Decrease In Corrosion Rate Research Articles

A Superior Corrosion Protection of Mg Alloy via Smart Nontoxic Hybrid Inhibitor-Containing Coatings.

The increase of corrosion resistance of magnesium and its alloys by forming the smart self-healing hybrid coatings was achieved in this work in two steps. In the first step, using the plasma electrolytic oxidation (PEO) treatment, a ceramic-like bioactive coating was synthesized on the surface of biodegradable MA8 magnesium alloy. During the second step, the formed porous PEO layer was impregnated with a corrosion inhibitor 8-hydroxyquinoline (8-HQ) and bioresorbable polymer polycaprolactone (PCL) in different variations to enhance the protective properties of the coating. The composition, anticorrosion, and antifriction properties of the formed coatings were studied. 8-HQ allows controlling the rate of material degradation due to the self-healing effect of the smart coating. PCL treatment of the inhibitor-containing layer significantly improves the corrosion and wear resistance and retains an inhibitor in the pores of the PEO layer. It was revealed that the corrosion inhibitor incorporation method (including the number of steps, impregnation, and the type of solvent) significantly matters to the self-healing mechanism. The hybrid coatings obtained by a 1-step treatment in a dichloromethane solution containing 6 wt.% polycaprolactone and 15 g/L of 8-HQ are characterized by the best corrosion resistance. This coating demonstrates the lowest value of corrosion current density (3.02 × 10-7 A cm-2). The formation of the hybrid coating results in the corrosion rate decrease by 18 times (0.007 mm year-1) as compared to the blank PEO layer (0.128 mm year-1). An inhibitor efficiency was established to be 83.9%. The mechanism of corrosion protection of Mg alloy via smart hybrid coating was revealed.

Microstructure and corrosion properties of CoCrCuFeMnNix high‐entropy alloys prepared by powder metallurgy

AbstractCoCrCuFeMnNix (x = 0.5, 1.0, 1.5, 2.0 mol, named Ni0.5, Ni1.0, Ni1.5, and Ni2.0, respectively) high‐entropy alloys (HEAs) were prepared by powder metallurgy. The effects of Ni content on its microstructure and corrosion resistance in a 3.5% NaCl solution were studied. The HEAs with low Ni content consisted of FCC1 primary phase, FCC2 secondary phase, and a few σ phases. While the Ni2.0 alloy was composed of the FCC phase and a small amount of σ phase. The results of polarization corrosion in 3.5% NaCl solution show that the increase of Ni content led to the increase of corrosion potential of the alloy and the decrease of corrosion current density and average corrosion rate. Among them, Ni2.0 alloy had the best corrosion resistance. The electrochemical impedance spectroscopy analysis showed that the increase in Ni content promoted the increase of the polarization resistance of the alloy RCPE and the thickness of the passive film, thus improving the corrosion resistance of the alloys.

Evaluating corrosion resistance of recycled aggregate concrete integrating ground granulated blast furnace slag

By understanding the importance of recycled aggregates in the development of sustainable environment, the present study investigated the corrosion performance of recycled aggregate concrete. Since the water to binder ratio has a substantial impact on the performance of concrete, corrosion studies was conducted on a wide spectrum of water to binder ratio varying from 0.25 to 0.75 at 0.1 intervals. In addition, the impact of 50 % ground granulated blast furnace slag on corrosion performance was investigated for the same range of water to binder ratio. For all these developed concretes, coarse natural aggregates were totally replaced with coarse recycled aggregates and their corrosion performance was explored through surface resistivity test, accelerated carbonation test, rapid chloride migration test, half-cell potential, and corrosion rate test. From the results it can be concluded that the inclusion of ground granulated blast furnace slag into the recycled aggregate concrete mix 1) achieved 70 MPa compressive strength in 90 days of curing 2) increased the surface resistivity to 88 kΩcm and 3) decreased the carbonation resistance. By accessing the real time corrosion resistance of steel inside the concrete, an increase in potential and decrease in corrosion rate was observed for ground granulated blast furnace slag based concrete. Hence, it can be concluded that the inclusion of ground granulated blast furnace slag in the recycled aggregate concrete mixes increased the corrosion resistance.

