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This paper aims to study the tribocorrosion and the surface repassivation behaviors of Monel 400 alloy in artificial seawater.

In this study, the tribocorrosion behavior of Monel 400 alloy was studied under different applied loads in artificial seawater by using a pin-on-disk tribometer equipped with an electrochemical workstation. The applied loads were selected ranging from 50 to 200 N. The surface repassivation behavior of Monel 400 alloy was studied by X-ray photoelectron spectroscopy.

It was demonstrated that mass loss was determined by the combined effect of mechanical wear and chemical corrosion. The surface repassivation mechanism of the alloy is that layer corrosion product film formed on the surface of Monel 400 alloy, which can protect metal matrix from future corrosion.

This research adds original content in revealing the tribocorrosion and surface repassivation behaviors of Monel 400 alloy under different loads, which offer a theoretical basis for the application under the corrosion and wear environment of Monel 400.

Introduction Although nickel is generally regarded as a corrosion resistant material its resistance to sea water is only moderate. In fast flowing sea water its corrosion rate is very low; of the order of 0.0005 in/yr. Under stagnant conditions, however, it is susceptible to pitting and crevice corrosion attack. Consequently, alloying has been a common method of improving corrosion resistance to obtain a material having the excellent resistance of nickel to fast flowing sea water together with an improved resistance to pitting corrosion.

The purpose of this study was to investigate the inhibitive action of some green leaves on Monel 400 alloy in acidic media.

Green leaves of Mespilus japonica, Ricinus communis L and Vitis vinifera were immersed in methanol solutions, separately, and filtrated after 48 h of immersion; the obtained filtrates were examined as corrosion inhibitors of Monel 400 alloy in hydrochloric acid solution (1.0M HCl). The performance of these inhibitors was evaluated using electrochemical impedance spectroscopy and potentiodynamic polarization. The effect of temperature on corrosion behavior of Monel 400 was also studied.

The results obtained showed that all tested inhibitors performed as good corrosion inhibitors. The inhibition process is attributed to the adsorption of the inhibitors on Monel surface. The adsorption behavior was found to follow Langmiur isotherm. The inhibition efficiencies of extracts increased with increasing the concentration of each inhibitor and deceased with increasing the temperature.

Practical implication These inhibitors could have application in industries where hydrochloric solutions were used to remove the surface impurities of Monel 400.

This paper helps to find new corrosion inhibitors that are safe and eco-friendly.

Electrochemical behaviour of inconel‐625 and monel‐400 alloys in 1M HC1 dissolved in H2O and methanol is the subject of the present investigation. Corrosion and electrochemical behaviour of metals and alloys in non‐aqueous solvents is of current interest, due to developments in the chemical and petrochemical industries; to solve problems arising with the use of alternative fuels and to study the failures of metallic materials in organic solvents.

When the engineers at the Thames Barrier control building decide the long‐awaited dangerous high tidal surge is imminent and start operations to close the barrier across the river, the gates must shut. There can be no question of component failures caused by corrosion from the river water. By then the trunnion shafts supporting the gates may have been immersed in the river for many years — a situation posing a corrosion hazard for items such as the stressed bolting fixing them to the support structures concreted into the piers.

The purpose of this paper is to study the susceptibility of these three commonly used corrosion resistance fasteners in seawater. For a more practical scenario, a local Atlantic coastal seawater as received was used.

Carbon fiber reinforced polymer (CFRP) was fabricated with T700 carbon fiber (Toray Inc.) and VE8084 vinyl ester resin (Ashland) to make a unidirectional composite panel of thickness 1.8 mm. A conductive paint was applied to one of the sample edges that was perpendicular to the fiber direction, providing an electrical contact with carbon fibers to connect a copper wire. This external electric connection was used for potential measurements of both the open circuit potential (OCP) of the CFRP sample, and the mixed potential of the fastened set: consisting of the CFRP and the metallic fastener fastened to it. Three common fastener alloys were selected: 316SS, Monel and Titanium. For this purpose, a high impedance voltmeter was used in conjunction with a saturated calomel reference electrode. Measurements were taken daily. For longer time measurements, a four-channel high impedance analog data logger was used with 30 min sampling rate.

For both 316SS and Monel fastened sets, crevice corrosion occurred inside the occluded regions of the set, when immersed in coastal seawater. The attack was more severe for 316 stainless steel set. An isolated island attack of faceted surfaces morphology was seen for 316SS set. While, a circular ring of preferential grain boundary attack appeared for Monel set, indicating an IR (voltage) drop mechanism is more likely operating. Titanium-fastened sets showed high resistance to crevice corrosion when simmered in seawater. However, for long-time exposure, the sets became more susceptible to crevice corrosion attack supported by CFRP attachment (oxygen reduction reaction taking place at the carbon fibers).

Evidently, titanium, stainless steels and Monel are good candidates for galvanic corrosion resistance. However, their susceptibility to crevice corrosion when coupled with CFRP is a new challenging topic that needs further investigation. This is very important today because the vast application witnessed for CFRP material. This work involves developing an original methodology for this kind of investigation and was done at advanced laboratories of SeaTech at Florida Atlantic University by the Atlantic coastline.

Background An increasing number of requests from the engineering industry are being received by the author's company to advise on procedures for modern anti‐corrosive treatment and protection of valves, pumps, compressors, heat exchangers, filters etc.

Nickel alloys are widely used as constructional materials in chemical processing industries. They are very resistant to pitting and crevice corrosion. In the present work, the corrosion behaviour of Monel in phosphoric acid of different concentrations has been studied by weight loss and electrochemical methods. It has been observed from the polarization studies that the passivation range slightly varies with H₃PO₄ concentration. The nature of the passive film has been investigated using the electrochemical impedance method.

The use of materials in marine environments has traditionally been associated with ships. However, in recent years, important new industries have grown up which present new material problems. Notable amongst such industries are offshore oil production and desalination (production of fresh water from seawater). Also, requirements for large amounts of cooling water by modern industry have often resulted in siting of plants by the ocean, particularly in arid areas such as the Middle East. This has increased interest in the use of materials for handling seawater.

SAFETY is uppermost in the minds of all who travel by sea, and the use of reliable materials and methods of boat construction is essential in establishing confidence. The use of fasteners which can perform their function without seizing or deterioration by corrosion over long periods of service goes a long way towards obtaining the desired standard of performance.