Early stages of copper corrosion behaviour in a Tunisian soil

The early stages of copper corrosion in a Tunisian soil were studied using mass loss, surface analysis (optical microscopy, visible spectroscopy, IRTF and atomic force microscopy) and electrochemical characterizations (polarization curves and cyclic voltammetry). The corrosion rate dependence with immersion time was Δm = at^b. Two behaviours for the material surface were evidenced when varying the soil concentration and temperature. Then, the apparent kinetic constant, the soil reaction order and the apparent activation energy were calculated. Analytical and electrochemical characterizations showed that a rough patina layer was build up as a result of the interaction between soil and copper.     

Comparison of soil properties measurements in pipeline corrosion estimation

Soil corrosion is a hazardous electrochemical process that affects buried metals in contact with soil. Corrosion in soils resembles atmospheric corrosion with corrosion rates usually higher and depending on the soil type. There are numerous properties of soil and thus soils can be classified in many different ways. Soil resistivity is one of the main indicators of soil corrosivity and thus of the hazardous impact the soil has on metal materials in the soil environment, although it is not the only parameter affecting the risk of corrosion damage. In this study on‐site measurements and laboratory measurements of soil characteristics are performed and compared. On‐site measurements include measuring the redox potential and soil resistivity by Wenner 4‐pin method, while the measurements in the laboratory include measuring soil conductivity, as well as moisture content, pH, content of sulphates, chlorides, and sulfides and polarization measurements, which give the most accurate results. The measurements have shown that if the Wenner 4‐pin method is performed in a convenient way the obtained results are not precise but can give an indicative picture of the corrosivity of the observed soil.     

The effect of CeCl3 inhibitor on the localized corrosion of stainless steel in chloride solutions

Stainless steels have been used extensively in many sectors such as medical and household appliances as well as construction. This has been primarily due to their high resistance to corrosion attacks, reasonable cost, and excellent mechanical properties. However, when placed in corrosive media stainless steel is susceptible to localized corrosion attacks, especially when placed in chloride solutions. The paper explores the issue of corrosion liability of austenitic (AISI 316) and duplex (UNS S32205) stainless steels in et aconditions of seawater environment as well as under the influence of an inhibitor in the same environmental conditions. The behavior of stainless steels was examined via electrochemical testing relying on DC and AC techniques, optical metallographic analysis, scanning electron microscopy, and X‐ray diffraction analysis. Duplex stainless steel showed better resistance to localized corrosion but a higher tendency toward general corrosion in all examined solutions. Cerium chloride in a chloride solution showed inhibiting properties for both the AISI 316 and the UNS S32205.     

The atmospheric corrosion of copper at two sites in Portugal: a comparative study

This paper presents a comparative study on the atmospheric corrosion of copper, at two sites, in Portugal, with exposures started in two different seasons (summer and winter). Particular attention is devoted to the initial stages of the corrosion process.The levels of pollutants, namely of SO₂ and chlorides, in both atmospheres, have been measured, over the periods from August 1999 to July 2000 and from November 2000 until July 2001. Climatic data for both sites and both periods has been collected and analysed.Kinetics of the corrosion process (weight losses) have shown to be described by: Δm=kt^0.6 and Δm=kt^0.4, with k equal to 3.4 (g m⁻² month^−0.6) and 17 (g m⁻² month^−0.4), for the one year exposures, started in summer, at the urban and maritime atmospheres, respectively. Exposures started in winter, at the urban atmosphere, have lead to kinetics described by Δm=kt^0.7 with k=5.0 (g m⁻² month^−0.7).The chemical composition and the morphology of the copper patinas, corresponding to exposures of 2 and 12 months, at the two sites, are compared as well as the morphology of the corroded surfaces.     

Multisecular corrosion behaviour of low carbon steel in anoxic soils: Characterisation of corrosion system on archaeological artefacts

In the context of the prediction of materials behaviour used in the nuclear waste storage, the understanding of iron corrosion mechanisms in anoxic environment is of great importance. Information can be obtained using complementary analytical tools. Interactions between burial soil and archaeological artefacts are studied by performing on site soil measurements. Moreover, archaeological artefacts are studied on transverse sections using a combination of microbeam techniques. The specific interest of this project lies in the study of ferrous thick corrosion layers formed in anoxic environments.     

