Minimum Corrosion Rate Research Articles

Effect of CeO2 and graphite powder on the electrochemical performance of Ti/PbO2 anode for zinc electrowinning

In the zinc hydrometallurgy process, the key to reduce the voltage of the corrosion is to reduce the oxygen evolution potential of the anode. In this experiment, the effects of doped CeO2 and graphite powder (GP) on the electrochemical properties of Ti/PbO2 were investigated. Ti/PbO2, Ti/PbO2-CeO2, Ti/PbO2-GP and Ti/PbO2-CeO2-GP anode were prepared by direct current (DC) plating. The surface morphology and composition of these different Ti/PbO2 electrodes before and after polarisation were analysed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion mechanism was analysed by linear sweep voltammetry (LSV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The cell voltage, current efficiency, service life and failure mechanism of Ti/PbO2 anodes were observed and analysed by simulating electrowinning experiments. The results show that Ti/PbO2-CeO2-GP anodes is denser than other electrodes. Ti/PbO2-CeO2 (12 g/L)-GP (8 g/L) with the lowest anode potential is 1.5390 V. The potential of the lowest oxygen evolution peak of the Ti/PbO2-CeO2 (12 g/L)-GP (8 g/L) electrode is 0.824 V. The Ti/PbO2-CeO2-GP anode had a minimum cell voltage of 2.85 V and a current efficiency of 95.8%. The Ti/PbO2-CeO2-GP has a minimum corrosion rate of − 0.0320 g·A−1·h−1 and a longest anode lifetime of up to 127 h. The best electrode for the surface coating is Ti/PbO2-CeO2 (12 g/L)-GP (8 g/L).

Microstructure and corrosion behavior of Al3Ti/ADC12 composite modified with Sr

In this study, we investigated the effect of the addition of Sr (0wt%, 0.1wt%, 0.2wt%, and 0.3wt%) on the microstructure and corrosion behavior of Al3Ti/ADC12 composite by optical microscopy, X-ray diffraction, scanning electron microscopy, and energy diffraction spectroscopy. The results reveal that the α-Al phases were nearly spherical and 40 μm in size and that the eutectic Si phases became round in the composite when the Sr content reached 0.2wt%. The Al3Ti particles were distributed uniformly at the grain boundary. The results of the corrosion examination reveal that the Al3Ti/ADC12 composite exhibited a minimum corrosion rate of 0.081 g·m–2·h–1 for an Sr content of 0.2wt%, which is two thirds of that of unmodified composite (0.134 g·m–2·h–1). This improved corrosion resistance was due to galvanic corrosion, which resulted from the low area ratio of the cathode to anode regions. This caused a low-density corrosion current in the composite, thereby yielding optimum corrosion resistance.

THE CORROSION BEHAVIOR AND WEAR RESISTANCE OF GRAY CAST IRON

Gray cast iron has many applications as pipes, pumps and valve bodies where it has influenced by heat and contact with other solutions . This research has studied the corrosion behavior and Vickers hardness of gray cast iron by immersion in four strong alkaline solutions (NaOH, KOH, Ca(OH)2, LiOH)with three concentrations (1%,2%,3%) of each solution. Dry sliding wear has carried out before and after the heat treatments (stress relief, normalizing, hardening and tempering). In this work, maximum wear strength has obtained at tempered gray cast iron and minimum corrosion rate has obtained in LiOH solution by forming protective white visible oxide layer.

Determining the Minimum Corrosion Conditions for the Stir Zone of Friction Stir Welded AA6061 Aluminium Alloy Joints

Joining of aluminium is commonly done in automobile industries because of its light weight and high specific strength. In recent days, friction stir welding (FSW) is widely preferred to join aluminium than fusion-welding processes. In this joint, grains are very fine in stir zone (SZ) compared to the other zones. Due to this extreme change in the microstructure at the SZ, the mechanical properties (tensile strength, hardness, etc) of the FSW joints are superior but the corrosion resistance of SZ is very poor. The concentration of chloride ion, exposure time and pH value are reported to be the more influencing corrosion test parameters. The present work aims to determine combination of these pitting corrosion test parameters to attain a minimum corrosion rate at the SZ of friction stir welded aluminium alloy, AA6061-T6, by response surface methodology (RSM). From the results obtained, chloride ion concentration is reportedly had higher effect on corrosion rate than the other two parameters considered.

