Corrosion Behavior In Seawater Research Articles

Corrosion resistance and mechanism of high‐entropy alloys: A review

AbstractEnvironmental corrosion inevitably occurs during the use of alloys, making their corrosion resistance a special requirement for their application under specific conditions. The environmental corrosion behavior of alloys, seawater corrosion behavior, corrosion resistance, and microstructure of high‐entropy alloys (HEAs) have been prominent research topics over the past decade, all of which warrant further investigation. The corrosion resistance and passivation film strength of HEAs could be enhanced by improving their microstructure with appropriate adjustments of their elemental composition and content. In this review, the research status and corrosion mechanism of HEAs in seawater solutions with NaCl as the main component were examined. Moreover, the correlation between the microstructure, elemental composition, and corrosion resistance of HEAs was revealed.

Effects of Lorentz Force and Gradient Force of Magnetic Field on the Seawater Corrosion Behavior of Carbon Steels

With the rapid development of modern civilization, the development of marine resources has become imminent, but seawater corrosion has become one of the most important factors hindering development. In order to overcome this problem, an environmentally friendly physical anticorrosion scheme based on a magnetic field () has been proposed. In this context, we investigate the effect of the Lorentz force and gradient force of a magnetic field on the corrosion behavior of carbon steel in seawater. The experimental results show that the gradient force of a magnetic field inhibits corrosion while the Lorentz force promotes corrosion. Especially in the (corrosion electrical field) case, the Lorentz force influence on the corrosion behavior is greater than the gradient force, while in case gradient force dominates. In addition, the effect mechanism of magnetic field on the corrosion behavior of carbon steel in seawater was revealed by comparison of corrosion product composition in different reaction regions and electrochemical impedance spectrum analysis, which will provide an experimental basis for the application of environmentally friendly marine anticorrosion technology based on a magnetic field.

Corrosion behavior of a newly developed high strength aluminum alloy with high magnesium content under simulated seawater environment

AbstractAMg61 (Al‐6.2% Mg), a novel form of high‐strength, high‐magnesium‐content aluminum alloy, has been developed for specific maritime engineering in recent years, while its corrosion behavior in seawater is still unknown. Therefore, the corrosion behavior of AMg61 in the simulated seawater was investigated herein, using a weight‐loss test and different electrochemical measurements. In addition, corrosion morphology and chemical contents were characterized by metallography, scanning electron microscopy, and energy‐dispersive spectroscopy. The results demonstrated that intergranular corrosion and microcracks developed first in the second phase of AMg61, followed by pitting corrosion. The matrix of AMg61, on the other hand, exhibited a uniform and exfoliation corrosion. The corrosion rate gradually decreased over time.

On the evolution of microstructure, texture and corrosion behavior of a hot-rolled and annealed AZ31 alloy

The microstructure and texture evolution of an AZ31 alloy were investigated after hot rolling and subsequent annealing using electron backscatter diffraction (EBSD). First, the alloy was hot-rolled at 350 °C up to low, medium and high strain (20, 50 and 85% of thickness reduction, respectively). The alloy samples where then annealed at 350 °C for 2, 10 and 60 min. The effect of strain level and annealing on corrosion behavior in seawater was also evaluated using electrochemical tests. At low strain, the microstructure was characterised by the absence of twinning, mainly due to the prior thermo-mechanical history of the as-received alloy. However, various modes of twinning were observed at medium strain. At high strain, the dynamic recrystallization process resulted in a microstructure with a typical basal texture. The results demonstrate that twins are responsible for the deviation of {0002} basal poles from normal towards the transversal direction. Annealing at 350 °C for up to 60 min led to normal grain growth in all the samples. In medium and highly strained samples, the deformation texture was retained, while the low strain sample underwent noticeable changes due to the absence of dynamic recrystallization. A synergetic effect of grain refinement and texture weakening was responsible for the alloy's enhanced corrosion resistance.

The effect of magnetic field pretreatment on the corrosion behavior of carbon steel in static seawater.

The corrosion behavior of carbon steel pretreated with a magnetic field before electrochemical testing was investigated in static seawater using electrochemical methods in the absence of an external magnetic field. The shift in corrosion potential was more significant with increasing pretreating magnetic field strength, and the corrosion current density also decreased. This implies that the carbon steel corrosion was inhibited. The main reason for this inhibition is that the magnetic field affects the formation of intermediate products on the carbon steel surface by both charge transfer and magnetic ion adsorption. The magnetic field pretreatment will likely offer a new approach for marine anti-corrosion technology.

