Linear Polarization Resistance Measurements Research Articles

“A study on the effect of Co, Cr and Ti on the corrosion of FE40AL intermetallic in molten NaCl–KCl mixture”

The effect of the addition of 3 at% Cr, Co or Ti on the corrosion behavior of Fe40Al intermetallic alloy in 1 M NaCl:1 M KCl mixture at 750 °C has been carried out by using electrochemical techniques. Techniques included potentiodynamic polarization curves, linear polarization resistance and electrochemical impedance spectroscopy measurements. It has been found that the addition of either Cr, Co or Ti decreased the corrosion rate of Fe40Al intermetallic by almost five times due to the formation of a passive layer, absent in the base alloy. This was because the diffusion of Al towards the top of the alloy for the establishment of a protective Al2O3 layer was enhanced by the presence of these alloying elements. The corrosion rate for the base alloy was under diffusion control of the reactants, whereas that for alloyed intermetallic was under charge transfer control.

Hand verification for flexural strength of existing R.C. floors subject to degradation phenomena

In the present paper, a simplified model for hand verification of the flexural and shear strength of existing corroded T beams cast in place of lightened R.C. orthotropic slabs forming floors is presented and discussed. Diffused and pitting corrosion on steel bars, compressive concrete strength degradation and concrete bond strength degradation are included in the model. The original contribution of the paper is evaluation of the flexural and shear strength considering both the cases of strain compatibility and absence of compatibility and considering the main parameters governing the corrosion process. An arch-resistant model for the calculus of the flexural and shear strength of the beam was adopted in the absence of strain compatibility, while the plane section theory was adopted for the case of strain compatibility. No punching shear is considered. This approach is simple and can be applied on the basis of the experimental information available (carbonation test, chloride content, measurement of the pitting in the bar, gravimetric method for general corrosion) or by utilizing analytical expressions calibrated on the knowledge of the corrosion current intensity determined by linear polarization resistance measurement (LPR). The model was also verified against experimental results recently obtained by the authors.

A new method to improve the corrosion resistance of titanium for hydrometallurgical applications

The main objective of the present work was to develop a method to fabricate titanium oxide films with high corrosion resistance by controlled chemical oxidation with H2O2 solutions at 90°C. The prepared chemically oxidized films (COFs) were characterized by X-ray diffraction (XRD) measurements and found to be a mixture of anatase and rutile or pure rutile, depending mainly on the presence of Cl− and SO42− in H2O2 solutions. XRD results indicated that the addition of SO42− ions promoted the formation of anatase; while the addition of Cl− ions favored the formation of rutile. Linear polarization resistance and electrochemical impedance spectroscopy measurements were used to evaluate the corrosion resistance of the as grown COFs for hydrometallurgical applications. Results verified that chemical oxidation with H2O2 solutions is capable of improving the corrosion resistance of Ti for hydrometallurgical applications. Chemical oxidation with 2M H2O2/0.1M HCl solution led to the best improvement of the corrosion resistance of Ti.

Corrosion Behaviour of TiC-Reinforced Hadfield Manganese Austenitic Steel Matrix In-Situ Composites

The corrosion behaviour of Hadfield manganese austenitic steel matrix composite reinforced with the varying amount of TiC and unreinforced Hadfield manganese austenitic steel matrix alloy has been evaluated in 3.5% NaCl aqueous solution with the pH value of 6 by the potentiodynamic polarization curves and linear polarization resistance measurements at a scan rate of 1 mV/s at room temperature (25°C ± 2°C). The corrosion rate of the composites is higher than that of their unreinforced matrix alloy and it increases with the increasing volume fraction of TiC. The poor corrosion resistance of the composites can be attributed to the galvanic effects between the matrix and reinforcement.

A Lifetime of Metallic Nanoparticles in Heat Exchange Liquids

This work is focused on lifetime prediction of metallic nanoparticles in heat exchange nanofluids. Copper, nickel and iron nanoparticles were studied in 40 wt.% aqueous solution of potassium formate and propylene glycol. Materials were observed by means of mass loss exposure tests, linear polarization resistance and potentiodynamic measurements. Potassium formate solution is not suitable bearing liquid for metallic nanoparticles. Propylyne glycol seems promising, however additional corrosion prevention needs to be applied.

