Natural Corrosion Inhibition and Adsorption Characteristics of Tribulus terrestris Plant Extract on Aluminium in Hydrochloric Acid Environment

Corrosion inhibitive and adsorption capabilities of Tribulus terrestris plant extract on aluminum in 1.0 N HCl solution was evaluated by mass loss and electrochemical methods. The inhibition efficiency increased with increasing extract concentration, whereas it decreased with increasing immersion time. The adsorption of the extract on the metal surface was physisorption, supported by ΔGads values( around -20 kJ mol−1) and obeyed by Langmuir, Temkin and Freundlich adsorption isotherms. Electrochemical studies revealed mechanistic aspects of corrosion inhibition like Potentiodynamic polarization measurements indicated the nature of inhibitor is a mixed type and impedance studies supported the formation of a protective layer of inhibitor on a metal surface. SEM micrograms were also applied to study surface morphology. These images confirmed the creation of a protective film over the metal surface.

OAT EXTRACT AS A NATURAL CORROSION INHIBITOR FOR MILD STEEL IN 3% NaCl SOLUTION

In this work, we have tested a new inhibitor formulation that is effective, economically efficient and in accordance with environmental legislation. The inhibitor tested is the crude extract of the oat plant (denoted as OE) obtained by the reflux method in the water. This extract is then used as a corrosion inhibitor of mild steel in 3% NaCl. This study was carried out by using electrochemical polarizations, Electrochemical Impedance Spectroscopy and gravimetric techniques. The results obtained showed that this extract satisfactorily inhibits the dissolution rate of mild steel. The inhibition efficiency increases with inhibitor concentration and reaches 72% at 5[Formula: see text]g[Formula: see text][Formula: see text][Formula: see text]L[Formula: see text] of oat extract. Polarization data indicate that the extract acted as mixed type. The adsorption of the inhibitor on the mild steel surface in 3% NaCl follows the Langmuir adsorption isotherm. SEM analysis of the electrode surface condition confirms the results obtained.

Innovative Method for Coating of Natural Corrosion Inhibitor Based on Artemisia vulgaris

In this work, the production of a novel methodology for the application of natural corrosion inhibitors on steel, using an autoclave is presented. Tests were carried out using Artemisia vulgaris. The inhibitor was produced with a simple soxhlet extraction process using 15 g of Artemisia vulgaris and 260 mL of Ether. Once the inhibitor was produced, the steel was immersed in it, to form a coating that protects the material against corrosion. Thermogravimetry analyzes (TGA) were performed on the inhibitor, to determine the degradation temperature; it was observed that, at 321 °C, the loss of organic mass begins. After applying the inhibitor to the steel, the Fourier Transform Infrared Spectroscopy (FTIR) technique was used to determine the vibrational bands and the difference between the spectra for the steels before and after the coating was applied. For the evaluation of the method efficiency, Electrochemical Impedance Spectroscopy (EIS) and polarization resistance tests were performed, where Nyquist diagrams and Tafel curves were obtained, for steels with and without treatment. In this case, an increase of 93% in the corrosion resistance, and an 88% decrease in the corrosion rate were observed, proving that this methodology can be used to protect steel against corrosion and extend the steel’s useful life.

Effect of test methods on corrosion phenomena of steel in highly resistive concrete systems and data interpretations

Fly ash and limestone calcined clay cement (LC3) are being used/introduced in concrete to enhance chloride resistance. In this study, sixty specimens (with steel in three concrete systems, namely OPC, fly ash, and LC3 with surface resistivity of ≈10, ≈25, and ≈200 kΩ.cm, respectively) were subjected to impressed corrosion and the results were compared with 15 lollipop steel-mortar specimens subjected to natural corrosion under wet-dry/chloride conditions. It was found that the traditional way of impressed corrosion tests can induce microstructural changes in highly resistive concrete cover and at steel-concrete interface; hence, are not suitable for evaluating corrosion resistance (say, corrosion rate and corrosion-induced cracking) in highly resistive concrete systems. Further, the Raman spectra from the corroded steel surfaces indicated that the impressed corrosion and natural corrosion tests led to different forms of corrosion (i.e., uniform and pitting, respectively) and different compositions of corrosion products (i.e., ‑Fe2O3 and FeOOH phases). This led to different expansive stresses making the lab-to-field correlations inappropriate in case of highly resistive concrete systems. This paper recommends natural corrosion tests exposed to wet-dry conditions and not the impressed corrosion tests for assessing corrosion phenomena of steel in highly resistive concrete systems.