Carbon network/aluminum composite made by powder metallurgy and its corrosion behavior in seawater

In this work, a carbon network/aluminum matrix composite material was made by the powder metallurgical approach. Pure aluminum powders with a diameter of less than 30 μm were compressed with sugar particles with the similar size under a pressure of 40 MPa. Sintering at 500 °C in pure argon gas for 2 h was performed to carbonize the sugar. After the sintered product was cooled down, microstructure analysis was carried out. It was found that high temperature sintering allowed the material to generate carbon networks distributed along the grain boundaries in the porous aluminum. An aluminum to sugar ratio of 1 to 1 reached the maximum carbon concentration in the composite for keeping the structural integrity. Characterization of the corrosion behaviors of the carbon network/porous aluminum composite material and a pure aluminum plate in seawater was conducted by measuring their Tafel plots. The Galvanic potential of the carbon network/porous aluminum composite material is about -0.62 V. The pure aluminum shows a more negative Galvanic potential of -0.755 V. As compared with pure aluminum, the composite material showed improvement on the corrosion property. The corrosion current of the composite in seawater is about 100 times lower than that of the pure aluminum. The existence of carbon network in the composite and the oxidized state of the sintered aluminum allows the composite material to be more corrosion resistant in seawater. For the materials processed with higher sugar content (with Al: sugar ratio of 1:1.25), carbon became the dominant phase in the composite. The material has a low strength and ease to get collapsed. The corrosion behavior of the composite made from low Al to sugar ratio raw material is similar to that of the one with Al: sugar ratio of 1:1. For the high carbon content composite material with Al: sugar ratio of 1:1.25, the Galvanic potential of the material is as high as -0.32 V, which is very close to the Galvanic potential of graphite in seawater. It shows the corrosion behavior of pure carbon in seawater.

Corrosion behavior in seawater of arc thermal sprayed Inconel 625 coatings with sealing treatment

In this study, zinc powder (Zinc), inorganic ceramic (Ceramic), and organic-inorganic composite ceramic (Hybrid) sealing processes were applied to improve the corrosion resistance of arc thermal sprayed Inconel 625 coatings. The Inconel 625 coating in seawater solution showed poor corrosion resistance due to its porosity and Cr depletion resulting from Cr oxide formation during the arc thermal spraying process. Zinc sealing formed a stable cathodic protection, but the local corrosion damage occurred largely in the anodic polarization experiment caused by an excessive dissolution reaction and a weak bonding force between the zinc particles. Hybrid sealing gave a better sealing effect, but surface corrosion damage appeared due to interconnected micro-crack defects on the surface. Ceramic sealing gave the best corrosion protection due to a high sealing efficiency and a lower surface damage tendency resulting from effectively blocked defects of the Inconel 625 coating.

New Composite Materials Based on Intermetallics for Protection Details of Hydropower Equipment from Cavitation, Hydroabrasive and Corrosion Wear

The corrosion behavior in seawater of NiAl and NiTi intermetallics and composites based on them has been studied in this paper. It was shown that the developed composite NiTi-30 wt.% CrB2 hardly corrodes. The developed materials are meant for protect different shipbuilding details and details of hydropower equipment from aggressive sea water environments, as well as against hydro-abrasive and cavitation wear.

A Study on the Corrosion Behavior in Sea Water of Welds Aluminum Alloy by Shielded Metal Arc Welding, Friction Stir Welding and Gas Tungsten Arc Welding

A Study on the Corrosion Behavior in Sea Water of Welds Aluminum Alloy by Shielded Metal Arc Welding, Friction Stir Welding and Gas Tungsten Arc Welding

Effect of Zinc Diffusion Distribution on Corrosion Behavior of Brazed Tube/Fin Assemblies of Aluminum Automotive Condensers

The aim of this research is the evaluation of corrosion behavior in Sea Water Acidified Accelerated Test (SWAAT) solution of tube/fin assemblies from two aluminum condenser prototypes with micro-channel tubes having similar compositions but different amount of sprayed zinc per unit area (5.5 and 4.2 g/m2, respectively). Such assemblies (Fig. 1) were brazed in a laboratory furnace under a pure nitrogen atmosphere. In order to simulate conditions for different diffusion rate and penetration depth, two sets of brazing parameters were selected: set A (610°C, 4min) and set B (600°C, 2min). The results of potentiodynamic polarization and electrochemical impedance measurements showed for both prototypes that the sample brazed under set B parameters exhibited lower corrosion rate compared to that brazed under set A parameters. The sample with lowest corrosion rate was the one with microchannel tubes containing 5.5 g/m2 of zinc before brazing. The observed corrosion behavior was correlated to zinc diffusion profiles obtained from SEM-EDS analysis. Galvanic current measurements showed that for short immersion times (1h) the tube is anodic to the fins, but the current is not stable and there is an evolution to lower values, suggesting that for long immersion periods there might be a inversion in the galvanic coupling. Figure 1

