Open Circuit Corrosion Potential Research Articles

Study on tribocorrosion properties of cold spray additively manufactured 2024 Al alloy

This study was conducted with a high level of thoroughness. X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM) were used to analyze the phase composition and microstructure of the AM-2024Al and the RO-2024Al. The hardness and porosity of the AM-2024Al, as well as the bonding strength between AM-2024Al and RO-2024Al, were also investigated. Furthermore, the corrosion and tribocorrosion properties and failure mechanisms of the AM-2024Al and the RO-2024Al were systematically and thoroughly compared and analyzed. The results of this comprehensive study revealed that the AM-2024Al displayed a similar phase structure and higher hardness in comparison to the RO-2024Al, and the AM-2024Al was compact and tightly bound to the RO-2024Al with a bonding strength of over 55.5 MPa. Furthermore, the AM-2024Al exhibited better corrosion resistance under PDP (potentiodynamic polarization) corrosion and similar wet sliding wear resistance under an approximate pure friction process (OCP corrosion, namely open circuit potential corrosion) and tribocorrosion compared with the RO-2024Al. These findings provide a high level of confidence in the potential of cold spraying additive manufacture 2024Al as a reliable way to repair damaged RO-2024Al.

Mechanism of inhibitory action of fruit cake extracts as a new environmentally inhibitors of carbon steel corrosion

In this study the firstly study reported on the use of plum, cherry, nectarine and apple pomace extract as corrosion inhibitors of steel in water solution. Potentiodynamic polarization study showed that extracts act as a mixed type inhibitors with dominant cathodic effect. Linear polarization resistance method (LRP) assesses the time-related effect of inhibitors during open circuit potential corrosion. The results show that the inhibitory efficiency of our extract increases with increasing time formation protective film to reach 99 % in a concentration of 500 ppm. LC - MS and FTIR spectroscopy techniques can be concluded that several water-soluble interaction products of chemical reaction in NaCl are identified namely flavanol–anthocyanin and flavanol-aldehyde adducts. Subsequently, the iron-mediated complexation and oxidation of the extract components (flvonoids) in the aqueous solution were explored using UV-spectrophotometric and HPLC methods. With the passage of time, iron-mediated oxidative degradation and coupling reactions occurred, resulting in the production of hydroxybenzoic acid derivatives. Consequently, the inhibition decreased after 24 h. The chemisorption type of interaction of the product formed in the inhibited solution forming the adsorption-polymerization layer with the steel surface is established. Based on the quantum-chemically calculated parameters of the electronic structure of flavanol–anthocyanin and flavanol-aldehyde adducts, it was established for the first time that the combination of reactive fragments in them, which are spatially located in different planes with a higher quantity of hydroxyl groups, increases their adsorption activity and, as a result, their inhibitory capacity.

The microwave absorption and anti-corrosion performance of flaky FeSiCr powder coated by silane film

A silane film was prepared on the surface of flaky FeSiCr powder by sol-gel method. The phase and morphology of the samples were observed by X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM), and the valence state and chemical composition of the elements were determined by X-ray Photoelectron Spectroscopy (XPS). The results showed that the observed images of homogeneous silane films confirm the successful preparation of lamellar FeSiCr@PFOTMS composites. The electromagnetic parameters measurement results showed that the complex permittivity of the samples is substantially reduced and the complex permeability changes little, then the balance of electromagnetic parameters is improved and the impedance matching is optimized. When PFOTMS is added in amounts up to 2 mL, the FeSiCr@PFOTMS composites showed the best microwave energy absorption and corrosion resistance. The minimum reflection loss value of the sample reached –32.22 dB at 2.16 GHz. The electrochemical test results showed that the open circuit corrosion potential of FeSiCr@PFOTMS composites with 2 mL PFOTMS increased from –0.217 V to 0.031 V, and the corrosion voltage increased from –0.215 V to 0.028 V. These results provide ideas for the preparation of multifunctional composites with both excellent microwave absorption properties and corrosion resistance in practical applications.

Liberación de iones de aleaciones dentales no preciosas en la cavidad oral

ABSTRACT Dental alloys in the oral cavity release ions by corrosive action of saliva, which are deposited in the lower part of the mouth, others diffuse through the gums and most of them pass to the gastrointestinal system. In the present work, nine dental alloys frequently used in our country by people with low resources (316L stainless steel, low and high copper silver amalgams, Co-Cr and Ni-Cr alloys, Cu and Ti-6Al-4V base alloys). Its open circuit corrosion potential was measured, its potentiodynamic polarization curves were plotted and corrosion products were analyzed by EDAX, finding Hg, Ag, Ni, Co, Cu, Zn and Si ions, which can affect the health of users, so it is recommended that dentists and dental technicians inform patients who suffer from hypersensitivity do not use alloys containing potentially allergic metals.

