Linear Polarization Techniques Research Articles

Effect of Pre-Ageing Thermal Conditions on the Corrosion Properties of Antimony-Modified Al-Si-Mg Alloy

The purpose of this investigation was to evaluate the effect of pre-ageing thermal conditions on the corrosion properties of antimony-modified Al-Si-Mg alloy.The alloy was subjected to a Single Thermal Ageing Treatment; STAT (T6 temper-solution heat treatment and ageing) and Double thermal ageing treatment; DTAT (T7 temper- solution heat treatment and ageing for stabilization). These consist of solution heat treatment (SHT) at 540 o C for 1hr, water quenched followed by an artificial ageing; DTAT and STAT. For the single thermal ageing treatment (STAT), quenched samples were aged at temperatures of 180 0 C for 2hrs, before cooling in air. In the double thermal ageing treatment (DTAT), quenched samples were pre-aged at a temperature of 90 o C, 105 o C and 120 o C for 1- 5 hrs. This was followed by ageing at 180 o C for 2hrs before cooling in air. The corrosion characteristic of the as-cast, Single Thermal Ageing Treatment (STAT) and Double Thermal Ageing Treatment (DTAT) were evaluated using weight loss and linear polarization techniques in a static 3.5%NaCl solution. From the results, the corrosion rate decreases with increasing pre-ageing time and temperatures. Equally, from the linear polarization data/curves, the corrosion rate of the treated alloy decreases at all ageing temperatures along with the ageing time. The Optical Microscope (OM) results of as-corroded samples revealed that the alloy suffers pitting/uniform corrosion. The corrosion behaviour of the DTAT samples in simulated seawater showed an excellent improvement in corrosion resistance than the as-cast and conventional STAT alloy. http://dx.doi.org/10.4314/njt.v34i4.6

Effect of some peel extracts on the corrosion behavior of aluminum alloy in alkaline medium

The inhibition performance of three peels, for instance Pisum sativum (PS), Solanum tuberosum (ST), and Citrus reticulata (CR), on aluminum alloy (AA) in 1 M NaOH solution was investigated using weight loss, electrochemical impedance spectroscopy (EIS), linear polarization, and potentiodynamic polarization techniques (Tafel). It was found that these three peel extracts exhibit very good performance on AA in alkaline medium. PS exhibited maximum inhibition efficiency (η%) of 94.5 % at 1.5 g/L. The effective protection of AA in inhibited system was investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The adsorption of inhibitors on AA surface obeyed the Langmuir’s adsorption isotherm. Potentiodynamic polarization studies showed mixed mode of corrosion inhibition for all the inhibitors. SEM and AFM complemented well with those obtained from weight loss and electrochemical studies.

Electrochemical investigation of the epoxy nanocomposites containing MnAl2O4 and CoAl2O4 nanopigments applied on the aluminum alloy 1050

The MnAl2O4 and CoAl2O4 nanopigments were synthesized through solution combustion method. The nanopigments extracts in the 3.5 wt% NaCl solution were prepared. Electrochemical impedance spectroscopy (EIS) and linear polarization (LP) techniques were utilized to investigate the corrosion inhibition properties of the pigments in the solutions containing pigments extracts. The epoxy nanocomposites were prepared and applied on the aluminum specimens. EIS and pull-off measurements were performed to characterize the corrosion protection properties of the epoxy nanocomposites. It was revealed that the MnAl2O4 pigment showed higher corrosion inhibition properties than CoAl2O4 in the solution phase. In addition, MnAl2O4 enhanced the corrosion resistance and decreased the adhesion loss of the epoxy coating on the aluminum substrate significantly. The MnAl2O4 nanopigment improved the corrosion resistance of the epoxy coating through increasing the barrier performance and releasing inhibitive species.

Synergy between Galvanic Protection and Self-Healing Paints.