Effect of Radial Expansion of Cr-Mo Steel Tubes on Their Corrosion Behavior in Sea Water

This paper studies the effect of expansion ratio on the corrosion rate of the expanded tubes exposed to sea water as well as the microstructure changes caused by the expansion of Cr-Mo steel tubes to large permanent deformations. 2.25 Cr-1.0 Mo steel (schedule 40 and schedule 80) tubes were subjected to various expansion ratios of 10%, 15%, 20%, and 25% by pushing conical mandrels through them using a piston. The microstructure was also studied to determine the effect of the expansion on the grain structure of the material. Microscopic examination of the expanded tubes revealed that grains elongate along the direction of the hoop stress and this elongation increases with an increase of expansion ratio. Moreover, it was found that corrosion rate and hardness increase with an increase in expansion ratio.

The role of microstructure of nickel–aluminium–bronze alloy on its cavitation corrosion behavior in natural seawater

An investigation was carried out in our laboratory to study the effect of the microstructure of nickel–aluminum–bronze (NAB) alloy on its cavitation corrosion behaviour in seawater using a 20-kHz ultrasonic induced cavitation facility. Cavitation tests were made under free corrosion conditions as a function of exposure time in natural seawater. Optical and scanning electron microscopy showed NAB immersed in stagnant seawater suffered from selective corrosion of the copper-rich α phase at boundaries with intermetallic κ precipitates. The κ precipitates and precipitate-free zones did not suffer corrosion. Cavitation made the surface of this alloy very rough, with large cavities or pits, ductile tearing and corrosion of the boundaries of the α columnar grains. In addition, the number of cavities and their size increased with exposure time. Microcracks 5–10 μm long were observed in the α phase adjacent to κ precipitates along the cross-section of the material. Selective phase corrosion and cavitation stresses were considered to be the cause of the cracks observed.

The effect of duplex stainless steel microstructure on its cavitation morphology in seawater

An ultrasonically induced cavitation facility was used to study the effect of a cast duplex stainless steel (DSS) microstructure on its corrosion behavior in seawater. Under cavitation conditions, small cavities initiated in the ferritic matrix and at the ferrite–austenite boundaries. With the progress of cavitation, the attack concentrated in the austenitic phase and then spread to the ferritic phase and was associated with cleavage-like facets, ductile tearing, river patterns and crystallographic steps at later stages. Cross-sections of specimens revealed microcracks initiating from the ferritic matrix at the bottom of cavities. Crack propagation into the matrix was impeded by the austenitic islands.

Seawater corrosion behavior of laser surface modified Inconel 625 alloy

Seawater corrosion behavior of laser surface processed Inconel 625 alloy was investigated. Three laser surface modified samples were prepared, one by laser melting, and the other two by laser melt/particle injection processing with tungsten carbide (WC) and titanium carbide (TiC) particles, respectively. Particle injection involved embedding the carbide particles into a laser melted surface and resulted in a metal matrix-particulate composite surface layer which was both hard and wear-resistant. While Inconel 625 is a corrosion resistant alloy suitable for marine applications, and WC and TiC are generally inert to chemical attack, results from this study showed that laser surface modification produced microstructures that were susceptible to seawater corrosion to varying degrees. Nominal corrosion was observed in the dendritic structure produced by laser melting of the alloy surface. In the particle injected samples, the WC particulate phase in contact with the Inconel alloy matrix showed different kinds of attack, while the TiC particulate phase showed none. In both particle injected samples, resolidification of the Inconel alloy melt produced significant departures in composition and microstructure from those of the base alloy. Eutectic and dendritic carbides and, in WC, interphase carbides were some of the resolidification byproducts that formed in the matrix surrounding the particulate. Alloyed with solute elements from the base alloy, each product phase contributed to unique forms of corrosion. A qualitative analysis of the corrosion behavior of the injected samples showed that corrosive damage was more severe in the WC injected sample than in the TiC injected sample and in the laser melted sample. This paper describes the processing, microstructural and compositional characterization, and seawater corrosion behavior of the laser surface modified samples, and attempts to explain the observations as a consequence of the formation of galvanic cells.