5 years of in situ reinforcement corrosion monitoring in the splash and submerged zone of a cracked concrete element

Results of more than 5 years of in situ reinforcement corrosion monitoring are presented including continuous measurements of concrete resistivity, temperature, and open circuit corrosion potential measurements. Depth dependent resistivity and temperature measurements were obtained by means of multi-ring electrodes, while so-called instrumented rebars were used for location- and time-dependent open circuit corrosion potential measurements. The presented results highlight the complex interaction between mass transport, fracture, exposure, and electrochemistry and underline the importance of in situ measurements, which are imperative for model testing to enable accurate and reliable long-term performance predictions of reinforced concrete structures.

ARTIGO RETRATADO

ABSTRACT In this work, the open-circuit corrosion potentials of the alloys studied in aerated artificial saliva were determined; in the same solution, the potentiodynamic polarization curves of said alloys have been drawn. The corrosion potentials and current intensities of the galvanic coupling of the Ti-6Al-4V alloy with the Co-Cr and Ni-Cr alloys were determined using the Evans method, finding that the galvanic couples more resistant to corrosion in the electrolytic medium considered are those formed between the Ti alloy and the Co-Cr alloys; the least resistant are those formed between Ti alloy and Ni-Cr alloys. The corroded surfaces of the seven alloys considered in this work were also studied, and by EDAX the corrosion products due to the ions detached in the electrolytic medium were analyzed.

Corrosion inhibition study of beta-dimethylaminoethyl alcohol on low carbon steel in 0.5 M HCl electrolyte

Beta-dimethylaminoethyl alcohol was investigated for its inhibition performance on low carbon steel corrosion in 0.5MHCl solution. Results show the organic compound effectively suppressed the redox electrochemical mechanism responsible for corrosion with highest inhibition value of 89.07% and 97.05% from weight loss measurement and potentiodynamic polarization technique. Polarization plots exhibited significant passivation characteristics at higher concentrations of the alcohol in the acid solution. Open circuit corrosion potential measurements depict values within passivity potentials. Thermodynamic calculations show the molecules of the alcohol adhered onto the steel surface through physiochemical to chemisorption reaction processes with respect to Langmuir and Freundlich isotherms models. The compound exhibited cathodic type inhibition properties. Scanning electron microscopy confirmed the significant surface deterioration with visible corrosion pits, grooves and cracks on the control steel. This significantly contrasts the improved morphology of the inhibited steel. X-ray diffractometry confirmed both the absence of corrosion products and phases after exposure in the amino alcohol.

Reinforcement corrosion in limestone flash calcined clay cement-based concrete

Limestone calcined clay cement (LC3) concrete has attracted world-wide attention as a newly promising low-carbon concrete. In this study, long-term reinforcement corrosion in LC3 concrete was investigated. Both chloride and carbonation-induced reinforcing bar corrosion were examined. Open circuit corrosion potential, polarization resistance, Tafel constants were monitored at regular intervals up to 500 days. Gravimetric mass loss was measured and compared to the loss of mass calculated using electrochemical methods. The performance of concrete with flash calcined clay and limestone was similar to that of traditional Portland cement concrete in long-term investigation. Traditional corrosion methods and classifications used widely to assess of steel in concrete can be applied to concrete containing LC3 providing a recalibration of polarization resistance range for passitivity condition.

Wear and corrosion behavior of coconut shell ash (CSA) reinforced Al6061 metal matrix composites

Abstract The wear and electrochemical corrosion behavior of Al6061-CSA composites with varying weight percentages of CSA reinforcement have been investigated. A pin on disc apparatus was used to characterize the wear resistance of the prepared composite specimens. Open-circuit corrosion potential (OCP) and potentiodynamic polarization measurements (PDP) were used to study the corrosion behavior of prepared Al6061-CSA composites in 3.5 % NaCl solution. The characterization was performed through EDS and SEM. The wear rate of the composites decreased with increase in wt.-% of the CSA. It was observed that with an increase in CSA, the coefficient of friction and friction force of the composites increased. The composites produced have better corrosion resistance than the base matrix aluminum alloy Al6061. The corrosion resistance of the composites starts to increase with an increase in CSA content up to 6 wt.-%, and then it starts decreasing. FSEM and XRD analysis were performed on the morphology of composites in 3.5 % NaCl solution.