Painting is a cost-effective technique to delay the onset of corrosion in metals. However, the protection is only temporary, as corrosion begins once the coating becomes scratched. Thus, an increasingly common practice is to add microencapsulated chemical agents to paint in order to confer self-healing capabilities. The additive's ability to protect the exposed surface from corrosion depends upon (i) how long the chemical agent takes to spread across the exposed metal; (ii) how long the agent takes to form an effective barrier layer; and (iii) what happens to the metal surface before the first two steps are complete. To understand this process, we first synthesized 23 ± 10 μm polyurea microcapsules filled with octadecyltrimethoxysilane (OTS), a liquid self-healing agent, and added them to a primer rich in zinc, a cathodic protection agent. In response to coating damage, the microcapsules release OTS into the scratch and initiate the self-healing process. By combining electrochemical impedance spectroscopy, chronoamperometry, and linear polarization techniques, we monitored the progress of self-healing. The results demonstrate how on-demand chemical passivation works synergistically with the cathodic protection: zinc preserves the surface long enough for self-healing by OTS to reach completion, and OTS prolongs the lifetime of cathodic protection.

Interfacial investigation and strengthening behaviour of Zn–Ni multifacial TEA/MEA thin films induced by electrodeposition

Zinc–nickel films were obtained by electrocodeposition using electrolytic deposition techniques in the presence of TEOA (C6H15NO3) and a surfactants consisting of triethylamine and monoethylamine with other bath additives. The modified structure of the films was analysed with scanning electron microscopy attached to energy-dispersive spectrometer, atomic force microscope and X-ray diffraction. Micro-hardness and corrosion of the coated body was examined and used as a criterion to justify the adhesion of the crystal deposited. The corrosion resistance of the coated and uncoated composites was studied in 3.5 % sodium chloride static solution using linear polarization technique. The hardness value increased from 38HV—substrate to 180HV—coated body, indicating a 78.89 % improvement. Equally, the corrosion resistance of the deposited matrix was enhanced by 84.62 %.

Influence of Mo content on the phase evolution and corrosion behavior of model Fe–9Cr–xMo (x = 5, 7, and 9 wt%) alloys

Abstract

Effect of polyaniline salts on the mechanical and corrosion properties of organic protective coatings

Abstract The aim of this work was to assess the effect of polyaniline salts (PANI-HA) with various dopant types on the mechanical and corrosion properties of organic protective coatings dependent on the pigment volume concentration. The doping acids used included phosphoric acid (H 3 PO 4 ), sulphuric acid (H 2 SO 4 ), hydrochloric acid (HCl), p-toluenesulphonic acid (PTSA), and 5-sulphosalicylic acid (CAS). The polyaniline salt types were described by their physico-chemical parameters. An epoxy ester resin was used as the binder for the organic coatings. The organic protective coatings included the various PANI-HA types. The prepared organic coatings were subjected to mechanical testing, corrosion tests and linear polarisation technique. Organic coatings achieved during mechanical tests comparable results regardless of the type of PANI dopant or PVC (pigment volume concentration) with the exception of organic coatings fulfilling the condition PVC = CPVC (critical pigment volume concentration) which exhibited decrease of mechanical resistance. The results of accelerated corrosion tests and techniques of linear polarisation testify that in particular the PVC parameter affects the resulting corrosion resistance. During those tests, the organic coatings exhibited improved corrosion resistance, particularly at low pigment volume concentrations (PVC = 0.1–5%) irrespective of the pigment used.

Corrosion Behavior of Ti and Ti Based Alloys Used as Implants-Supported Mandibular Overdentures

In the present study, four different types of the commercial dental implants used as support for total/partial dental prosthesis have been investigated. Pure Ti and Ti6Al4V alloy, provided by four different manufactures, were chosen because these were the most used in dentistry market. The corrosion resistance was evaluated by using linear polarization technique, after recording the open circuit curves in Fusayama Meyer artificial saliva for 240 minutes. The corrosion tests in artificial saliva with pH 5.2 have shown that pure Ti exhibited a better behavior than the Ti alloy. This result can be explained by a higher stability of the passive thin layer of titanium oxide than the complex oxide layer formed on the Ti alloy surface.