Evaluation of Maximum and Minimum Corrosion Rate of Steel Rebars in Concrete Structures, Based on Laboratory Measurements on Drilled Cores

This paper presents a method of conducting diagnostic tests for corrosion rate in concrete structures, which has been patented by the authors. The method consists in drilling cores with embedded pieces of steel reinforcement from cylindrical structures, and arranging a three-electrode system on such cores to measure polarization with a potentiostat. The three-electrode arrangement uses a piece of steel reinforcement in concrete core as the working electrode, a stainless steel sheet placed on one of the core bases – as the counter electrode, and an electrode of constant and known potential as the reference electrode. Determining the maximum and minimum corrosion rate of a steel bar in the concrete core is the most important element of the developed method, in which changeable temperature and humidity conditions are modelled around the tested structure. Extremely adverse and highly favourable values of temperature and humidity are determined for individual tested structures. Those parameters can be monitored in a climatic chamber while measuring polarization resistance of the reinforcement. This paper also includes examples of practical application of this method in diagnostic tests conducted by the authors on responsible reinforced concrete structures

Effects of waste eggshells and SiC addition in the synthesis of aluminum hybrid green metal matrix composite

Abstract The mechanical behavior, physical behavior, microstructural characteristics, and corrosion behavior of AA2014/silicon carbide (SiC)/carbonized eggshell hybrid green metal matrix composites (MMCs) were investigated. Twenty-five samples of hybrid composite with different combinations of SiC and carbonized eggshell particles in AA2014 matrix alloy were prepared. Microstructure presents that the reinforcement particles (SiC and eggshells) are uniformly distributed in the matrix AA2014 alloy. Transmission electron microscope image shows proper wettability between SiC, carbonized eggshell, and AA2014 aluminum alloy. The tensile strength and the fatigue strength for the composites containing 2.5 wt.% SiC up to 7.5 wt.% carbonized eggshell were observed to be higher than that of the other selected composites. The hardness values for the composites containing 12.5 wt.% SiC and 2.5 wt.% carbonized eggshell were in all cases higher than that of the other composites. The results show that toughness decreases with the increase in the weight ratio of SiC and carbonized eggshell in the composites. The results reveal that the sample of AA2014/2.5% SiC/12.5% carbonized eggshell shows minimum corrosion rate among all the selected samples. Density, porosity, and overall cost of hybrid metal matrix composites were also calculated to see the effects of carbonized eggshell and SiC addition in AA2014 matrix alloy.

Development of Corrosion Resistance Coatings for Sea Water Pipeline

The pipelines that are used for transporting sea water to desalination plants are made of expensive steel alloys. However because of the salt content in water and also other atmospheric factors this pipe undergoes severe corrosion problem. This causes pits and holes in pipe surface making it useless and lead to huge replacement cost of pipes. Hence a way to control corrosion is needed.In this project use of different coatings to overcome corrosion is tested experimentally. Five types of coatings namely epoxy, aluminum, enamel, rubber, and chrome are coated on the samples prepared from actual pipeline used in the plant and the experimental results and analysis are summarized for finding the best coating for reducing corrosion of pipes. Among the five different coatings tested the rubber and epoxy coatings resulted with minimum corrosion rate and weight loss.

The corrosion of X52 steel at an elbow of loop system based on array electrode technology

The corrosion behavior and mechanism of X52 steel at an elbow of loop system based on array electrode technology were investigated to determine the correlation between the corrosion behavior and flow velocity, shear stress and the volume fraction of particles by electrochemical techniques, computational fluid dynamics simulation and surface analysis. The results show that the distribution of corrosion rate is in good accordance with the distribution of the volume fraction of CaSO4 particles at the elbow, and the higher corrosion rate corresponds to the bigger volume fraction of CaSO4 particles. The minimum corrosion rate appears at the innermost side of the elbow, the location with the minimum volume fraction of CaSO4 particles.