Mild steel corrosion control through locally sourced calcium oxide on zinc phosphating process

Mild steel is vulnerable to corrosion, so its prevention is essential in order to sustain its wide applications in petroleum, food, electrical, chemical, and construction industries. This study investigated the corrosion control action of the locally sourced calcium oxide on the zinc phosphating process of mild steel. Varied concentrations of calcium oxide (0 – 2 g/L) and coating (phosphating) time (40–70 min) were considered during the phosphating of the pretreated mild steel samples at coating temperatures of 60 °C and 80 °C. The phosphate samples were subjected to weight loss tests utilizing a solution of NaCl (3.5 wt.%) at 25 °C, in order to determine both the sample corrosion rates and corrosion inhibition efficiencies. As both the calcium oxide concentration and phosphating temperature increased, the results trend (in general) showed a decrease in corrosion rate and increase in inhibition efficiency. Sample with the operating conditions of 70minutes coating time, 2.0 g/L calcium oxide in the bath at 80 °C coating temperature exhibited the best inhibition efficiency of 81% and lowest corrosion rate of 0.029 mm/year. SEM analysis revealed that the crystals of the coated surface became finer and had a more surface coverage owing to the increase in the concentration of calcium oxide (from 0.7 to 2.0 g/L). ΔGads values of close to -20 kJmol−1 obtained (from both Langmuir and Freundlich adsorption isotherms) revealed a spontaneous and physical adsorption process of calcium oxide on the sample surfaces. The calculated positive values of ΔHads and ΔSads established the phosphating (coating) process to be an endothermic process with increased randomness at the solid/liquid interface of the sample surface and bath solution.

Study of 2-Amino-2-Methyl-1-Propanol Effect on Corrosion of Boiler Low Carbon Steel Pipes in Presence of Sodium Sulfite

This paper studies the effect of 2-Amino-2-mthyl-1-propanol (C3H11NO) on corrosion behavior of boiler steel pipes with low carbon content at sodium sulfite (Na2SO3) in the additive mixtures form as oxygen scavengers in the boiler feed water. 
 Experiments were done at temperatures (100 - 150) ºC and pressures (5 - 9) × 101.3 KN/m² in cylinder autoclave with 7.4 ppm dissolved oxygen in used water, then the corrosion rate is measured by weight loss technique and the concentration of dissolved oxygen in feed water was determined before and after the experiment by Winkler method (Titration). 
 This analysis can provide valuable information for mixture scavengers and corrosion behavior on boiler steel pipes with range of used temperature and pressure. The better ratios found is 60 ppm for every one of amine and sulfite, with the best result in decreasing corrosion rate in acceptable way. The above mentioned ratio is optimal and recommended. This opens up the field for formulation synergetic packages of additives as O2 scavengers. 
 Keywords: Oxygen Scavenger, Na2SO3, C3H11NO, Boiler Steel Pipes, NA-Sulfite & 2-Amino-2-mthyl-1-propanor Additive Package

Implication of nano-scale grain refinement on the passive film formation and corrosion response of AISI 301L steel with and without pre-existing martensite

In this study, the implication of nano-scale grain refinement on corrosion behavior in 301L metastable austenitic stainless steel was investigated. The as-received sample, containing pre-existing martensite, was 87 % cold deformed and reversion annealed at 750 °C for 2 min. A comparative study was also conducted for its fully austenitized counterpart with an identical schedule. Microstructural observations showed deformation-induced martensite transformation during cold rolling, and austenite nano-grains (340–720 nm) formation during reversion annealing. The obtained nano-grains are bimodal and unimodal types for the specimen with and without pre-existing martensite, respectively. Potentiodynamic polarization test revealed about 7 times and 3 times decrease in corrosion rate for the bimodal and unimodal structures, respectively. Moreover, electrochemical impedance spectroscopy and Mott-Schottky analysis indicated the formation of a thick and less defective passive film for the unimodal nano-grained structure. Thus, the present study suggests that grain refinement to the nano range and avoidance of the martensite in the initial structure can substantially improve the corrosion response of 301L stainless steel.

