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The pipeline system in the oil and gas industry is the heart for transportation of crude and refined petroleum. Nevertheless, continuous exposure of the pipeline surfaces to impurities and sources of corrosion such as sulfur and chromate is totally unavoidable. Vast employment of commercial corrosion inhibitors to minimize the corrosion is being restrained due to toxicity towards the environment. The emergence of “green” chemistry has led to the use of plant extracts and fruit wastes which have proven to be good corrosion inhibitors. This paper aims to provide insight into carrying out further investigation under this research theme for accurate inhibition efficiency measurement.

Titanium (Ti) and its alloys possess high biocompatibility and corrosion resistance due to Ti ability to form a passive oxide film, i.e. TiO2, immediately after contact with oxygen. This passive layer is considered stable during function in the oral cavity, however, emerging information associate inflammatory peri-implantitis to vast increases in Ti corrosion products around diseased implants as compared to healthy ones. Thus, it is imperative to identify which factors in the peri-implant micro-environment may reduce Ti corrosion resistance. The aim of this work is to simulate peri-implant inflammatory conditions in vitro to determine which factors affect corrosion susceptibility of Ti-6Al-4V dental implants. The effects of hydrogen peroxide (surrogate for reactive oxygen species, ROS, found during inflammation), albumin (a protein typical of physiological fluids), deaeration (to simulate reduced pO2 conditions during inflammation), in an acidic environment (pH 3), which is typical of inflammation condition, were investigated. Corrosion resistance of Ti-6Al-4V clinically-relevant acid etched surfaces was investigated by electrochemical techniques: Open Circuit Potential; Electrochemical Impedance Spectroscopy; and Anodic Polarization. Electrochemical tests confirmed that most aggressive conditions to the Ti-6Al-4V alloy were those typical of occluded cells, i.e. oxidizing conditions (H2O2), in the presence of protein and deaeration of the physiological medium. Our results provide evidence that titanium's corrosion resistance can be reduced by intense inflammatory conditions. This observation indicates that the micro-environment to which the implant is exposed during peri-implant inflammation is highly aggressive and may lead to TiO2 passive layer attack. Further investigation of the effect of these aggressive conditions on titanium dissolution is warranted.

The adsorption mechanism and inhibitive action of the Eucalyptus plant leaf extract (Eu) on the corrosion of mild steel in 0.5 M H 2 SO 4 and 0.5 M H 3 PO 4 solutions were investigated by potentiodynamic polarization curves measurements and electrochemical impedance spectroscopy technique. Potentiodynamic polarization curves revealed that the Eucalyptus leaf extract acts as a mixed type inhibitor in both acidic solutions. The impedance responses indicated that the corrosion process occurs under activation control. Fourier transform infrared spectroscopy has been used to predict the possible major chemical constituent of the leaf extract. Four adsorption isotherms including Langmuir, kinetic–thermodynamic, Flory–Huggins and Temkin model were used to investigate the mode of inhibition of Eucalyptus leaf extract. The free energy of adsorption showed that the corrosion inhibition takes place by spontaneous physical adsorption of Eucalyptus leaf extract molecules on the mild steel surface. The obtained data indicated that Eucalyptus leaf extract is a more efficient inhibitor of mild steel corrosion in 0.5 M H 2 SO 4 than in 0.5 M H 3 PO 4 solutions. Thermodynamics activation parameters were also calculated and discussed.

Self-healing coating based on nanocontainers (NCs) has been emerging as a great strategy to improve the anticorrosion ability of susceptible metal substrate. However, all the research referred to such smart coating to date is focus on organic coating instead of metallic coating. To fill this gap, 2-mercaptobenzothiazole (MBT) loaded porous hollow SiO 2 NCs are synthesized and incorporated successfully into an electroless Ni coating on Mg alloy in this work. The surface morphologies and the loading properties of the NCs are characterized by scanning electron microscopy, transmission electron microscopy, ultraviolet–visible spectrophotometer, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The favorable performance of Ni coating after incorporation of NCs is demonstrated by potentiodynamic polarization (PDP), linear polarization, and electrochemical impedance spectroscopy. Based on the results of PDP test, the corrosion current density ( i c ) of the MBT@NCs (MNCs)-engineered Ni coating reduces slightly from 6.4 to 5.4 μA cm −2 after immersion in a corrosive media, while the value for MNCs-free coating increases by almost a factor of ten from 6.8 to 67.4 μA cm −2 . Our findings demonstrate the possibility of using corrosion inhibitors loaded NCs to enhance the corrosion resistance of a metallic coating and give new perspectives for functionalization of a metallic coating with nanomaterials.

Microbial colonization can be detrimental to the integrity of metal surfaces and lead to microbiologically influenced corrosion (MIC). Biocorrosion is a serious problem for aquatic and marine industries in the world. In Minnesota (USA), where this study was conducted, biocorrosion severely affects the maritime transportation industry. The anticorrosion activity of a variety of compounds, including chemical (magnesium peroxide) and biological (surfactin, capsaicin, and gramicidin) molecules were investigated as coating additives. We also evaluated a previously engineered, extremely stable, non-biocidal enzyme known to interfere in bacterial signaling, SsoPox (a quorum quenching lactonase). Experimental steel coupons were submerged in water from the Duluth Superior Harbor (DSH) for 8 weeks in the laboratory. Biocorrosion was evaluated by counting the number and the coverage of corrosion tubercles on coupons and also by ESEM imaging of the coupon surface. Three experimental coating additives significantly reduced the formation of corrosion tubercles: surfactin, magnesium peroxide and the quorum quenching lactonase by 31%, 36% and 50%, respectively. DNA sequence analysis of the V4 region of the bacterial 16S rRNA gene revealed that these decreases in corrosion were associated with significant changes in the composition of bacterial communities on the steel surfaces. These results demonstrate the potential of highly stable quorum quenching lactonases to provide a reliable, cost-effective method to treat steel structures and prevent biocorrosion.