Galvanic corrosion of electric resistance welded X52 steel in CO2-containing solution

Purpose – This paper aims to report an experimental investigation of the galvanic corrosion that occurs between the base metal and the welds in X52 carbon steel petroleum pipelines when exposed in carbon dioxide (CO2)-containing saltwater at pH 4 at room temperature. The pipeline was fabricated by electric resistance welding (ERW). Design/methodology/approach – The experimental setup was a closed glass cell equipped with a silver/silver chloride (Ag/AgCl) reference electrode, two working electrodes (the weld metal and the parent steel specimens) and a gas bubbler. The corrosion potential and polarization resistance of the base metal and the weld were determined using electrochemical testing methods: potentiodynamic polarization scans and linear polarization resistance measurement. The galvanic currents of the base metal when coupled to the weld metal were measured using zero resistance ammetry. Findings – The weld metal was the anode of the couple for a very short time at the beginning of the experiment and then became the cathode until the end of the experiment. This indicates that electric resistance welded X52 steel pipe is a promising material to be operated in CO2-containing saltwater at pH 4 and 25°C because the weld area is cathodic to the parent metal, the value of the galvanic current is very low (in the order of nanoamps) and the area of the anode (i.e. the parent metal) is significantly larger than that of the cathode (weld metal). Research limitations/implications – Further experimental research could be performed to investigate the galvanic corrosion behavior between the parent metal and the weld area of X52 carbon steel petroleum pipelines in CO2-containing saltwater at different pH values, temperature and velocity. Practical implications – Electric resistance welded X52 steel pipe is a promising material for use with CO2-containing saltwater environments at pH 4 and 25°C. Originality/value – The new information presented in the paper is the galvanic corrosion behavior between the parent metal and the ERW weld metal of X52 carbon steel in CO2-containing solutions. The paper should be useful to researchers working in the field of oil industry corrosion.

Stress Corrosion Cracking of API 5lX52 in Ethanolic Environment

The human interest on renewable energy it is due environmental preservation. In substitution of Methyl-therbutyl-ether (MTBE), ethanol it is being used as replacement of the oxidant agent in gasoline, because not only increases the fuel octane number and represents the best option for the increasing demand for fossil fuel observed over the last few years. However, one of the most common failures on mild steel found in ethanolic environments is stress corrosion cracking (SCC) and pitting corrosion. Based on the report of American Petroleum Institute (API), the safer way for transporting the blend is by the existing pipeline.Thus, the aim of the present study is to investigate the effect of water content (0.5%, 5%, 10% ) in E95 blends on the stress corrosion cracking susceptibility of API 5L X-52 steel. In order to assess the steel mechanical and electrochemical response, slow strain rate tests (SSRT) of 1 X 10-6 s-1, coupled with electrochemical noise measurements (ECN) were carried out. In addition, the material response immersed into the various solutions was analyzed by using linear polarization resistance (LPR) measurements and weight loss measurements. Furthermore, fracture surface observations by scanning electron microscopy (SEM) on samples exposed to the various solutions were done. In general, a ductile behavior was observed. However, secondary cracking was only observed for specimens exposed to solution containing up to 2%V water. ECN gave indication of a likely localized corrosion process occurring at low water concentrations, whereas for water content above 2%V, a uniform corrosion process seems more likely to occur. the LPR results indicated that specimens exposed to water content up to 2%V disclosed the lower corrosion rates. Further, the results of weight loss measurements supported the behavior found.

An Electrochemical Study of H2O2 Oxidation and Decomposition on Simulated Nuclear Fuel (SIMFUEL)

The anodic oxidation and open circuit decomposition of H2O2 on UO2+x surfaces have been investigated voltammetrically and using linear polarization resistance measurements over the pH range 9.5 to 12.6. At the lower pH values both the anodic oxidation and decomposition reactions are almost completely blocked by a thin surface layer of UVI oxide. At higher pH this layer becomes more soluble and anodic oxidation occurs on the sublayer of UIV1–2xUV2xO2+x, but is partially controlled by transport through a permeable, chemically dissolving UVI oxide/hydroxide layer. At positive electrode potentials (0.3V vs. saturated calomel electrode), approximately 70% of the anodic current is consumed by H2O2 oxidation the remaining 30% going to produce UVIO2(OH)x(2−x)+. At higher pH values, H2O2 decomposition occurs on an unblocked UIV1–2xUV2xO2+x surface and the pH dependence of the reaction suggests HO2− is the electroactive form of peroxide

Influence of Molecular Weight on Mild Steel Corrosion Inhibition Effect by Polyvinyl Alcohol in Hydrochloric Acid Solution