Time Scale of Chloride-Induced Corrosion on Circular Section RC Linked Accelerated Test to Natural Corrosion

The time scale in accelerated decay is essential for studying the durability of reinforced concrete (RC) structures exposed to the chloride corrosion environment. An accelerated corrosion test (ACT) was carried out on RC specimens were conducted under different chloride concentrations and applied voltages, with the information of steel measured. A novel prediction model of the complete corrosion process is proposed to evaluate the time correlation between accelerated decay and natural corrosion. The corrosion process of RC is divided into two stages: corrosion initial stage and corrosion stage of reinforcement. For the first stage, the coefficient of circular section members is presented. For the second stage, the accelerated factor of the test for the natural environment is proposed based on the Arrhenius-type and Faraday’s law. It is calculated by making regressions among some values of parameters, while moving to natural corrosion are extrapolating. The accelerating effect of applied voltages increases in the low-chloride environment, which is better than that in the high-chloride environment. This study provides calibration of the time scale for laboratory tests to analyze the performance of RC structures after corrosion.

Toward Tailoring the Degradation Rate of Magnesium-Based Biomaterials for Various Medical Applications: Assessing Corrosion, Cytocompatibility and Immunological Effects

Magnesium (Mg)-based biomaterials hold considerable promise for applications in regenerative medicine. However, the degradation of Mg needs to be reduced to control toxicity caused by its rapid natural corrosion. In the process of developing new Mg alloys with various surface modifications, an efficient assessment of the relevant properties is essential. In the present study, a WE43 Mg alloy with a plasma electrolytic oxidation (PEO)-generated surface was investigated. Surface microstructure, hydrogen gas evolution in immersion tests and cytocompatibility were assessed. In addition, a novel in vitro immunological test using primary human lymphocytes was introduced. On PEO-treated WE43, a larger number of pores and microcracks, as well as increased roughness, were observed compared to untreated WE43. Hydrogen gas evolution after two weeks was reduced by 40.7% through PEO treatment, indicating a significantly reduced corrosion rate. In contrast to untreated WE43, PEO-treated WE43 exhibited excellent cytocompatibility. After incubation for three days, untreated WE43 killed over 90% of lymphocytes while more than 80% of the cells were still vital after incubation with the PEO-treated WE43. PEO-treated WE43 slightly stimulated the activation, proliferation and toxin (perforin and granzyme B) expression of CD8+ T cells. This study demonstrates that the combined assessment of corrosion, cytocompatibility and immunological effects on primary human lymphocytes provide a comprehensive and effective procedure for characterizing Mg variants with tailorable degradation and other features. PEO-treated WE43 is a promising candidate for further development as a degradable biomaterial.

Failure Analysis of the Strain Clamp Steel Anchor Corrosion of a 500 kV Transmission Line

By macroscopic observation, composition analysis, mechanical properties test, SEM, energy spectrum, overall grip tensile test and finite element mechanics calculation method, the strain clamp steel anchor corrosion failure of a 500 kV transmission line is analysed. The results show that the corrosion of steel anchor for 31 years are the result of the natural corrosion, steel anchor corrosion rate is accelerated due to the galvanic corrosion, crevice corrosion, stress and damaged surface of the galvanized layer, and achieve C4 environment (zinc 2.1–4.2 um per year, carbon steel 50–80 um per year). The hardware are qualified. It is suggested to replace the steel anchor with yellow rust on the surface after 5 years, and to reevaluate the next maintenance cycle of the gold fittings without yellow rust on the surface at present, and replace it when the corrosion depth reaches 10%. Before replacement, all fittings should be monitored, especially steel anchor.

Analysis of Two Bronze Mirrors With Tin-rich Surface

"black lacquer " and “silver lacquer”are very special categories of ancient chinese bronze mirrors, and the cause of the formation of lacquer surface has attracted much attention. In this paper, metallographic microscope, scanning electron microscope are used to analyze one "black lacquer " and one “silver lacquer”bronze mirror. The matrix of the two mirrors is copper-tin alloy with lead and the metallographic structure is as cast. The tin-rich layer with uneven thickness exists on the surface of the 2 mirrors. Based on the analysis of tin-rich layer, it is concluded that the“silver lacquer” is intentionally artificial, and its surface is treated with lead-tin amalgam, which is composed of mechanical combination and micro-metallurgy. The "black paint" was formed by natural corrosion in the underground environment.