Electrochemical impedance spectroscopy study of surface films formed on copper in aqueous environments

The electrochemical behavior of pure copper has been studied in aqueous environments using linear polarization and electrochemical impedance spectroscopy (EIS) techniques as a function of immersion time. The effect of pollutants (like chloride, sulfide and ammonium ions) on the nature of films formed on the copper surface has been studied. All the surfaces revealed the presence of a porous oxide layer. The corrosion resistance decreased with increasing amount of chloride ions. The addition of Na₂S in the environments in the absence of any chloride species was beneficial for corrosion resistance. EIS data suggested that the capacitance of the films formed in chloride environments was higher. The surfaces obtained in presence of chloride ions were relatively rough and deeply attacked. The total impedance decreased after 432 h of immersion in solutions possessing chloride ions. The damaging role of chloride ions and the relatively less severe effect of sulfide ions were noted.     

Corrosion behaviour of Ti–Ta–Sn alloy systems in 0.9% NaCl solution

Two alloys of varying contents of tantalum (Ta) and tin (Sn) were prepared and homogenized to evaluate their microstructural and electrochemical characteristics. The microstructural features were revealed through optical microscopy and X‐ray diffraction methods. The formation and stability of passive film was studied by open circuit potential, potentiodynamic polarization and electrochemical scratch tests. The electrochemical impedance spectroscopy results simulated with equivalent electrical circuit suggested bilayer structure of outer porous and inner barrier oxide films. The quantitative data showed thick inner barrier oxide film retarded electrochemical reactions at low ‘Ta’ and ‘Sn’ concentration. The increased percentage of ‘Ta’ and ‘Sn’ deteriorated barrier properties by agglomeration of Ta₂Sn₃ and Ta_0.15Ti_0.85 precipitates within grains and at the grain boundaries.     

Corrosion behavior of SRB Desulfobulbus propionicus isolated from an Indian petroleum refinery on mild steel

In this study, Desulfobulbus propionicus (D. propionicus), a sulfate reducing bacterium (SRB) was isolated and identified in cooling towers by molecular biologic techniques. This bacterial species has been reported for the first time in the cooling towers of an Indian petroleum refinery. Corrosion behaviors were analyzed by electrochemical and weight loss methods. The high corrosion rate and the enhancement of anodic current in increased chloride environment was noticed in the presence of D. propionicus indicating that this SRB species enhances the pitting corrosion of mild steel. Propionate metabolism in H₂S production is discussed as a new pathway of corrosion enhancement.     

Assessment of the interphase behaviour of two bronze alloys in archaeological soil

The aim of this work is to evaluate the behaviour of bronze in archaeological soil by gravimetric study, electrochemical research and analytic survey. Archaeological soil samples were collected from Jama that date back to the second Punic war. Mineralogical, micro‐structural, micro‐morphological and chemical analyses of soil constituents were performed. The bronze samples correspond to Cu‐9.4Sn (B₁) and Cu‐7.7Sn with 1% of Pb (B₂). The open circuit potential value recorded for B₂/corrosion product/soil is stable after only 7 min due to its reactivity allowing to a rapid development of a protective corrosion layer. The B₂ interphase is more developed and stable than B₁. Under anodic polarisation, the B₂ alloy corrodes less than the B₁ alloy owing to its lower anodic current. Based on the EIS study, two evolution stages of the bronze alloy/corrosion product/soil interphase are detected. For the first stage, the interphase is equivalent to two R//C loops at high and medium frequencies, respectively related to the corrosion layer and charge transfer process, associated to mass transport phenomena. For the second stage, the resistance of corrosion layer decreases and the first loop vanishes. SEM‐EDS analysis demonstrate that the first stage (20 days of immersion) can be characterized by a well covered surface with a thin corrosion product, the external layer exhibits low tin content. However, after 310 days of immersion, the surface state is different with isolated particulates composed by Cu and soil compounds on a cracked layer with the presence of craters showing an internal layer.     

Correlation of stress corrosion cracking behaviour with electrical conductivity and open circuit potential in Al‐Li‐Cu‐Mg‐Zr alloys

Studies of stress corrosion cracking (SCC) behaviour by slow strain rate test (SSRT), potentiodynamic electrochemical polarization and measurement of electrical resistivity were carried out on 8090 and 1441 Al‐Li‐Cu‐Mg‐Zr alloys in their peak aged T8, over aged T7 and retrogressed and reaged (RRA) T77 tempers. It has been found that the SCC resistance is maximum in the T7 temper, least in the T8 temper and in the RRA T77 tempers it lies in between to that of the T8 and T7 tempers, indicating that RRA heat treatment given to the T8 temper of both alloys caused an improvement of SCC resistance. Further, studies on the electrical conductivity measurements and electrochemical polarization of all tempers of both alloys showed that T7 temper has maximum electrical conductivity and most negative (anodic) open circuit potential (OCP), T8 has the minimum and the least respectively, whereas, in the T77 tempers these values lie in between to those of the T8 and T7 tempers. Therefore, a definite pattern of variation of these results with RRA treatment draws an attention to correlate SCC behaviour, electrical conductivity and OCP values which are explained on the basis of microstructural features revealed by TEM and XRD studies.     