The corrosion inhibition of mild steel in hydrochloric acid solution in the presence of three different molecular weights of polyvinyl alcohol (PVA) designated as PVA-I, PVA-II, and PVA-III corresponding to 14,000, 72,000, and 125,000 g mol−1, respectively, was investigated using electrochemical impedance spectroscopy, linear polarization resistance (LPR), and potentiodynamic polarization techniques at 25°C. It was found that PVA of different molecular weights inhibited the corrosion of mild steel in the acid environment. Inhibition efficiency (η%) increases with increase in concentration of the polymers. LPR measurements clearly show that inhibition efficiency increases with increasing molecular weight in the order PVA-III > PVA-II > PVA-I. Polarization curves indicate that PVA functions as a mixed inhibitor affecting both the anodic metal dissolution and cathodic hydrogen evolution partial reactions of the corrosion process. The experimental data obtained fitted well into Langmuir adsorption isotherm model. Physical adsorption mechanism is proposed from the thermodynamic (free energy of adsorption) parameters obtained.

Effect of inhibitors on preferential weld corrosion under sweet conditions

Purpose – The aim of this investigation was to compare the performance of three typical oil field carbon dioxide corrosion inhibitors in controlling preferential weld corrosion (PWC) of X65 pipeline steel in artificial seawater (3.5 weight per cent) saturated with carbon dioxide at one bar pressure. Design/methodology/approach – A novel rotating cylinder electrode (RCE) apparatus was used to evaluate the effect of flow on the inhibition for the weld metal (WM), heat-affected zone (HAZ) and parent material. To fulfill this objective, the galvanic currents flowing between the weld regions were recorded using parallel zero-resistance ammeters, and the self-corrosion rates of the couples were obtained by linear polarization resistance measurements. Findings – The results showed that when 30 ppm of green oil field inhibitors were present in the service environment, a current reversal took place, resulting in accelerated weld corrosion. At high shear stress, the currents increased and further reversals occurred. The inhibitors were more effective in controlling the self-corrosion rates of the parent material than of the WM and HAZ material. It was concluded that PWC was caused by unstable conditions in which the inhibitor film was selectively disrupted from the WM and HAZ, but remained effective on the parent material. Originality/value – Electrochemical corrosion rate measurements were carried out using an RCE produced from the different regions of the weld. An advantage of using the RCE is that the hydrodynamic conditions are very well defined, and it is feasible to translate the conditions that are known to exist in a production pipeline to those used in laboratory tests.

Evaluation of corrosion inhibition of mild steel in 0.1 M HCl by 4-amino-3-hydroxynaphthalene-1-sulphonic acid

The corrosion behaviour of 4-amino-3-hydroxynaphthalene-1-sulphonic acid (4A3H1S) in 0.1M HCl on mild steel (MS) was measured by electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and potentiodynamic measurements at various concentrations. The surface morphology of the MS was examined by scanning electron microscopy (SEM) both in the absence of an inhibitor and in the presence of a 10mM 4A3H1S-containing corrosive medium. The inhibition mechanism was determined by the potential of the zero charge (Epzc) measurement at the solution–metal interface. The adsorption of 4A3H1S on the surface of MS obeyed the isotherm of Langmuir adsorption.

Electrochemical study on effect of Au, Ag, Pd and Pt on corrosion behaviour of Fe3Al in molten NaCl–KCl

The corrosion behaviour of Fe3Al intermetallic alloyed with 1 at-%Ag, Au, Pt and Pd in NaCl–KCl (1∶1M) at 700°C, typical of waste gasification environments, has been evaluated using polarisation curves, linear polarisation resistance and electrochemical impedance spectroscopy measurements and compared with an Ni based alloy, namely Inconel 600. Results have shown that, for short testing times, the addition of noble elements increased the corrosion rate for base Fe3Al intermetallic alloy, but it was decreased for long testing times by forming a protective corrosion product layer. Additionally, base Fe3Al intermetallic alloy had higher corrosion rates than Inconel 600.

Experimental studies of 2-pyridinecarbonitrile as corrosion inhibitor for mild steel in hydrochloric acid solution

The effect of 2-Pyridinecarbonitrile (2-PCN) was studied on mild steel (MS) corrosion in 0.1molL−1 HCl by electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and potentiodynamic polarization measurements. The surface morphologies of the MS were investigated in the inhibitor-free and in the presence of 10mmolL−1 2-PCN containing corrosive media, at 120h exposure period by scanning electron microscopy (SEM). The mechanism of adsorption was determined from the potential of zero charge (Epzc). 2-PCN adsorption on the MS surface obeyed the isotherm of Langmuir and the thermodynamic parameters Kads; ΔGads° were also calculated and discussed.