The effect of polypyrrole and nickel + polypyrrole coatings on corrosion behaviour AISI 304 stainless steel

Polypyrrole (PPy) and nickel + PPy (Ni + PPy) coatings have been occured on AISI 304 stainless steel (304 SS) surface by cyclic voltammetry technique in aqueous oxalic acid solutions and as the supporting electrolytes was used saccharin and NaNO3. Corrosion behavior of the PPy and Ni + PPy coated 304 SS electrodes was investigated using linear anodic polarization, Tafel extrapolation and electrochemical impedance spectroscopy (EIS) techniques in various aqueous solutions. The polypyrrole coated samples were characterized by scanning electron microscope (SEM) and Fourier Transform Infrared spectroscopy (FTIR). SEM analysis showed that PPy structure depends closely on the electrochemical conditions. Additionally, it is seen from FTIR analysis, characteristic polypyrrole absorption bands have occurred in all the coated surfaces. Tafel analyses and open-circuit potential datas revealed that the PPy and Ni + PPy coatings effectively protect the steel from corrosion in H2SO4 and NaOH solutions. However, the corrosion protection properties were reduced with immersion time. Ni + PPy coatings more effectively protects the steel from corrosion than polypyrrole

An evaluation of the anticorrosion properties of the spinel nanopigment-filled epoxy composite coatings applied on the steel surface

Abstract MnAl 2 O 4 nanopigment was synthesized through co-precipitation method. The composition and morphology of the pigment were investigated by X-ray diffraction and scanning electron microscope. Electrochemical impedance spectroscopy (EIS) and linear polarization techniques were utilized to investigate the corrosion inhibition performance of the pigment. Scanning electron microscope (equipped by energy dispersive spectroscopy) was utilized in order to evaluate the surface morphology and composition of the steel samples exposed to the solutions without and with nano-MnAl 2 O 4 pigment. Solubility of nano-MnAl 2 O 4 pigment in the 3.5 wt% NaCl solution was evaluated by inductively coupled plasma test method. Results obtained from X-ray diffraction analysis revealed that nano-MnAl 2 O 4 pigment was synthesized successfully. Results obtained from inductively coupled plasma and electrochemical measurements showed that nano-MnAl 2 O 4 pigment could significantly reduce the corrosion rate of the steel sample immersed in the 3.5 wt% NaCl solution through releasing inhibitive species. Epoxy nanocomposite coatings containing 3 wt% Al 2 O 3 and MnAl 2 O 4 nanoparticles were produced. The epoxy nanocomposites were applied on the steel surface and then their corrosion protection properties were evaluated by EIS. Results showed that the MnAl 2 O 4 nanopigment filled coating showed higher corrosion resistance than the coating loaded with Al 2 O 3 nanoparticle.

Investigation on microstructural, anti-corrosion and mechanical properties of doped Zn–Al–SnO2 metal matrix composite coating on mild steel

In this study, the microstructural, mechanical and anti-corrosion properties of nanocomposite Zn–Al coating containing SnO2 nanoparticles prepared from sulphates electrolyte by electrodeposition on mild steel substrate was investigated. The morphologies of the coating were analysed using SEM/EDS, AFM Raman and X-ray diffraction. The anticorrosion behaviour of the coating prepared with different concentrations of SnO2 (7 and 13g/L) and potential of (0.3 and 0.5V) was examined in 3.65% NaCl solution by using linear polarization techniques. The wear and hardness properties of the coatings were performed under accelerated reciprocating dry sliding wear tests and diamond micro-hardness tester respectively. The results obtained showed that the incorporation of SnO2 in the plating bath brings an increase in corrosion resistance and mechanical properties of Zn–Al–SnO2 composite coatings. The SEM images showed a homogeneous grain structure and finer morphology of the coatings. The hardness values was found to improve with the amount of the SnO2 embedded into the Zn–Al metal deposit and effective deposition parameters.

Studying the effects of surface modification of Cr2O3 nanoparticles by 3-aminopropyltrimethoxysilane (APTMS) on its corrosion inhibitive performance

Cr2O3 nanoparticles were modified with 3-aminopropyltrimethoxysilane (APTMS). The APTMS grafting on the surface of the nanoparticles was analyzed by turbidimeter, thermal gravimetric analysis and Fourier transform infrared spectroscopy. The corrosion performance of the mild steel panels immersed in the 3.5 wt% NaCl solutions containing modified and unmodified pigments extracts was studied by electrochemical impedance spectroscopy and linear polarization techniques. The surface morphology of the samples was characterized by scanning electron microscopy. The type and concentration of the released ions from the pigments were measured by inductively coupled plasma. Results revealed that APTMS grafted on the surface of nanoparticles successfully. It was found that Cr2O3 nanoparticles released inhibitive species causing the decrease of corrosion rate of the steel sample in the 3.5 wt% NaCl solution. However, the unmodified nanoparticles released higher ions and showed better inhibitive performance than the modified one. A lower surface degradation of the steel specimen exposed to the solution containing unmodified pigment extract was observed compared to the modified one.