It is well established that magnesium has a considerable potential for use as a biodegradable material. This report describes the effect of processing by severe plastic deformation (SPD) on the grain refinement, mechanical behavior, biocompatibility and corrosion behavior of commercial purity magnesium. The material was received as cast slabs and processed by rolling, equal-channel angular pressing and high-pressure torsion to produce samples with average grain sizes in the range of ~0.5–300 μm. The results show that severe plastic deformation does not affect the biocompatibility. However, the corrosion behavior is affected by the processing route. Specifically, SPD processing leads to general corrosion as opposed to localized corrosion in the as-cast and hot-rolled condition.

ABSTRACT Sporomusa sphaeroides related strains are to date the only homoacetogens known to increase metallic iron corrosion. The goal of this work was to isolate additional homoacetogenic bacteria capable of using Fe(0) as electron donor and to explore their extracellular electron transfer mechanism. Enrichments were started from anoxic corrosion products and yielded Acetobacterium as main homoacetogenic genus. Isolations were performed with a new procedure using plates with a Fe(0) powder top layer. An Acetobacterium strain, closely related to A. malicum and A. wieringae, was isolated, in addition to a S. sphaeroides strain. The Acetobacterium isolate significantly increased Fe(0) corrosion ((1.44 ± 0.16)-fold) compared to abiotic controls. The increase of corrosion by type strains ranged from (1.28 ± 0.13)-fold for A. woodii to (2.03 ± 0.22)-fold for S. sphaeroides. Hydrogen mediated the electron uptake from Fe(0) by the acetogenic isolates and tested type strains. Exchange of the medium and SEM imaging suggested that cells were attached to Fe(0). The corrosion enhancement mechanism is for all tested strains likely related to free extracellular components catalyzing hydrogen formation on the Fe(0) surface, or to the maintenance of low hydrogen concentrations on the Fe(0) surface by attached cells thereby thermodynamically favoring hydrogen formation. Sporomusa and Acetobacterium strains isolated with metallic iron as electron donor enhance Fe(0) corrosion

The present report describes phase formation, magnetic and corrosion behavior of the AlCrFeMnNiTi high entropy alloy (HEA) synthesized through mechanical alloying. Simple solid solution of FCC and BCC phases are evolved after 25 h of MA. DSC analysis confirms that the synthesized phases of AlCrFeMnNiTi HEA are stable up to 550 °C and a re-crystallization is occurred at temperature greater than 550 °C. In order to investigate the effect of annealing on phase formation and magnetic characteristics, the synthesized HEA was annealed at 700 °C for 1 h and found that the volume fraction of BCC phase decreased. The synthesized HEA shows better ferromagnetic behavior with Ms = 17.55 emu/g and Hc = 153.8 Oe as compared to some of the recently reported HEAs and previously reported CrFeMnNiTi HEA by us. Moreover, corrosion behavior of the annealed AlCrFeMnNiTi high entropy alloy in 0.5 M and 1 M NaCl solution is also investigated. It is found that the annealed HEA shows good corrosion resistance in 0.5 M NaCl solution due to the presence of Al.

Incorporation of nanofillers into the organic coatings might enhance their barrier performance, by decreasing the porosity and zigzagging the diffusion path for deleterious species. Thus, the coatings containing nanofillers are expected to have significant barrier properties for corrosion protection and reduce the trend for the coating to blister or delaminate. On the other hand, high hardness could be obtained for metallic coatings by producing the hard nanocrystalline phases within a metallic matrix. This article presents a review on recent development of nanocomposite coatings, providing an overview of nanocomposite coatings in various aspects dealing with the classification, preparative method, the nanocomposite coating properties, and characterization methods. It covers potential applications in areas such as the anticorrosion, antiwear, superhydrophobic area, self-cleaning, antifouling/antibacterial area, and electronics. Finally, conclusion and future trends will be also reported.

In this work, the aqueous Lawsonia inermis extract (LI) is investigated as an economic and green deterioration inhibitive formula for steel alloy 4130 in 3.5 wt.% NaCl solutions. The water-based extraction process is considered as one of the cheapest techniques for preparation of active ingredients of natural products. These ingredients play an important role in corrosion mitigation of steel alloy 4130 in saline media. This extract was subjected to three different parameters: inhibitor concentration, rotation speed, and temperature in 3.5 wt.% NaCl solutions. The electrochemical techniques are used to perceive the corrosion behavior, and the obtained results were dedicated to theoretical explorations to assess the features of corrosion inhibition and the adsorption over the steel substrate in 3.5 wt.% NaCl solutions. Affording to the electrochemical techniques of LI showed very promising results against corrosion depending on the inhibitor concentrations. The inhibition efficiency of LI was additionally appraised at three diverse temperatures, and the results disclosed that the inhibition efficiency is decreased. Additionally, the theoretical aspects illuminated that the main active ingredients of LI have a proclivity to coagulate on the steel substrates allowing these areas to paradigm a protecting layer on the steel surfaces. This behavior is in provision of investigational results. Statistical studies were used to examine the consequence of chief constraints (i.e., inhibitor concentration, temperature, and rotation speed) on the inhibition efficiency and the rate of corrosion of steel alloy 4130. The inhibitive effect of LI in contradiction of the corrosion of steel alloy 4130 surfaces is considered by resources of DFT/6-31G(d) calculations. The quantum chemical parameters interrelated to the inhibition efficiency are considered.