Chemical Imaging of Reactive Surfaces Using Microsensors As Tips in Scanning Electrochemical Microscopy: Applications in Corrosion Research and Protection

Chemical imaging of reactive surfaces with high spatial resolution has become available with the introduction of scanning electrochemical microscopy (SECM). In fact, this technique has become a powerful tool in the study of a wide range of corrosion processes. This presentation provides a brief review on the applications of scanning electrochemical microscopy (SECM) in measuring, characterising and evaluating corroding systems as developed in our research group at the University of La Laguna (Spain). Localized corrosion processes and electrochemical activity distributions in surfaces can thus be investigated in real time with high spatial resolution. The SECM is a unique near-field scanning technique that is electrochemically integrated as to detect chemical and electrochemical activities in electrochemical heterogeneous systems such as those operating in corrosion research. The SECM can be used in a variety of ways, which can be broadly classified into amperometric and potentiometric modes, depending on the type of the sensing probe, namely an ultramicroelectrode (UME) and an ion-selective microelectrode, respectively. Because the corroding metal usually involves local changes in ionic concentrations, as they produce Mz+ at the anodic sites transferred under diffusion control, the system can be studied by amperometric SECM. This feature has been exploited to image the generation of specific metal cations for the visualization of metastable pits on austenitic steel [1], and the detection of metal dissolution either from inclusions in alloys [2], or from defects in polymer-coated metals [3]. Additionally, in a neutral aqueous media, the reaction of dissolved oxygen from the electrolyte at the cathodic areas may be analyzed through the monitoring of the subsequent depletion of oxygen content in the solution volume adjacent to the cathodic sites [4]. However, for the detection of concentration distributions in certain corroding samples, especially for metals with sufficiently negative redox potentials in aqueous environments, the use of Pt microelectrodes is limited by the onset of oxygen reduction and hydrogen evolution reactions [5]. Though less employed, these physicochemical parameters may be studied using ion-selective electrodes (ISEs) as tips. In this case, the SECM is operated in the potentiometric mode, which gives greater chemical selectivity. In this respect, the applicability of Zn2+ [6] and Mg2+ ion-selective microelectrodes [7] with SECM has been established, although the onset of high electric fields in the electrolyte phase associated to galvanic corrosion [8] requires new tip assemblies for accurate monitoring [9]. In this contribution, the operation modes of the instrument are briefly described together with typical experiments selected to illustrate their application in sensing localized corrosion. Selected examples regarding the characterization of corrosion processes using scanning electrochemical microscopy are presented, including passivity breakdown and pit initiation, galvanic coupling, and blistering and delamination processes in coated metals. [1] Y. González-García, G.T. Burstein, S. González, R.M. Souto. Imaging metastable pits on austenitic stainless steel in situ at the open-circuit corrosion potential. Electrochemistry Communications 6, 637-642 (2004). [2] J. Izquierdo, S. González, R.M. Souto. Application of AC-SECM in corrosion science: Local visualization of heterogeneous chemical activity in AA2024 surfaces. International Journal of Electrochemical Science 7, 11377-11388 (2012). [3] R.M. Souto, Y. González-García, S. González. In situ monitoring of electroactive species by using the scanning electrochemical microscope. Application to the Investigation of degradation processes at defective coated metals. Corrosion Science 47, 3312-3323 (2005). [4] J.J. Santana, J. González-Guzmán, L. Fernández-Mérida, S. González, R.M. Souto. Visualization of local degradation processes in coated metals by means of scanning electrochemical microscopy in the redox competition mode. Electrochimica Acta 55, 4488-4494 (2010). [5] R.M. Souto, Y. González-García, D. Battistel, S. Daniele. In situ SECM detection of metal dissolution during zinc corrosion by means of mercury sphere-cap microelectrode tips. Chemistry, A European Journal 17, 230-236 (2011). [6] J. Izquierdo, L. Nagy, Á. Varga, I. Bitter, G. Nagy, R.M. Souto. Scanning electrochemical microscopy for the investigation of corrosion processes: measurement of Zn2+ spatial distribution with ion selective microelectrodes. Electrochimica Acta 59, 398-403 (2011). [7] J. Izquierdo, A. Kiss, J.J. Santana, L. Nagy, I. Bitter, H.S. Isaacs, G. Nagy, R.M. Souto. Development of Mg2+ ion-selective microelectrodes for potentiometric Scanning Electrochemical Microscopy monitoring of galvanic corrosion processes. Journal of The Electrochemical Society 160, C451-C459 (2013). [8] A. Kiss, D. Filotás, R.M. Souto, G. Nagy. The effect of electric field on potentiometric Scanning Electrochemical Microscopic imaging. Electrochemistry Communications 77, 138-141 (2017). [9] D. Filotás, B.M. Fernández-Pérez, A. Kiss, L. Nagy, G. Nagy, R.M. Souto. Double barrel microelectrode assembly to prevent electrical field effects in potentiometric SECM imaging of galvanic corrosion processes. Journal of The Electrochemical Society 165, C270-C277 (2018).