Electrochemical Study of Ni20Cr Coatings Applied by HVOF Process in ZnCl2-KCl at High Temperatures.

Corrosion behavior of Ni20Cr coatings deposited by HVOF (high velocity oxygen-fuel) process was evaluated in ZnCl2-KCl (1 : 1 mole ratio) molten salts. Electrochemical techniques employed were potentiodynamic polarization curves, open circuit potential, and linear polarization resistance (LPR) measurements. Experimental conditions included static air and temperatures of 350, 400, and 450°C. 304-type SS was evaluated in the same conditions as the Ni20Cr coatings and it was used as a reference material to assess the coatings corrosion resistance. Coatings were evaluated as-deposited and with a grinded surface finished condition. Results showed that Ni20Cr coatings have a better corrosion performance than 304-type SS. Analysis showed that Ni content of the coatings improved its corrosion resistance, and the low corrosion resistance of 304 stainless steel was attributed to the low stability of Fe and Cr and their oxides in the corrosive media used.

Evaluation of the corrosion behavior of the polyester-coated galvanized steel subjected to SO2 gas under different relative humidities

Evaluation of the corrosion behaviour of the polyester-coated galvanized steels exposed to different relative humidities was utilized using electrochemical impedance spectroscopy (EIS), anodic polarization curves and linear polarization resistance (LPR) measurement techniques. The samples were exposed to SO2 gas in laboratory conditions that was adjusted to various relative humidities. The results obtained from current-potential curves indicate that, corrosion current density of polyester-coated samples increases as the relative humidity increases in SO2 containing medium. The EIS results showed that polyester-coated samples exposed to relative humidity (RH) of 70% experienced defect-free coating, whereas the samples significantly lost their protection behaviour under relative humidities of 80, 90 and 100%.

Corrosion Study of Super Ferritic Stainless Steel UNS S44660 (26Cr-3Ni-3Mo) and Several Other Stainless Steel Grades (UNS S31603, S32101, and S32205) in Caustic Solution Containing Sodium Sulfide

Electrochemical techniques, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were used in this study to show how the corrosion mechanism of several commercial grades of stainless steel in hot caustic solution is strongly influenced by the presence of sodium sulfide. Experimental results from super ferritic stainless steel UNS S44660 (26Cr-3Ni-3Mo) were compared to austenitic stainless steel UNS S31603, lean duplex stainless steel (DSS) UNS S32101, and standard DSS UNS S32205 in caustic solution, with and without sodium sulfide, at 443 K (170 °C). Weight loss measurements indicated that corrosion rates of UNS44660 were much lower than the other grades of stainless steel in the presence of the sodium sulfide. Potentiodynamic polarization and linear polarization resistance measurements showed that the electrochemical behavior was altered by the adhesion of sulfur species, which reduced the polarization resistances and increased the anodic current densities. SEM and XPS results imply that the surface films that formed in caustic solution containing sodium sulfide were defective due to the adsorption of sulfide, which destabilized the passive film and led to the formation of insoluble metal sulfide compounds.

Assessment of Preferential Weld Corrosion of Carbon Steel Pipework in CO2-Saturated Flow-Induced Corrosion Environments

Preferential weld corrosion (PWC) has posed a problem to the oil and gas industry for a number of years. The general consensus from authors is that environmental effects take precedence over the weld chemical composition and microstructure. Therefore, the primary approach is to ensure the correct corrosion inhibitor selection and application to prevent PWC. Although there has been considerable focus directed toward the effect of flow rate on PWC in inhibited carbon dioxide (CO2)-saturated environments, the consideration of a higher, localized turbulence over the weld material and the implications this has on PWC appears minimal. This paper considers this effect by reviewing the performance of a commercially available, film-forming oilfield corrosion inhibitor using a submerged impinging jet (SIJ). The dual nozzle arrangement of the SIJ allowed a carbon steel parent metal and a 1% Ni, 0.25% Mo weld material to be subjected to the same brine chemistry, but different flow conditions. The velocity over the parent metal was kept constant at 7 m/s while the weld material was subjected to velocities of 7, 8.8, and 11.4 m/s to simulate different severities of turbulence. Galvanic current and linear polarization resistance (LPR) measurements were used to assess the weld resistance to PWC. Although the weld was shown to be cathodic to the parent metal, increasing velocity and turbulence at the weld relative to the parent metal was found to reduce the galvanic current, suggesting increased susceptibility of the weld to corrosion. The addition of inhibitor at 100 ppm accentuated this effect and led to a reversal of the galvanic current when the relative velocities were 7 m/s and 11.4 m/s for the parent metal and weld, respectively. The paper discusses the power of this galvanic technique for prediction of the conditions conducive to accentuating PWC.