Effective Alarm Model Using Non Invasive Corrosion Monitoring for Risk Asssessment of Underground Pipelines

Effective corrosion monitoring can be achieved using mobile potenciostat through the selection of appropriate monitoring methods and special kind of sensor. Stern polarization technique in non-invasive arrangement was used to monitor OCP potential and actual corrosion rate of pipeline with corrosion products in soil mixture. Using global database with range of minimum and maximum corrosion rate limits obtained from terrain measurements we can determine active or passive role of corrosion products and assess risk joint with aggressiveness of soil in location of interest. Finally, values were divided between high active, medium active and passive corrosion. Output is alarm, which can help in decision if reconstruction of underground pipelines where isolation failure in time is sufficient or not. When done properly, corrosion monitoring using non-invasive in-situ technique can serve as an early warning system before the onset of corrosion-related failures.Fig. 1 Non-invasive corrosion monitoring on underground pipelines

Weld Cladding with Austenitic Stainless Steel for Imparting Corrosion Resistance

Weld cladding is a process of depositing a thick layer of a material on a corrosion-, or erosion-, prone material to protect it from corrosion or erosion respectively. In this process, service life of the clad component increases substantially even under hostile conditions. In the present work, austenitic stainless steel cladding is done on low alloy steel specimens to make the clad components resistant to corrosion wearing under a chemically reactive environment. Corrosion-resistance characteristics of clad layer is explored along with its dependency on clad bead geometry, clad composition, etc. that are controlled by process parameters. It is, therefore, essential to select appropriate process parameters to obtain sound clad quality. Experiments are conducted on cladding with austenitic stainless steel on low alloy steel plates under varying conditions using gas metal arc welding. Performance of cladding is experimentally explored to find out suitable parameter combination to obtain high corrosion resistance. At 100 A weld current, 8.7 mm/s torch travel speed and 24 V weld voltage, minimum corrosion rate is seen, and hence, may be adopted in practice.

Effects of Sm on microstructure and corrosion resistance of hot-extruded AZ61 magnesium alloys

Abstract

Optimization of Operating Conditions Affecting Microbiologically Influenced Corrosion of Mild Steel Exposed to Crude Oil Environments Using Response Surface Methodology

In this study, the influence of four operating parameters (pH, salinity, nitrate concentration and immersion time) and their interactions on the microbiologically influenced corrosion (MIC) rate of mild steel in simulated crude oil environments were investigated by response surface methodology (RSM). 4-level historical data design: pH (A) at 4, 6, 8, 10, salinity (B) at 25, 50, 75 and 100 g/l, nitrate (C) at 25, 50, 75 and 100 g/l and immersion time (D) at 168, 336, 504 and 672 h, was employed to correlate the factors with the corrosion rate as response. A polynomial regression model was developed and validated prior to optimization studies. The result showed that pH has the most influential effect on the response and that the predicted data had a reasonable agreement Original Research Article Salam et al.; BBJ, 7(2): 68-78, 2015; Article no.BBJ.2015.047 69 with the experimental data with the values of R = 0.9660 and Adj-R = 0.9516. The optimum conditions of the crude oil environments were observed at: pH (9.37), salinity (94.73 g/l), nitrate concentration (37.97 g/l) and immersion time of mild steel (168 h) in order to achieve minimum corrosion rate of 0.155196 mpy. The study has revealed that the historical data RSM design is an efficient statistical technique for predicting the optimum operating conditions of crude oil environments required to minimize mild steel corrosion in oil pipelines by incorporating all factors under consideration.

The electrochemical characteristics of commercial aluminium alloy electrodes for Al/air batteries

To develop new materials for Al/air batteries, the evaluation and characterisation of commercial aluminium alloys, namely, Al2000, Al2000Clad and Al7000, as anodes in alkaline electrolyte batteries has been performed. Their self-corrosion rate, hydrogen evolution rate and electrochemical properties, including open circuit potentials, polarisation characteristics and potentiodynamic measurements, were examined in a 4 M KOH solution. Among the tested alloys, Al2000 was found to be the most promising because it exhibits a high open circuit potential, a good anode efficiency and a minimum corrosion rate. Al2000/NiOOH and Al2000/air batteries were tested. Electrolyte concentrations between 0.01 and 4 M KOH were studied, and discharge currents between 0.8 and 20 mA cm−2 were imposed to analyse the evolution of the Ecell. Conversely, the Al7000 alloy exhibited the highest corrosion rate and H2 evolution compared to the other alloys.