Corrosion and Corrosion Protection of Copper Sculptures by Formation of Composite Barrier

Nitrogen dioxide, carbon dioxide and sulphur dioxide are acidic gas and they produce corrosive medium for copper sculptures. These gases absorb moisture to form nitric acid, carbonic and sulphuric acid. It forms corrosion cell on the surface of copper and accelerate corrosion reactions. The corrosion cell formation is written as: Cu|Cu2+||H+|H2 thus corrosion reactions start and copper is oxidized into Cu2+surface and it is oxidized into Cu2+ whereas H+ ion is reduced into H2 . Nitric acid environment copper exhibits galvanic, pitting, stress, crevice, blistering, embrittlement and intergranular corrosion. The corrosion reactions change physical, chemical and mechanical properties of corroded materials. Nanocoating compound tetrahydrodibenzo[a,d][7]annulene-5,11-disemicarbazone and SiC electrospray compounds used to control the corrosion of copper in nitrogen dioxide medium. For corrosion mitigation of copper metal interface was coated with tetrahydro-dibenzo[a,d][7]annulene-5,11-disemicarbazone and SiC. The coating compound tetrahydro-dibenzo[a,d][7]annulene-5,11-disemicarbazone was synthesized in laboratory. Nozzle spray techniques used for nanocoating and electrospraying. The corrosion rate of copper was determined by gravimetric loss method at different temperatures, concentrations and days in nitrogen dioxide medium. Potentiostatic polarization technique used for the determination of electrode potential, corrosion current and current density. Nanocoating and electrospraying compounds formed a composite barrier on the surface of base metal by chemical bonding. The nanocoating and electrospray compounds adhered on base metal by chemisorptions to confirm by activation energy, heat of adsorption, free energy, enthalpy and entropy. The nanocoating and electrospray deposited on copper confirmed by Langmuir, Frundlich and Temkin isotherm. Copper formed a complex compound to interact with tetrahydro-dibenzo[a,d][7]annulene-5,11-disemicarbazone and SiC. Electrospraying SiC blocked porosities of nanocoating compound and checked osmosis process of nitrogen dioxide. Thenanocoating and electrospray compounds decreased corrosion rate and increased surface coverage areas and percentage coating efficiencies.

The Influence of Thermo Mechanical Treatment on Corrosion Resistance of Cu-Al-Ni Shape Memory Alloy

In This Study that includes the thermal treatment with mechanical in compression at constant loading of 30 KN Was investigated by using the three Different temperature at (260-280-300)°C for Cu-14%Al-4.5Ni then Potentiondynamics polarization tests were applied to the Alloys with Microstructure by Scanning Electron Microscope SEM results shows an decrease in corrosion rates and increasing in corrosion resistance with the Increase of working temperature.

Application of ginger and grapefruit essential oil extracts on the corrosion inhibition of mild steel in dilute 0.5 M H2SO4 electrolyte

Admixture of ginger and grapefruit essential oils (GPP) were studied for their corrosion inhibition properties on mild steel (MS) in 0.5 M H2SO4 solution by potentiodynamic polarization, open circuit potential measurement, electrochemical impedance spectroscopy, weight loss analysis and ATF-FTIR spectroscopy. Results from potentiodynamic polarization shows GPP significantly reduced the corrosion of MS from 8.430 mm/y at 0% GPP concentration to values between 1.979 mm/y and 0.565 mm/y. The corresponding inhibition efficiency values ranged from 76.52% to 93.5% and corrosion current density from 1.88 × 10−4 A/cm2 to 5.36 × 10−5 A/cm2. GPP displayed mixed-type inhibition at all GPP concentrations studied. The OCP plot at 0% GPP initiated at -0.495V compared to -0.443V and -0.451V at 1% and 3.5% GPP. At 9000s, the corresponding OCP values are -0.442V, -0.410V and -0.424V due to electropositive plot shift and passivation of MS surface at 1% and 3.5% GPP, though significant potential transients were present on the OCP plot at 1% GPP. The electrochemical impedance results indicate that the corrosion resistance of MS increased from 4.402 Ω cm2 to 99.318 Ω cm2 upon the addition of 3.5% GPP resulting in inhibition efficiency of 96%. Data from weight loss analysis shows decrease in corrosion rate from 184.48 mm/y to values between 8.94 mm/y and 6.25 mm/y. The corresponding inhibition efficiency values varies from 95.16% at 1% GPP to 96.61% at 3.5% GPP concentration. The ATF-FTIR results confirm the adsorption of GPP molecules on the surface of the carbon steel electrode.

