Band 40, Heft 4

The use of magnesium and its alloys as temporary implants has gained interest in the last two decades due to their good mechanical properties and bio-degradability in the in-vivo conditions. However, the issues of higher corrosion rate and stress corrosion cracking persist, which are responsible for the implants’ early failure. This review paper focuses on the challenges involved in the use of magnesium-based implants and the advancements in mitigating the corrosion-related issues for in-vivo use of biodegradable magnesium alloy implants. Herein we review the degradation behavior of three groups of magnesium alloys, i.e., aluminum-containing Mg alloy, rare earth element (REE) containing Mg alloy, and aluminum-free Mg alloy in a variety of testing media. We also review various surface modification techniques such as mechanical methods, physical methods, and chemical methods adopted to address the shortcomings of the Mg alloys. Furthermore, recent developments in Mg based bioimplants such as Mg-based open porous scaffolds, nanostructured Mg alloys and Mg based bulk metallic glasses are reviewed. In the end, recent clinical trials of the Mg-based implant were reported in detail.

The present paper is aimed to review the efficiency of eco-friendly, natural and cheap bio-waste materials as corrosion inhibitors on metal surfaces in different corrosive media. Various bio-waste materials are the best substitutes for the synthetic organic, inorganic and polymeric inhibitors. Most of the bio-waste material adsorbed on the metal surface in aqueous medium followed the Langmuir adsorption isotherm. The presence of organic constituents in bio-waste materials is responsible for the protection of metals in aggressive medium. The effectiveness of these bio-waste materials to inhibit metal corrosion is well studied by non-electrochemical methods like weight loss and atomic absorption spectroscopy techniques as well as electrochemical methods like polarization and impedance measurements. Surface studies were studied through SEM, EDS, XRD, AFM and XPS techniques. Computational studies using DFT and MDS were also reported.

A phase field (PF) based electrochemical model is presented for simulation of galvanic corrosion. Distributions of electrolyte potential and current density on anode and cathode surfaces are obtained by coupling the PF variable with electrochemistry. Evolution of surface recession is naturally obtained by solving the PF equations without tracking the evolving boundary. Numerical implementation involves solving the governing equations on a fixed mesh. The sharp interface as the limit of the PF model is shown by an asymptotic analysis. Two benchmark problems are discussed: a magnesium alloy–mild steel couple exposed to 5% NaCl solution and crevice corrosion for nickel in 1 N sulfuric acid. A comparison is made considering available experimental data as well as other simulation data by an arbitrary Lagrangian–Eulerian method. Good agreement is obtained.

The purpose of the present work is to investigate the corrosion sensitivity of pipelines of oil and gas wells under complex environmental conditions (i.e., the primary and secondary relationship of the influence of different environmental factors on pipeline corrosion). The orthogonal experiment is introduced to design the experimental scheme. The weight loss method is employed to analyze the average corrosion rate of N80 steel under different environmental conditions. And then the scanning electron microscope is used to explore the surface and cross-section corrosion morphology of the corrosion products. Besides, the components of corrosion products are obtained by the energy spectrum analysis. The research results indicate that H 2 S partial pressure is the most sensitive factor to the corrosion of N80 pipeline and the influence of CO 2 partial pressure on corrosion of N80 pipeline is weaker than Cl − concentration and temperature in the South China Sea. The study can help the oil drilling engineering search for direct and effective corrosion inhibitors under complex environmental conditions.

The corrosion characteristics of newly synthesized (ATOMET 4601 + 2%TiC) high strength alloy steels through powder metallurgy (P/M) technique has been under taken in the present research work. The green compacts of 0.5 aspect ratio (h/d) were sintered at 1100 ± 10 °C for 30 min in nitrogen purged electric muffle furnace. The sintered compacts were cold forged to obtain various densities of alloy steels preforms. Electrochemical and aqueous immersion corrosion tests were carried out on the cold forged alloy steels using pickling acid medium at various time periods. The experimental results show that the addition of TiC to the ATOMET 4601 decreases the corrosion rate of alloy steel and the corrosion rate is found to decrease with increase in density in the alloy steel compositions. Surface morphology, SEM, and XRD were also corroborated with the corrosion characteristics of the P/M alloy steels.

Stainless steel is known for its superior corrosion resistance in industrial applications. In this work, corrosion modeling of stainless steel 316L is presented using artificial neural networks. The experimental setup consists of a loop containing stainless steel elbow with simulated seawater of known concentration continuously flowing at a specific flow rate, thus allowing to study the effect of flow dynamics and salt concentration on corrosion. Electric field mapping setup is used to collect the voltage and current information along with the temperature of the elbow section. In addition to modeling, characteristics of the observed scale deposits are also studied in-depth and briefly reported in this work.