ZA4-3, ZA6-1 ） were purchased and pre- pared by hot extrusion at 200℃. The microstructure, mechanical properties, corrosion behaviors, biocompatibility and hemocompatibility of Zn alloys were studied with pure Zn as control, Commercial Zn alloys demonstrated increased strength and superb elongation compared with pure Zn. Accelerated corrosion rates and uniform corrosion morphologies were observed in terms of commercial Zn alloys due to galvanic effects between Zn matrix and α-Al phases. 100% extracts of ZA4-1 and ZA6-1 alloys showed mild cytotoxicity while 50% extracts of all samples displayed good biocompatibility. Retardant cell cycle and inhibited stress fibers expression were observed induced by high concentration of Zn^2＋ releasing during corrosion. The hemolysis ratios of Zn alloys were lower than 1% while the adhered platelets showed slightly activated morphologies. In general, commercial Zn alloys possess promising mechanical properties, appropriate corrosion rates, significantly improved biocompatibility and good hemocompatibility in comparison to pure Zn. It is feasible to develop biodegradable metals based on commercial Zn alloys.

Design of Fe–Mn–Ag Alloys as Potential Candidates for Biodegradable Metals

In this work,a series of biodegradable pure iron,Fe–30Mn and Fe–30Mn–Ag alloys were developed by using a rapid solidification technology.A fine a-Fe dendrite was formed in pure iron,resulting in a high compressive yield strength of above 300 MPa.The Fe–30Mn alloy doped with only 1%Ag exhibited a significant increase in the degradation rate in simulated body fluid due to the precipitation of Ag-rich particles in alloy matrix and the induction of the microgalvanic corrosion.In addition,the novel Fe–30Mn–Ag alloy also exhibited a good magnetic compatibility and offered a closely approaching requirement for biodegradable medical applications.