Synthesis and Study Behavior of Some New Pyridinium Salts as Corrosion Inhibitors for Mild Steel in 1M H2SO4

Some new pyridinium bromide derivatives inhibitors, namely;1-benzyl-4-{N-[(4-hydroxyphenyl) methylidene] hydrazinecarbonyl)pyridine-1-ium bromide, A1; 1-benzyl-4-{N-[(4-ethoxyphenyl)methylidene]hydrazine carbonyl}pyridine-1-ium bromide, A2; 1-benzyl-4-{N-[(4-propoxyphenyl) methylidene] hydrazinecarbo-nyl}pyridine-1-ium bromide, A3; were synthesized and studied as inhibitors corrosion for meld steel in 1M H2SO4solution at room temperature via loss of weight measure ementsfor 24 hours. The results showed that inhibition for all pyridineumbromide derivatives have high values with the high concentrate. Increase in inhibition concentrate with corrosion rate decreases, inhibitor increasing and surface coverage degree increases. The free energy value of revealed physisorption effects for (A1, A2, and A3) and gave useful information to predict the interaction nature between the surface of metal and the organic molecules as corrosion inhibitors.

Development of biodegradable in situ Zn-Mg2Sn composites for bone-implant applications

Biodegradable in situ Zn-xMg2Sn composites were prepared via alloying with different Mg2Sn contents and hot-rolling for bone-implant applications. The results indicate that the hot-rolled composites showed increased mechanical strength, hardness, wear resistance, and decreased corrosion rates with increasing Mg2Sn content. Zn-7.5Mg2Sn exhibited the best mechanical property matching, including an ultimate tensile strength of 240.2 MPa, yield strength of 222.0 MPa, elongation of 16.8 %, and hardness of 93.8 HV. Zn-10Mg2Sn showed the lowest degradation rate (22.7 μm/y) among all hot-rolled composites. Furthermore, a 12.5 % concentration of Zn-7.5Mg2Sn extract showed no cytotoxicity toward 3 T3 cells. Overall, the Zn-7.5Mg2Sn composite is proposed as a promising candidate for biodegradable bone-implant material.

Analysis of the structural integrity of (Si3N4 and Al2O3) individuals coatings and the [Si3N4 /Al2O3]n heterostructure exposed to corrosive environments

In order to study the corrosive wear presented in the (Si3N4 and Al2O3) individual layers and the [Si3N4/Al2O3]n heterostructure as a function of the bilayers number (n = 1, 10, 30 and 70), exposed to a highly aggressive environments. This research presents a exhaustive analysis of the structural, chemical and surface properties, which influenced the corrosion response of these coatings. The results showed that the heterostructure presented better properties than the individual coatings, and that when the bilayers number increased, these properties also increased. Thus, the [Si3N4/Al2O3] heterostructure formed by 70 bilayers, presented values of 4.1 nm, 161 nm and 1.79% approximately for roughness, grain size and porosity factor, respectively, which represents a decrease of 51%, 82% and 23% of these properties in comparison to the heterostructure formed by 1 bilayer. Finally, these structural and surface conditions resulted in a 90% increase in polarization resistance and a 95% decrease in corrosion rate when comparing the n = 70 bilayers heterostructure with the n = 1 bilayer. Concluding that the [Si3N4/Al2O3] heterostructure formed by 70 bilayers presented the best set of properties to be implemented in highly corrosive environments.

