A study on synergistic effect of chloride and sulfate ions on copper corrosion by using electrochemical noise in asymmetric cells

Corrosion of Q235 carbon steel induced by sulfate-reducing bacteria in groundwater: corrosion behavior, corrosion product, and microbial community structure

Microbiologically influenced corrosion (MIC) is one of the reasons leading to the service failure of pipelines buried in the soil. In this work, the effect of sulfate-reducing bacteria (SRB) on the corrosion behavior of Q235 carbon steel in groundwater was investigated by electrochemical methods, surface analysis, and biological analysis. The results show that SRB utilizes iron as electron donor to sustain the vital activities of organic carbon-starved groundwater during the 14-day experimental period. The microbial community composition analysis at the genus level demonstrate that the diversity and richness decrease after corrosion, and the dominant SRB species has changed from Desulfovibrio to Desulfosporosinus. Moreover, the impedance of the carbon steel in the presence of biofilm was 1 order of magnitude higher than that of other periods in the electrochemical test, indicating that the biofilm and formed ferrous sulfide layer impeded the occurrence of corrosion. Although the 3D topography indicated that the surface of carbon steel was more uneven and pits were increased in the presence of SRB, the average weight loss (0.0396 ± 0.0050 g) was much higher than that without SRB (0.0139 ± 0.0007 g). These results implied that the growth of SRB makes the corrosion process of Q235 carbon steel more complicated.

A Review of Electrochemical Techniques for Corrosion Monitoring - Fundamentals and Research Updates

Interculturally, corrosion has been counted as one of the most expensive factors toward the retrogression of concrete and metallic structures resulting in huge monetary losses and unanticipated loss of life. To a large extent, corrosion-related catastrophes can be avoided by having the ability to monitor corrosion before structural integrity is jeopardized. This paper critically reviews the various accustomed electrochemical techniques utilized for corrosion monitoring in terms of their definition, timeline, experimental set-up, advantages, and shortcomings. Additionally, literature exploiting these techniques as their corrosion detection technique has been focused on here. Furthermore, a comparison between recently reported methods has been made to provide better insights into the research progress in this arena.

The influence of calcium on copper corrosion and its by-product release in drinking water

Copper is a high-quality material commonly used in drinking water supply pipes. Calcium is a prevalent cation found in drinking water. However, the effects of calcium on copper corrosion and its by-product release remain unclear. This study discusses the influences of Ca²⁺ on copper corrosion and its by-product release in drinking water under different conditions of Cl^-, SO₄^2-, and Cl^-/SO₄^2-, using electrochemical and scanning electron microscopy techniques. The results indicate that Ca²⁺ slows down the corrosion reaction of copper to some extent in comparison with Cl^-, and the E_corr shifts positively by 0.022 V, while I_corr decreases by 0.235 μA cm^-2. However, the by-product release rate increases by 0.5 μg cm^-2. The addition of Ca²⁺ causes the anodic process to become the controlling factor for corrosion, with an increase in resistance observed in both the inner and outer layers of the corrosion product film through SEM analysis. The corrosion product film becomes denser due to the reaction between Ca²⁺ and Cl^-, forming a product that inhibits the entry of Cl^- into the passive film on the copper surface. Adding Ca²⁺ promotes copper corrosion with the help of SO₄^2- and the release of corrosion by-products. The anodic reaction resistance decreases while the cathodic reaction resistance increases, resulting in a small potential difference of only 10 mV between the anode and cathode. The resistance of the inner layer film decreases, while that of the outer layer film increases. SEM analysis shows that the surface becomes rougher with the addition of Ca²⁺, and 1-4 mm granular corrosion products are formed. This is due to the fact that Cu₄(OH)₆SO₄ has low solubility and forms a relatively dense passive film that inhibits the corrosion reaction. The added Ca²⁺ also reacts with SO₄^2- to form CaSO₄, which reduces the amount of Cu₄(OH)₆SO₄ generated at the interface, thus damaging the integrity of the passive film. Adding Ca²⁺ promotes the corrosion of copper by Cl^- and SO₄^2- and enhances the release of corrosion by-products, with the highest corrosion rate observed under the Cl^-/SO₄^2-/Ca²⁺ conditions. The resistance of the inner layer membrane decreases, while the mass transfer resistance of the outer layer membrane increases. Under the Cl^-/SO₄^2- conditions, the SEM surface of the Cu₂O particles is uniform in size, arranged in an orderly and compact manner. After adding Ca²⁺, the size of the particles becomes uneven, and the surface becomes rough and uneven. This is because Ca²⁺ firstly combines with SO₄^2-, thus promoting corrosion. And then the remaining Ca²⁺ combines with Cl^-, which inhibits corrosion. Despite the amount of remaining Ca²⁺ being small, it still promotes corrosion. The amount of released corrosion by-products is mainly controlled by the redeposition reaction that occurs in the outer layer membrane, determining the amount of Cu₂O to which the copper ions are converted. The increase in resistance of the outer layer membrane means that the charge transfer resistance of the redeposition reaction increases, and the reaction rate slows down. Consequently, the amount of Cu(ii) converted to Cu₂O decreases, leading to an increase in Cu(ii) in the solution. Therefore, adding Ca²⁺ in all three conditions results in an increase in the release of corrosion by-products.

Application of asymmetrical configuration in electrochemical noise to investigate corrosion inhibition of aluminum alloy by Ranunculus Arvensis/silver nanoparticles

Asymmetric Configuration (As-Co) in the electrochemical noise (EN) was used to evaluate Ranunculus Arvensis / silver nanoparticles (RA/Ag NPs) as corrosion inhibitor for aluminum alloy (AA 2030) when gets exposed to 3.5% NaCl media. The ECN results of Asymmetric Configuration (As-Co) and Symmetric Configuration (Sy-Co) were interpreted using wavelet and statistical methods. The standard deviation of partial signal (SDPS) plots derived using of wavelet. The SDPS plot of As-Co demonstrated that the quantity of electric charge (Q) decreased with the addition of the inhibitor up to the optimum amount (200 ppm) due to the decreased corrosion rate. Moreover, the use of As- Co leads to record signal of one electrode and prevent recording extra signals arising from two identical electrodes which confirmed by the statistical parameters. The As-Co made of Al alloys were more satisfactory for estimating inhibiting effect of RA/Ag NPs compared to Sy-Co. Besides, aqueous extract of Ranunculus Arvensis (RA) plant as reducing agent mediates the synthesis of silver nanoparticles (RA/Ag NPs). The prepared NPs have been elaborately characterized using Field-Emission Scanning Electron Microscopy (FESEM), X-Ray Diffraction (XRD) analysis, and Fourier-Transform Infrared Spectroscopy (FT-IR) that revealed suitable synthesize of the RA/Ag NPs.