Excellent mechanical, tribological and anti-corrosive performance of novel Ti-DLC nanocomposite thin films prepared via magnetron sputtering method

Ti-doped diamond-like carbon nanocomposite thin films with different Ti contents are prepared by closed field unbalanced magnetron sputtering. Designed Ti target current increases from 0.3A to 1.0A. The effect of Ti content on microstructures and properties is investigated. The phases of nano-TiC and amorphous carbon are confirmed. The film (containing less than 50% sp3 C content) deposited with a Ti target current of 0.4A obtains the highest hardness of 44.6 GPa, which is rarely reported. Besides, the film with a Ti target current of 0.3A exhibits the lowest the friction coefficient of 0.02 and 99.10% reduction in wear rate compared with the untreated specimen due to its lubricating effect and the gradient multilayer structure. Moreover, the films have a high open-circuit corrosion potential, a low anodic current density and a wide passivation range, indicating its enhanced corrosion resistance. Most importantly, these inspiring results demonstrated that the excellent mechanical, tribological and anti-corrosion properties can be realized simultaneously by introducing the as-deposited films with the merits of high hardness, self-lubricating and chemical inertness.

Influence of final annealing temperature on the microstructural evolution and corrosion resistance of a Sandwich multi-layered aluminum sheet

The effects of final annealing temperature on the microstructure and corrosion resistance of a sandwich (4343/3z23a/4343) multi-layered Al sheet were investigated by optical microscopy, tensile test, Scanning electron microscope (SEM), and Glow discharge optical emission spectrometry (GDOES). It was found that high temperature (460 °C) final annealing significantly improves the brazing ability of 4343/3z23a/4343 multi-layers Al sheets, and eliminates erosion of core layer during brazing. During brazing, Si diffuses from the clad layer to the core layer and Cu diffuses from the core layer to clad layer. Si/Cu segregate at the surface of re-solidified clad layer after brazing. The segregations of Si/Cu at the surface of clad layer after brazing lead to that the open-circuit corrosion potential of the Al sheets increases by 25 mV. The main corrosion mechanism of nonbrazed materials is pitting, while the dominant corrosion mechanism for brazed materials is intergranular corrosion.

Electrochemical analysis of the corrosion inhibition effect of trypsin complex on the pitting corrosion of 420 martensitic stainless steel in 2M H2SO4 solution.

Inhibition effect of trypsin complex (TC) on the pitting corrosion of martensitic stainless steel (type 420) in 1M H2SO4 solution was studied with potentiodynamic polarization, open circuit potential measurement and optical microscopy. TC reduced the corrosion rate of the steel with maximum inhibition efficiency of 80.75%. Corrosion potential shifted anodically due to the electrochemical action of TC. The pitting potential increased from 1.088VAg/AgCl (3M) at 0% TC to 1.365VAg/AgCl(3M) at 4% TC. TC shifts the open circuit corrosion potential from -0.270s at 0% TC concentration to -0.255V at 5% TC. The compound completely adsorbed onto the steel according to Langmuir, Frumkin and Temkin isotherms. ATF-FTIR spectroscopy confirmed the inhibition mode to be through surface coverage. Thermodynamic calculations showed physisorption molecular interaction. Corrosion pits are present on the uninhibited 420 morphology in comparison to TC inhibited surface which slightly deteriorated.