Salt Spray Corrosion Performance Associated with the Glass Forming Ability of the FeCo-Based Bulk Metallic Glasses

For the bulk amorphous Fe24+xCo24-xCr15Mo14C15B6Y2(X=0, 2, 4, 6 and 17) alloy, the corresponding corrosion properties associated with glass forming ability (GFA) have been carried out. Neutral salt spray corrosion test results show that the Fe28Co20Cr15Mo14C15B6Y2 alloy has the minimum corrosion rate, followed by Fe26Co22Cr15Mo14C15B6Y2, Fe24Co24Cr15Mo14C15B6Y2, Fe30Co18Cr15Mo14C15B6Y2, Fe41Co7Cr15Mo14C15B6Y2 and Ti6Al4V alloys. Specifically, the Fe28Co20Cr15Mo14C15B6Y2 alloy with the highest GFA also has the best corrosion resistance. With the increasing of Co addition, the corrosion resistance of the FeCo-based bulk metallic glasses is first increases and then decreases, which has the same trend of GFA with the change of Co elements. Furthermore, corrosion morphology are different for FeCo-based BMGs with different Co content.

STUDIES ON MECHANICAL, WEAR AND CORROSION PROPERTIES OF AL6061-BERYL-CERIUM OXIDE HYBRID METAL MATRIX COMPOSITES

The present work mainly investigates the wear behavior and corrosion resistance properties of Al6061/Beryl/Ceo2 hybrid metal matrix composites.Al6061/Beryl/Ce02 hybrid MMCs containing four different wt% (6, 8, 10, 12%) of beryl and keeping 0.2 wt% of cerium oxide constant have been fabricated by using a liquid metallurgy (stir casting) method. The tensile test and hardness test was done according to ASTM standards and a dry sliding wear tests were performed using a Pin-on disc wear testing machine on both composites and a matrix alloys over a load range of 4.905N-19.62N, sliding velocity of 1.66m/s and for various sliding distance of 1-6km, finally corrosion test was done by dipping a sample in 1Molar HCL solution for a duration of 96hrs with increments of 24hrs. The hybrid metal matrix composites was characterized by scanning electron microscopy (SEM) to verify the uniform distribution of Beryl/Ceo2 particles in Al 6061. Further it was observed from the experimental results that the specific wear rate and the corrosion of the composite decreases with the increase in Beryl/Ceo2 particles. The best results of minimum wear rate and minimum corrosion rate was obtained at 12% weight fraction of Beryl and 02% weight fraction of Ceo2.

Optimization of Chemical Environment Condition towards Corrosion Rate of Sulfuric Acid Resistant Alloy Metal (Saramet) Using Response Surface Methodology

This study investigates the variation of sulphuric acid concentration, temperature, and time towards the corrosion rate of saramet using response surfacemethod. Method used in this study is true experimental research. Sarametis material which is included into type of austenitic stainless steel which contains high amount of silicon. Starting at these past 2 years, the material has been widely used.This research used weight loss method. It has been found that minimum corrosion rate is achieved at concentration combination of 89.49% in 3.682 hoursandat temperature of 106,8 °C. From the variation combination, it is seen that the low concentration will decrease ion mobility corrossive ion from saramet.The long period of exposure supports the forming of passive layer which prevent the corrosive ions gets into the steel surface. As a result, corrosion rate decreases. At high temperature, steel which has high silicon content will be stable in terms of its atomic bound which therefore makes it posses high corrosion resistance.