Potential Solutions to Increase the Corrosion Resistance of Metallic Surgical Instruments Using Different Types of Ceramic Coatings

The overwhelming majority of medical instrumentation are executed form metalic materials, form the category of austenitic steinlees steel and titan alloys, which poses a good rezistance to corrosion, appropriate mechanical properties, and a good biocompatibility. The lifetime for the medical instrumentation is generaly low due to the modification of surface properties of metal tools from poor maintenance by medical personnel performing decontamination and sterilization operations (having no knowledge of material science), or the the improper use of chemical reagents or low quality of water used in decontamination processes. Identified solutions to improve surface properties of these parts of surgical instruments made ​​of metallic consist of deposition of protective coatings. In this experimental study, we perform different coatings on a substrate made by stainless steel type 316L. We use different coating materials, each deposited ​​by a specific method: hard ceramic biomaterials (TiO2 and YSZ - yttria stabilized zirconia) deposited by the method of deposition and plasma, respectively zirconium carbonitride (mono and multilayer) deposited by cathodic arc deposition method. The obtained coatings was analyzed using scanning electron microscopy coupled with EDS in order to characterize the morphology and composition of the coatings. The selected samples were tested for corrosion resistance. Corrosion resistance was determined by linear polarization technique, which involves plotting the potentiodynamic polarization curves of-1 V (vs. OC) to 1 V (vs SCE), with a scan rate of 0.5 mV / s. The corrosion tests was performed in physiological saline infusion (NaCl concentration 7%) at room temperature (25 ± 1 ° C) according to ASTM G15-97a. As a general conclusion we can say that layers ZrCN based presents the best parameter values ​​of corrosion and therefore the best corrosion resistance in the case of surgical instruments.

BiOCl micro-assembles consisting of ultrafine nanoplates: A high performance electro-catalyst for air electrode of Al–air batteries

BiOCl micro-assembles appearing spherical and plate-like in shape consisting of ultrafine nanoplates were successfully synthesized by a simple hydrothermal method. The obtained BiOCl micro-assembles were characterized as oxygen reduction reaction (ORR) catalyst for air electrode of aluminum air batteries by using linear polarization and constant-current discharge techniques. The effect of precursor concentration on the electrochemical properties of the air electrodes based on the synthesized BiOCl micro-assembles was intensively investigated. The results demonstrated that the BiOCl catalyst exhibited promising ORR performance. Koutecky–Levich analysis indicated that a two-electron reaction was favored for the ORR mechanism of the BiOCl (0.18) sample.

Corrosion and wear mechanisms of aluminum alloys surface reinforced by multicharged N-implantation

Abstract Samples of Al-1050 and of Al-2024 aluminum alloys were implanted by means of nitrogen multicharged ion beam provided by an ECR source. Wear and corrosion tests were performed in order to qualify and quantify the surface enhancement created by implantation. The tests performed, respectively, using ball-on-disk set up and linear polarization technique, combined with SEM observations and correlated with microstructural study already published, made possible the identification of damaging mechanisms of nitrogen implanted aluminum surface. The study underlines the importance which has to be given to the implanted fluence and to the initial microstructure, if a consistent surface improvement is targeted. It is demonstrated in this work that the improvement of wear resistance is strongly linked to the intrinsic properties of the nitride protective layer and not to the initial microstructure which only affects optimum fluence. Corrosion tests reveal inverse tendency. The alloy composition is, in this case, of importance, contrarily to implanted fluencies which do not affect the results. This study also shows that if nitrogen implantation is good for surface resistance, a pit (corrosion) or a crack (wear) of implanted surface causes more damage than corrosion or wear of untreated surface.