Effect of Chitosan on the Corrosion Inhibition for Aluminium Alloy in H2SO4 Medium

Aluminum AA5052 is an inexpensive and lightweight metal that has been used in a variety of applications, including the Bipolar Plate in Proton Exchange Membrane Fuel Cells (BPs PEMFC). The alloy has good electrical conductivity and low corrosion. Corrosion rate (CR) increases during PEMFC operation with increasing temperature. Inorganic dyes, such as chromate, are commonly used to reduce metal corrosion. Unfortunately, they are toxic and have a negative impact on the environment. Chitosan, which is a green, cheap, non-toxic, and environmentally friendly organic solvent, can be used to solve this problem. Electrophoretic Deposition (EPD) technique was used to coated the surface of AA5052 with chitosan. CR was measured using electrochemical and weight loss methods (in 0.5 M H2SO4). The best research results are as follows. The lowest CR values were obtained at the EPD time of 20 min at a chitosan concentration of 0.5% wt. The results of the study using the weight loss method indicated that after soaking for 72 h, the chitosan inhibitor can reduce the corrosion rate (CR) with an inhibitor efficiency of 87.89%, while the electrochemical method obtained a higher efficiency of 95.12%. An increase in temperature will result in a decrease in the efficiency of the inhibitor. Testing with SEM-EDX, after being coated with chitosan inhibitor, the metal surface looks smoother and the Al composition is reduced and it is detected that there is adsorption of O, N and S elements that coated the metal to form insoluble complex compounds, so the corrosion rate decreases.

L-Ascorbic Acid as an Efficient Green Corrosion Inhibitor of Steel Rebars in Chloride Contaminated Cement Mortar.

Corrosion of reinforcement is a major problem regarding concrete durability. In new structures the corrosion onset can be delayed if additional protection methods are provided as is the case for the addition of corrosion inhibitors in the concrete mix. The main goal of this paper is the evaluation of the effect of the ascorbic acid (AA) as a green steel corrosion inhibitor in cement mortars contaminated by chlorides. Concentration levels of ascorbic acid, ranging from 0.5 to 10-3 mol/L, were added to the mixing water. Electrochemical methods, including corrosion potential (Ecorr), linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS), were employed to assess the corrosion rate of the steel embedded in the mortars. The corrosion inhibiting performance of ascorbic acid was compared with that of sodium nitrite. The interaction of the ascorbic acid with the hydrated cement matrix was also evaluated with differential thermal and thermogravimetric analysis (DTA/TG) and pH measurements. The results indicated that, depending on the ascorbic acid concentration, it can be an activator of the corrosion process or an effective corrosion inhibitor in a similar manner to sodium nitrite. A corrosion rate decrease was achieved with concentrations below 10-2 mol/L and the optimum content was 10-3 mol/L. Within this concentration range, the AA does not modify the hydration performance of the cement matrix.

The effect of bird droppings on the corrosion of steel and aluminum used in offshore applications

AbstractEngineering materials in service are frequently exposed to bird droppings (BDs). In this study, the interaction has been studied of BDs from chicken with a carbon steel, AISI 316, 22% Cr duplex stainless steel (DSS), 25% Cr super duplex stainless steel (SDSS), carbon steel with a thermally sprayed aluminum (TSA) coating, and aluminum alloy EN AW 6082. Samples with and without BDs are exposed to a cyclic salt spray test for up to 692 h (29 days). Electrochemical experiments in the presence of BDs were conducted in a syringe‐based droplet cell. Characterization of the corrosion products by infrared (IR) and Raman spectroscopy shows no build‐in of organic components into the corrosion products in the samples exposed to BDs. In general, BDs affect the anodic dissolution mechanism of metals and increase the critical pitting potential. For carbon steel, a component of the BDs acts as an anodic inhibitor, leading to passivation of the surface and decreasing corrosion rates by 1–2 orders of magnitude. For 316, BDs increase the critical pitting potential but may facilitate crevice‐like initiation of localized corrosion. There are negligible effects of BDs on the corrosion of SDSS, and no evidence either for adverse effects on DSS. TSA shows an increased corrosion rate by half to one order of magnitude with BDs, but its ability to galvanically protect a steel base material is not compromised. AW 6082 shows decreased corrosion rate, no difference in mass loss, but increased pitting in the presence of BDs. Overall, these model experiments may only be seen as the start of a more systematic understanding of the interaction of BDs with engineering materials.