Influence of Paint on Steel Corrosion for Marine Applications

The majority of naval ships are constructed of mild steel. Corrosion is a major concern in a maritime environment. This particular type of material degradation has recently received more attention by the marine industry. The present work aims to investigate the effect of recent coatings used in marine ship surfaces for preventing corrosion. Experiments were performed according to standard tests to evaluate and measure the coating adhesion to steel and to measure the corrosion wear rate if any for three types of coatings. An accelerated corrosion test was conducted to duplicate in the laboratory the field corrosion performance of a product. The results indicate that all tested types of paint have resulted in a reduction in the corrosion rate compared with the uncoated steel. A minimum corrosion rate of 0.8 mm/year for the coat “Hempadur 52,140” was obtained compared to 2.1 mm/year for the uncoated steel. A microscopic examination of the corroded steel surfaces was conducted which prevailed pitting behavior with different degree. The minimum corroded surface exhibited few pitting attack in comparison to other specimens. Although the pitting attack of the surface layer (paint), one can drive a conclusion that sample surface without coating is aggressively attacked by pits.

Corrosion behavior about tubing steel in environment with high H2S and CO2 content

The corrosion behavior of C100 steel in simulated environments with high H2S and CO2 content was studied through high-temperature and high-pressure autoclave, and the H2S stress corrosion cracking (SSC) resistance of C100 steel was evaluated by SSC tests. Scanning electron microscopy (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD) technique were employed to characterize the corrosion products and the metal matrix. The results indicate that all of the corrosion products in this investigation are mainly composed of different types of iron sulfide such as Fe0.95S, FeS0.9, Fe0.985S, Fe7S8 and FeS, and the absence of iron carbonate in the corrosion scales suggests that the corrosion process is governed by H2S corrosion. The corrosion rate decreases in the initial stage and then increases with the enhancement of the temperature. There exists a minimum corrosion rate at about 110 °C. Under the partial pressure of H2S lower than 9 MPa, the corrosion rate decreases with the increase of \(P_{H_2 S} \) While over 9 MPa, a higher \(P_{H_2 S} \) will result in a faster corrosion process. When the applied stress is 72%, 80% and 85% of actual yield strength (AYS), all tested specimens show no crack, which reveals a superior SSC resistance.

A study of flow accelerated corrosion at elbow of carbon steel pipeline by array electrode and computational fluid dynamics simulation

A novel method by combining array electrode technique with computational fluid dynamics (CFD) simulation was proposed to determine the correlation between the corrosion behavior at the elbow of pipeline and the hydrodynamics of fluid flow. It is demonstrated that the distribution of the measured corrosion rates is in good accordance with the distributions of flow velocity and shear stress at the elbow. The corrosion rates at the inner wall of elbow are higher than those at the outer wall of elbow. The maximum corrosion rate appears at innermost side while the minimum corrosion rate at outermost side of the elbow.

Effect of Si-addition as a grain refiner on microstructure and properties of Ti-6Al-4V Alloy

Two different Ti alloys were cast in a graphite mould using vacuum induction skull melting furnace. The first alloy was Ti-6Al-4V and the second was Ti-6Al-4V-0.5Si. Silicon as a grain refiner was added into Ti-6Al-4V alloy, and the effects of Si-addition on the microstructure and properties of the as-cast and swaged alloys were investigated. Hot swaging at 900 °C was performed on the cast samples and then two different thermal treatments were applied. The first treatment was done by heating the swaged samples at 1050 °C to produce fine lamella structure, while the second treatment was carried out at 1050 °C and then decreased the temperature to 800 °C for getting coarse lamella structure. An addition of 0.5% Si to Ti-6Al-4V alloy decreased the grain size of the as-cast sample from 627 to 337 μm. There was an increase in ultimate tensile strength of about 25 MPa for the as-cast Ti-6Al-4V-0.5Si alloy compared to Ti-6Al-4V due to the refinement effect caused by Si addition. A maximum ultimate tensile strength of 1380 MPa and a minimum corrosion rate (1.35×10−6 mm/a in Hank's solution and 5.78×10−4 mm/a in NaCl solution) were reported for the heat treated fine lamella structure of Ti-6Al-4V-0.5Si alloy. The wear rate was decreased to about 50% by adding 0.5% Si at low sliding speeds and to about 73% at high sliding speeds.