THERMODYNAMIC STUDY AND ELECTROCHEMICAL INVESTIGATION OF CALCEIN AS CORROSION INHIBITOR FOR MILD STEEL IN HYDROCHLORIC ACID SOLUTION

The corrosion behaviour of mild steel in 1.0 M HCl solution containing different concentrations of Calcein at different temperatures was investigated using the impedance, potentiodynamic polarization and linear polarization techniques. Long term tests were accomplished by hydrogen gas evolution and impedance measurements. The results showed that inhibition efficiency has increased with the inhibitor concentration and temperature increment. The adsorption of the inhibitor on the mild steel surface obeyed the Langmuir isotherm. Activation energy values at concentrations of Calcein were lower than that of uninhibited system. The thermodynamic parameters of adsorption deduced reveal a strong interaction of Calcein on the mild steel surface.

The extract of Jamun (Syzygium cumini) seed as green corrosion inhibitor for acid media

The corrosion inhibition of mild steel in hydrochloric acid and sulfuric acid solutions by the extract of Syzygium cumini seed was studied using chemical, electrochemical impedance spectroscopy, linear polarization, and potentiodynamic polarization techniques. The inhibition was assumed to occur via adsorption of the inhibitor molecules on the metal surface. The adsorption of the extract on the mild steel surface obeyed Langmuir’s isotherm. The results obtained showed that the extract of S. cumini could act as an effective inhibitor of the corrosion of mild steel in hydrochloric and sulfuric acid media.

Effect of Avogadro Oil as Corrosion Inhibitor of Thermally Pre-aged Al-Si-Mg Alloy in Sodium Chloride Solution

The corrosion inhibition of thermally pre-aged Aluminium-Silicon-Magnesium (Al-Si-Mg) alloy in 3.5 % NaCl solution with natural Avogadro oil of varying concentrations has been studied using linear polarization techniques. From the results obtained, the corrosion rate decreased with an increase in Avogadro oil concentration. An inhibitor efficiency of 46.7, 58 and 71 % were obtained at 1.5, 3.0, 4.5 g/v Avogadro oil addition in a 3.5 % NaCl solution respectively for the conventional alloy. Results from the linear polarization technique indicate a higher potential value with an increase in the polarization resistance (R p ) and lower current density in the inhibited samples than the uninhibited Al-Si-Mg alloy as obtained from the Tafel plot extrapolation. There exist some levels of correlation in the inhibitor efficiency between the conventional and the thermally pre-aged Al-Si-Mg alloy/Avogadro oil in 3.5 % NaCl solution.

Empirical equation of sulphate reducing bacteria (SRB) corrosion based on abiotic chemistry approach

Purpose – The purpose of this paper is to develop an empirical equation of SRB corrosion based on their metabolic species.Design/methodology/approach – Solution containing SRB metabolic species was simulated using abiotic chemistry approach. Linear polarization technique was used to measure the corrosion rate of X52‐sample in simulated solution containing SRB metabolic products species. The curve obtained from LPR data was then fitted using multiple non‐linear regression method by Minitab 15® software.Findings – Statistical analysis shows that sulphide and sulphite have significant effect on the X52 corrosion rate.Originality/value – Using abiotic chemistry approach, an empirical equation that considers SRB metabolic species has been developed. The equation could be used to predict carbon steel corrosion rate by SRB.

Comparison of Corrosion Behavior of Electrochemically Deposited Nano‐Cobalt‐Coated Ni Sheet

Corrosion behavior of nano‐coblat‐coated Ni sheet was compared with pure Ni and 20% Fe‐Ni alloy sheet using potentiodynamic polarization and linear polarization technique in 0.1 M NaCl solution at room temperature. Results showed that corrosion resistance properties of nano‐Co‐coated Ni sheet were almost same as that of pure Ni sheet, however corrosion resistance of 20% Fe‐Ni sheet was decreased significantly. Pitting potential of 20% Fe‐Ni sheet was subsequently decreased as compared to pure Ni sheet as well as nano‐cobalt‐coated Ni sheet. SEM/EDS analysis of the corroded surfaces showed that both pure Ni and nano‐coblat‐coated Ni sheet did not show any appreciable corrosion however significant corrosion was observed in the case of 20% Fe‐Ni sheet.