Transient Changes of Corrosion Potentials and Their Correlations with Metal Release During Stagnation and Flow Episodes in Drinking Water Systems

Corrosion and metal release in drinking water systems are affected by the chemistry of ambient water (e.g., pH, concentrations of carbonate and other ions), stagnation/flow transitions associated with diurnal and seasonal changes of water consumption as well as the introduction of alternative water sources, for instance desalinated water. Control of metal release in drinking water is mandated by the EPA within the Lead and Copper Rule (LCR). The current LCR paradigm of copper and lead monitoring is based on measurements of metal concentrations at the end of a predetermined stagnation time (e.g., > 6 hours). While this approach is suitable for the general evaluation of LCR compliance, it does not provide any information concerning metal release in short-term stagnation episodes nor does it allow evaluating effects of short-term changes of water chemistry. The goal of this study was to address these deficiencies based on the quantitation of transient changes of open circuit corrosion potentials (Ecorr) of metal surfaces during stagnation/flow episodes and examining relationships between such changes and attendant metal release at varying water chemistries. Experimental data demonstrate that Ecorr transients for copper, lead and iron are characterized by several consistently present features. Theoretical interpretation shows that the Ecorr transients are associated with the concurrent processes of release of metal solutes and consumption of oxidants (dissolved oxygen, chlorine species). The former process is dominant in the case of copper or lead while the latter effect is more significant for higher corrosion rates typical for iron. Further modeling shows the presence of the phase of rapid quasi-exponential consumption of the oxidants at the surface followed by a slower phase associated with the development of diffusion controlled fluxes. These results show that the monitoring of Ecorr transients allows quantitating corrosion and metal release rates in conditions characteristic for drinking water systems, notably when other methods either do not provide relevant data or cannot be deployed.

Distribution of Corrosion Potentials across Galvanically Coupled Interfaces Exposed in Drinking Water

Control of lead release from lead-containing materials galvanically coupled with copper or bronze represent a challenge for corrosion engineers and water treatment practitioners. Currently available data show that in some situations galvanically coupled lead remains passivated and releases little metal while in other cases, for instance those associated with changes of ambient water chemistry, previously passive coupled lead becomes active with resultant episodes of elevated lead release. While this problem has been thoroughly investigated on a phenomenological level, current understanding of the electrochemistry of galvanic stimulation of lead corrosion and release in drinking water remains insufficient. The goal of this study was to quantify changes of the open circuit corrosion potential (Ecorr(x)) across lead/copper interfaces as a function of the distance from the galvanic juncture and concentrations of background salts such sodium chloride, carbonate and others. The theory developed by Song et al. 2010 provides a detailed mathematical description of the distribution of Ecorr across galvanic interfaces but this theory has been developed and rested for systems that are notably different from those typical for drinking water. Measurements of trans-galvanic interface Ecorr profiles performed in this study showed that Ecorr(x) profiles conformed to predictions made based on the existing theory and the effective length of the longitudinal penetration of ionic currents increased as a square root of solution conductivity. The effective length of the coupled ionic currents was notably different for copper and lead. The data demonstrate that short- and long-term changes of properties of ambient water can cause Ecorr(x) to undergo considerable changes. This can potentially induce shifts of the galvanically affected zone in which accelerated lead release takes place. Further studies are needed to examine actual effects of such Ecorr(x) shifts on spatially localized lead release from galvanically coupled lead-containing materials. Song, G. L. (2010). Potential and current distributions of one-dimensional galvanic corrosion systems. Corrosion Science, 52(2), 455-480

Chloride-induced corrosion of reinforcement in low-calcium fly ash-based geopolymer concrete

Geopolymer concrete (GPC) has significant potential as a more sustainable alternative for ordinary Portland cement concrete (PCC). However; as a rather new engineering material, there are some concerns over the durability aspects of geopolymer-based binders. In this study, the performance of chloride-contaminated reinforced GPC specimens manufactured using a blended low-calcium fly ash and slag cement is investigated by long-term monitoring of corrosion parameters such as open circuit corrosion potential, polarization resistance and Tafel slopes. The electrochemical results are validated by contrasting the electrochemical mass losses with the mass losses obtained from the gravimetric measurements. The investigated low-calcium fly ash-based GPC exhibit a comparable electrochemical performance to a similar strength PCC during the propagation phase of corrosion. Additionally, some of the conventional classifications which are commonly used to assess the severity of corrosion in Portland cement-based corroding systems might need some recalibration to be used for low-calcium fly ash-based corroding systems.