Oxidation of tungstate‐containing green rust (Cl–) in aqueous solution

The influence of tungstate on the oxidation of green rust [GR(Cl^–)], which contains both Fe(II) and Fe(III), was investigated by synthesizing suspensions of GR(Cl^–) containing tungstate and oxidizing them via injection of N₂ gas containing O₂. XRD and TEM analyses were used for characterizing the solid particles formed during synthesis and oxidation. The results showed that the formation of fine α‐FeOOH was enhanced by the addition of tungstate to the GR(Cl^–) suspensions, while GR(Cl^–) without tungstate was transformed primarily into γ‐FeOOH. The pH, oxidation‐reduction potential (ORP), and dissolved oxygen (DO) values of the aqueous solution were measured during oxidation of GR(Cl^–) with and without tungstate. The results showed that whereas the pH value of the solution was decreased and the ORP value was increased monotonically by oxidation of GR(Cl^–), the pH and ORP values during oxidation the GR(Cl^–) suspension containing tungstate revealed characteristic changes with time. XAS was also used for characterizing the chemical state and local structure of tungstate in the oxidized particles. The results indicated that the local structure of WO was essentially retained in the particles precipitated from GR(Cl^–) suspensions.     

Inhibition of copper corrosion by 1,2,3-benzotriazole: A review

Benzotriazole (BTAH) has been known for more than sixty years to be a very effective inhibitor of corrosion for copper and its alloys. In spite of numerous studies devoted to the investigation of BTAH action, the mechanism of its action is still not completely understood. The aim of this review is to summarize important work in the field of BTAH as a copper corrosion inhibitor, from the early discoveries to the present time. Special attention is given to the BTAH surface structure. The disagreement between findings and mechanisms is discussed.     

Electrochemistry and XPS study of an imidazoline as corrosion inhibitor of mild steel in an acidic environment

The effect of 2‐(2‐heptadec‐8‐enyl‐4,5‐dihydro‐imidazol‐1‐yl)‐ethylamine on the corrosion behavior of mild steel in aqueous hydrochloric acid was investigated using weight loss measurements, polarization scans, electrochemical impedance, and X‐ray photoelectron spectroscopy (XPS). The inhibition efficiencies and coverage degrees increased with the concentration of inhibitor but decreased proportionally with temperature. It appears that the steric hindrance of the aliphatic chain on the imidazoline ring adsorption may affect inhibitor efficiency. Polarization curves showed that the oleic imidazoline (OI) acted essentially as a mixed type inhibitor, in which the blocking of active sites occurred. As a result of film formation, impedance spectra revealed a considerable increase in the charge transfer resistance as indicated by the second capacitive loop. XPS depth profile analysis observed the presence of nitrogen and carbon species on the inhibitor film, which were associated to the OI.     

Sea water corrosion behaviour of T2 and 12832 copper alloy materials in different sea areas

ABSTRACT

Field exposure test was carried out to investigate the sea water corrosion behaviour and rules of T2 and 12832 copper alloy materials in different sea areas. The corrosion morphology characteristics and corrosion products properties were analysed using different techniques, and the main environmental factors influencing their corrosion rates were discussed by applying grey relational analysis. Reaults showed that with the decrease of the latitude, the corrosion rate of T2 increased, and grey relational analysis indicated that temperature had a significant influence on it. For 12832 copper alloy, the corrosion rate was lower than that of T2 on the whole. Different degree of biofouling occurred on 12832 copper alloy, and the surface fouling conditions (including sediment deposition) had a crucial impact on its corrosion behaviour. In summary, 12832 copper alloy had a better corrosion resistance, but accompanied by de-Mn and de-Al corrosion.     

Morphology of corrosion products of steel in concrete under macro‐cell and self‐corrosion conditions

In this paper investigations into the formation of specific corrosion products during the process of chloride induced corrosion of steel in concrete are presented. The extension of corrosion products within concrete was established by means of X‐ray tomography analyses. Then a detailed analysis of the nature of corrosion products has been conducted by means of Raman micro‐spectroscopy and energy dispersive spectroscopy. Results emphasize two different corrosion patterns. The first one is composed of shallow cavities, where mostly magnetite and goethite were identified, traducing aerated to moderate aerated conditions in these media. The second pattern was identified as deep, needle‐like pits, where chlorinated‐iron‐oxides phases were present associated with more or less important chloride enrichments. The presence of these particular species is indicating low redox and low pH conditions within these pits.