Materials and Corrosion 4/2013

Materials and CorrosionVolume 64, Issue 4 Cover PictureFree Access Materials and Corrosion 4/2013 First published: 12 April 2013 https://doi.org/10.1002/maco.201390012AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Cover: Sol-gel films of tetraethoxysilane (TEOS), phenyltriethoxysilane (PTES) and phenyltrimethoxysilane (PTMS) were prepared on aluminium and aluminium alloy AA7075 and characterized. The corrosion inhibition properties of uncoated and coated specimens were evaluated with potentiodynamic polarization scan, linear polarisation resistance and open circuit potential measurements. With scanning electron microscopy and optical microscopy effects of the sol-gel coating were shown. Weight loss measurements were performed at different pH-values. More hydrophobic coatings as PTMS show a considerably better corrosion inhibition capacity as compared to the capacity provided by less hydrophobic ones as TEOS and PTES. The pictures show samples of the alloy AA 7075 uncoated (top) and coated with PTMS (bottom) before (left) and after (right) immersion for aqueous solution of 0.05 mol/l NaCl for 24 days with obvious corrosion damage. The inset shows potentiodynamic curves for all alloy samples after immersion in an aqueous solution of 0.05 mol/l NaCl for 24 hr. Results obtained with all employed methods correlate well with the hydrophobicity of the coating with an efficiency growing according to PTMS < PTES < TEOS as visible at the corrosion potentials in the diagram. More detailed information can be found in: A. A. Younis, W. Ensinger, M. M. B. El-Sabbah, R. Holze; Corrosion protection of pure aluminium and aluminium alloy (AA7075) in salt solution with silane-based sol-gel coatings; Materials and Corrosion 2013, 64, 276. Volume64, Issue4April 2013 RelatedInformation

Fretting corrosion of fully cemented polished collarless tapered stems: The influence of PMMA bone cement

In order to investigate the effect PMMA bone cement chemistry has on the fretting corrosion of cemented femoral stems, a novel test setup with integrated electrochemistry was developed and conducted in part reference to ISO 7206-4:2010. Ultima TPS™ femoral stems were cemented into a specially prepared delrin moulds using a third generation cementing technique similar to the procedure used in-vivo. Three commercially available PMMA bone cements were tested in order to understand the role bone cement chemistry plays on the fretting-corrosion rates at the stem-cement interface. Each stem-cement component was then orientated and set in place using laboratory grade PMMA cement, immersed in 0.9% NaCl and subjected to 500,000 cycles of cyclic loading at 1Hz. Intermittent Open Circuit Potential (OCP) and Linear Polarisation Resistance (LPR) measurements were conducted in order to assess the effect PMMA bone cement chemistry has on the localised dissolution of cemented femoral stems. Macroscopic observation and scanning electron microscopy with integrated energy dispersive X-ray analysis (SEM/EDX) was conducted in order to support the electrochemical findings.

Electrochemical behavior of steel/acid interface: adsorption and inhibition effect of oligomeric aniline

The present work shows the development of new protective oligomeric aniline (O-ANI) and its effect on electrochemical corrosion behavior of low carbon steel (LCS) in 1 M HCl at 308 K. The synthesized O-ANI was subjected to spectroscopic and electrochemical characterizations. The inhibition of LCS corrosion by O-ANI was studied using open circuit potential (OCP), potentiodynamic polarization (PDP), linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) measurements. The potentiodynamic polarization data indicated that O-ANI suppresses predominantly the cathodic process of corrosion reaction in comparison to the anodic process. The inhibition efficiency of the O-ANI depends on the length of the oligomeric chain and position of the functional groups. The spectra of all elements, within limits, on the steel surface was determined by energy-dispersive X-ray spectroscopy (EDX). Morphological changes on the electrode surface were monitored by scanning electron microscopy (SEM). The thermodynamic parameters such as the adsorption equilibrium constant (Kads) and the free energy of adsorption (ΔG°ads) were calculated and discussed. Several adsorption isotherms were tested and the experimental data fitted well with the Langmuir adsorption isotherm. UV-visible spectral analysis of O-ANI solution containing LCS indicates the formation of Fe–N (ligand–metal) charge-transfer complex type interaction.