Electrodeposition, characterization and corrosion investigations of galvanic tin-zinc layers from pyrophosphate baths

Tin-zinc alloy deposits are recognised as a potential alternative to toxic cadmium as corrosion resistant coatings. Tin-zinc alloy layers offer outstanding corrosion protection for steel by combining the barrier protection of tin with the galvanic protection of zinc. Tin-zinc coatings have been used on the chassis of electrical and electronic apparatus and on critical automotive parts such as fuel and brake line components. In this study, tin-zinc alloy deposits were successfully prepared from alkaline, pyrophosphate-based electrolytes. The plating process gives a compact and fine grained deposit. The desired proportions of tin and zinc in the deposited alloy are determined by the bath composition and the operating conditions during plating. Three electrode systems were used for the electrochemical investigation. The mechanism of Sn-Zn electrodeposition was studied by linear and cyclic voltammetry. The corrosion parameters, including open-circuit potential-time curves, corrosion potential and corrosion current density of electrodeposited tin-zinc alloys of different compositions have been examined in a brine medium containing 3 wt. % NaCl. The corrosion resistance depends on the plating composition. The Sn-28Zn deposit showed the best anticorrosive properties.

The Influence of the Chemical Composition on the Corrosion Performances of Some Al-Fe-Si, Al-Mg-Si and Al-Mg-Mn Type of Alloys

Paper presents the results on the corrosion behavior of some Al-Fe-Si, Al-Mg-Si and Al-Mg-Mn alloys in their final commercially usable tempered state. Durability of alloys was quantified and compared in the sense of corrosion rates in aqueous solutions while also having in mind the role of alloy chemistry. Open circuit corrosion potential (OCP) measurements, linear polarization and potentiodynamic anodic/cathodic polarization was employed in order to determine the corrosion behavior of samples in the mixture of chloride ions containing aqueous corrosion ambient. We found out that AlFe0.83Si0.18(AA8079), AlMg0.63Si0.72 (AA6005) and AlMg4Mn (AA5182) alloy exhibited the highest rates of passivation in 0.51 mol NaCl solution. The group of Al-Fe-Si alloys exhibited the greatest sensitivity to the changes in chemical composition under potentiodynamic polarization. Artificially aged Al-Mg-Si extruded profiles and fully annealed (after cold rolling) Al-Mg-Mn sheets exhibit very similar levels of equilibrium potentials E(I=0) in 0.51 mol NaCl solution. In the case of Al-Fe-Si alloys, we found that Fe/Si ratio also plays an important role, next to the total content of Fe and Si. Alloys with high Fe/Si ratios showed almost 30 % lower polarization resistance compared to the alloys with balanced Fe/Si, even in the case of the equal total content of alloying elements. The AlMg0.7Si1.2Mn0.8 alloy aged after quenching in the sprayed water and AlMg4Zn1.3Mn0.4 annealed sheet exhibit very similar levels of corrosion rates in 0.51 mol NaCl solution.

The influence of the chemical composition and type of alloy on corrosion performances of some medium strength Al-Mg-Si series of alloys

The effect of the chemical composition, i.e. content of silicone (Si) and other alloying elements (Zr, Mn, etc) on the corrosion behaviour and mechanical properties of Al-Mg-Si (6xxx) type alloys was investigated in this paper. Open circuit corrosion potential (OCP) measurements, linear polarization and potentiodynamic anodic/cathodic polarization were employed in order to determine the corrosion behaviour of artificially aged Al-Mg-Si samples in the chloride ions containing aqueous corrosion solutions. The difference in OCPs for the tested 6xxx type alloys in relation to the standard AA1020 alloy was observed to be between 1-4%, except for the AlMg0.65Si0.76Zr0.1 alloy when the difference was 14% (about 100 mV). The presence of zirconium and manganese in AlMgSi0.7 base alloy, that contains small excess of Si, shifts the OCPs to more negative values for -15 mV (~2%) and -88 mV (~11%) in natural water and 0,51 mol NaCl, respectively. All the tested 6xxx type alloys, except AlMg0.7Si1.2Mn0.8, show almost the same corrosion rates and other corrosion characteristics in chloride solution, with mass loss per year between 2.3-3 g/m2 .

Inhibition of AA2024-T351 Corrosion Using Permanganate

The inhibition of corrosion on AA2024-T351 in NaCl solutions, mitigated by either in-situ permanganate ions (MnO4−) or permanganate pretreatment, was examined. Both room temperature pretreatment and solution phase additions were studied as a function of inhibitor concentration. The roles of the inhibitor during anodic and cathodic polarizations were investigated. Inhibition of corrosion at open circuit corrosion potential (OCP) under conditions where anodic and cathodic reactions are coupled was also examined. The oxidation states of the manganese oxides that contributed to protection were determined using potentiometric electrochemical reduction and in-situ Raman spectroscopy. The thermodynamics of the Mn-water system was also considered over a range of concentrations. Permanganate was shown to be both an anodic and cathodic inhibitor, and an inhibitor of copper replating at OCP.