Effect of Stray Current on Corrosion and Calcium Ion Corrosion of Concrete Reinforcement.

The construction of subways, hydroelectric stations and water substations is exposed to stray currents, which can accelerate concrete corrosion. The influence of stray currents on reinforced concrete structures is unclear. In this paper, the influence of concrete strength grade, reinforcement diameter and stray current intensity on the extent of reinforcement corrosion and calcium ion dissolution were investigated, and the damage of reinforcement and calcium ion corrosion to concrete strength was investigated by simulating a stray current environment and conducting an electrified acceleration test. The test results show that the higher the strength grade of concrete, the lower the stray current intensity and the smaller the corrosion rate and calcium ion dissolution rate of reinforcement; with the increase in the diameter of reinforcement the corrosion rate decreases, but the calcium ion dissolution rate is not affected by reinforcement diameter. The damage effect of reinforcement corrosion on concrete compressive strength is more obvious than that of calcium ion corrosion.

The Spontaneous Repassivation of Cr Containing Steels and Multi-Principal Element Alloys

The corrosion resistance of an alloy in most environments will depend on its ability to spontaneously passivate at the corrosion potential. This is especially true for localized forms of corrosion such as occur in acidic, occluded environments during pitting and crevice corrosion. In the laboratory however, the kinetics of passivation are mainly investigated using electrochemical methods that require polarization of the material via an external power source. Spontaneous passivation cannot directly be observed by this approach. It is therefore of interest to investigate the repassivation phenomena as it occurs at open circuit, driven by the oxidizing agents present in the electrolyte.To this end, we have recently developed a methodology to determine the kinetics of spontaneous passivation using element-resolved electrochemistry (atomic spectroelechemistry, or ASEC) [1-3]. Passivation may be measured by first disrupting the original passive film using an electrochemical perturbation and then monitoring the corrosion rate as a function of time on an element-by-element basis. As the passive film reforms, the corrosion rate decreases allowing a real time monitoring of film formation. The perturbation may be either a cathodic pulse to reduce the passive film as in a conventional polarization curve experiment, or it may be an anodic pulse into the transpassive domain.In addition, the contribution of the individual alloying elements to dissolution and to passive film formation may be quantitatively accessed thereby yielding insight into one of the fundamental questions for engineering new alloys - what is the specific role of the different alloying elements? For example, it is widely recognized that for the Cr containing alloys, Cr is the primary constituent of the passive film, at least when Cr is above about 12%. However, the presence of other elements may affect the efficiency of Cr-oxide film formation, some like Mo in a beneficial way [2], others like Mn in a negative way [3]. Via a simple mass balance, the elemental dissolution rate profiles may be transformed into a time resolved elemental surface enrichment profile. This allows a direct look into the role of the alloying elements.The Figure gives an example of this approach based on the results from Ref. 3. The system under investigation was the high entropy Cantor alloy containing alloyed nitrogen in a sulfuric acid solution. The left-hand side gives the open dissolution rate for an experimental sequence of (a) open circuit, (b) cathodic activation (300 s at -0.8 V vs. SCE), (c) repassivation at open circuit (300 s). Repassivation is indicated by the initially large corrosion rate (active state) followed by the decrease of the corrosion rate as the passive film reforms. The contribution of the individual alloying elements is shown all of which dissolved congruently with the exception of Cr which was below the congruent level (black line) indicative of Cr surface enrichment. The right hand side gives the quantity of Cr enriched on the surface during the sequence calculated by mass balance. Cr dissolves during the cathodic activation but reforms as soon as the potential is released. Also shown is the Cr enrichment during an anodic step to 0.4 V which leads to a more rapid and significant build-up of surface Cr.This presentation will review the methodology of spontaneous passivation measurements for both austenitic stainless steel (304L) and for the high entropy Cantor alloy (equimolar NiFeCrCoMn) with variable Mn content. In particular, we will focus on the differences between repassivation following cathodic activation and transpassive activation. The mechanisms of spontaneous repassivation will be discussed with an emphasis on how the alloying elements influence repassivation under these two conditions.1) K Ogle “Atomic emission spectroelectrochemistry: real-time rate measurements of dissolution, corrosion, and passivation”, Corrosion 75 (2019)1398-1419. Open access. 2) X Li, J D Henderson, F P Filice, D Zagidulin, M C Biesinger, F Sun, B Qian, D W Shoesmith, J J Noël, K Ogle, “The contribution of Cr and Mo to the passivation of Ni22Cr and Ni22Cr10Mo alloys in sulfuric acid”, Corrosion Science 176, (2020) 109015.3) X Li, P Zhou, H Feng, Z Jiang, H Li, K Ogle, “Spontaneous passivation of the CoCrFeMnNi high entropy alloy in sulfuric acid solution: The effects of alloyed nitrogen and dissolved oxygen”, Corrosion Science 196(2022)110016. Figure 1

Fretting corrosion behavior of WC-10Co-4Cr coating on Inconel 690 alloy by HVOF thermal spraying

WC-10Co-4Cr coating was deposited through supersonic flame of high-velocity oxygen fuel (HVOF) process on the outside surface of Inconel 690 alloy tube. The fretting corrosion behavior of substrate- and coating- treated alloy tubes under dry state and seawater are compared. Results show remarkable differences between substrate- and coating-treated samples in electrochemical corrosion response and wear behavior. The fretting wear resistance of the WC-10Co-4Cr coating-sprayed alloy tube considerably improved because its surface mechanical properties are better than that of the substrate. Though the initial static corrosion performance of the coating is poorer than the substrate alloy tube, its excellent wear resistance helps decrease corrosion rate. In addition, the predominant damage mechanism of fretting corrosion was abrasive wear, fatigue delamination, and corrosion.

Corrosion behavior of Ti60 alloy under continuous NaCl solution spraying at 600 °C

• The corrosion rate of Ti60 alloy in NaCL spray is lower than that under NaCL film. • A mixed corrosion including classical oxidation and active oxidation happened. • The mixed corrosion delayed active oxidation and formed dense Ti oxides scale, both of which decreased corrosion rate. The corrosion behavior of Ti60 alloy was investigated under continuous NaCl solution spraying at 600 °C. Results indicate that the corrosion rate of the Ti60 alloy is lower than that obtained with the solid NaCl deposit film in H 2 O + O 2 . The outer corrosion products are compact layers mainly containing Na 2 TiO 3 and nanocrystalline TiO 2 . The inner layer is mainly composed of Ti 2 O, TiO and SnO 2 . Ti 2 O has a lamellar structure, and TiO has a strip-shaped structure. A mixed corrosion mechanism including classic oxidation and active oxidation occurred under NaCl solution spraying environment: the first stage was controlled by the classic oxidation mechanism with the promotion by the active oxidation following parabolic curves, and the second stage was controlled by the active oxidation mechanism following a linear rise in the mass gain curve. The mixed corrosion mechanism between classic oxidation and active oxidation produced a relatively dense Ti oxides scale, which decreased the corrosion rate.

Modification Structure and their Effects on Physical Properties of Tin Based Lead Free Solder Alloys for Industrial Applications

Soldering properties such as melting temperature and wettability of tin-zinc alloy improved after adding different alloying elements such as indium, aluminum, cadmium and bismuth. Decreasing zinc content (Sn91Zn9) up to 4% (Sn96Zn4 alloy) increased corrosion resistance from -0.847 to -0.530 and decreased corrosion rate from 51.84 to 7.705 mpy. Microstructure of tin-zinc alloy changed with increasing hardness value of it after adding alloying elements. Tin-zinc alloys have lower melting temperature compared to Sn95Sb5, Sn96.5Ag3.5 and Sn99.3Cu0.7 alloys. The Sn90Zn4Bi6 alloy has beast solder properties for electronic industrial applications.