Alloys In Seawater Research Articles

Al-4.5%Mg-0.6%Mn 알루미늄 합금의 정전위 시간 변수에 따른 손상거동 평가

In general, aluminum alloys forms the passive film(, ) in neutral solution. However, the passive film created on the surface will be destroyed by chloride ions contained in sea water so the corrosion will occur. In this study, in order to solve the problem of corrosion under a seawater environment, potentiostatic protection techniques were applied to Al-4.5%Mg-0.6%Mn aluminum alloy in seawater. At polarization experiments, active state were observed at anodic polarization and concentration polarization by reduction of dissolves oxygen and activation polarization were found at anodic polarization. As a results of potentiostatic experiment, calcareous deposit were created much more as applying time increase from the turning point of the concentration polarization and activation polarization and crevice corrosion was partially observed between calcareous deposit and surface of base metal. Overall potentiostatic anodic polarization experiment was difficult to apply potentiostatic corrosion protection technology by occurrence of active state, whereas potentiostatic cathodic polarization experiment examined optimum corrosion protection condition of -1.1 V~-0.75 V within the range of concentration polarization considered various applying time.

Electrochemical characteristics of Al–Mg and Al–Mg–Si alloy in sea water

Among Al alloys, particularly 5000 series Al–Mg and 6000 series Al–Mg–Si often used as marine materials have excellent corrosion resistance, low melting point, and thereby showing recycling availability when compared to other metals. Variety experiments were conducted to select the most suitable material for marine environments. All electrochemical experiments were conducted in natural seawater. The corrosion test was performed in many methods such as anodic/cathodic polarization and Tafel analysis using multi-channel potentio/galvanostat WMPG–1000. As results, anodic and cathodic polarization behaviors indicate the characteristics of passive state and concentration polarization by reduction reaction in dissolved oxygen, which shows excellent electrochemical behaviors. Tafel analysis results show no significant difference but 5052-O alloy of various alloy materials indicates the lowest corrosion current density. Therefore, 5052-O Al alloy presents most anti-corrosion material in marine environment.

Study of Henna (Lawsonia inermis) as Natural Corrosion Inhibitor for Aluminum Alloy in Seawater

Commercial henna (Lawsonia inermis) was investigated to inhibit the corrosion of aluminum alloy through immersion in seawater. The aluminum alloy (5083) was prepared in size of 25mm × 25mm × 3mm. The immersion test was conducted in seawater with different concentration of henna, 100ppm, 300ppm, 500ppm for duration of 60 days. Four characterizations were performed in this study which was weight loss study, Fourier Transform Infrared (FTIR), Electrochemical Impedance Spectroscopy (EIS) and adsorption isotherm. The results indicated that henna has major constituents of lawsone which contributed to the chemisorptions or adsorption process by forming an isolation layers on the aluminum alloy surface which follows the Langmuir adsorption isotherm. It was found that the protection layer attached on metal was not permanent and precipitation occurred as the time increases. The highest inhibition efficiency was found at 88% (500ppm). This research found that henna is an excellent natural inhibitor for aluminum alloy in seawater.

Chemical equilibriums in the aqueous solutions-aluminum-magnesium alloys system. The nature of corrosion stability of alloys

The nature of stability of aluminum-magnesium materials in aqueous media has been discovered by using the Auger and atomic absorption spectroscopy. It was established that the composition of protective film formed on the aluminum-magnesium alloy in sea water, along with aluminum and oxygen, included also calcium, magnesium, and carbon. Under the scale-free conditions aluminum was not practically detected in external layers of the film consisting of oxides of calcium and magnesium compounds. Magnesium generally passes into solution during the corrosion process, while aluminum remains in the oxide film. The thickness of protective film was also measured. Data obtained during the spectral studies were in good agreement with the results of electrochemical measurements under the same conditions.

Discharge behavior of Mg–4 wt%Ga–2 wt%Hg alloy as anode for seawater activated battery

Magnesium–gallium–mercury alloy is one of the new developed anode materials for seawater activated batteries. The potentiodynamic polarization, galvanostatic discharge and electrochemical impedance spectroscopy of Mg–4%Ga–2%Hg alloy in seawater are studied and compared with commercial AZ31 and AP65 alloys in this study. The results show that Mg–4%Ga–2%Hg alloy exhibits different discharge behaviors in as-cast, homogenizing, rolling and annealing conditions. The annealing Mg–4%Ga–2%Hg sheet obtains the most negative corrosion potentials in different current densities. And the Mg–4%Ga–2%Hg alloy provides more negative corrosion potentials than AZ31 and AP65 alloys. EIS studies reveal that the Mg–Ga–Hg alloy/seawater interfacial process is determined by an activation-controlled reaction. The Mg 3Hg and Mg 21Ga 5Hg 3 phases improve the electrochemical properties of Mg–4%Ga–2%Hg alloy. The assembled prototype battery with Mg–4%Ga–2%Hg alloy as anode and CuCl as cathodes exhibits a satisfactory discharge performance because of the advantages in discharge characterizations and microstructure of the Mg–4%Ga–2%Hg alloy.

Experimental and density functional studies on the corrosion behavior of the copper-nickel-tin alloy

The corrosion behavior of copper-nickel-tin alloy in seawater with and without SRB has been tested by electrochemical techniques, SEM micrographs and EDX spectra. The geometric and electronic structure and active sites of Cun, Cun−1Ni and Cun−1Sn (n⩽9) clusters have been studied using DFT. The results indicated nickel and tin preferred to be the surface or outer layer in copper alloy, formed an oxide film on surface, then alloy would be corroded to Cu2O mostly after immersion. The corrosion process was accelerated in the presence of SRB, the mainly corrosion product was Cu2S, which was less protective for alloy.

SEM-EDS characterization of natural products on corrosion inhibition of Al-Mg-Si alloy

The corrosion resistance of aluminum and its alloys is the subject of tremendous technological importance due to their increased industrial applications. The corrosion protections and the mechanism of corrosion inhibitions of natural products for an Al-Mg-Si alloy in seawater were investigated at room temperature. The surface morphology was studied by means of macro scale electrochemical techniques and localized microscopic methods, i.e., Scanning electron microscope (SEM) with associated elemental analysis by energy dispersive spectrometer (EDS). SEM examinations provided morphological characterization of the surface of Al-Mg-Si alloy sample before and after immersion in seawater; meanwhile surface analytical techniques by the EDS allowed us to investigate detail the chemical composition of aluminum oxide layers. The experiments were performed with Al-Mg-Si alloy, immersed in a 5 L beaker containing seawater with and without the natural products for 60 days at room temperature. The SEM results indicate that the natural products (natural honey, vanillin, and tapioca starch) absolutely inhibited the corrosion products on the specimen surfaces. They also protected the passive film from dissolution in seawater. The EDS spectrums were determined that carbonaceous, carbonyl, methoxy and hydroxyl groups as functional groups of natural products in inhibition mechanism.

The effects of temperature, dissolved oxygen and the velocity of seawater, on the corrosion behavior of condenser alloys

PurposeThe purpose of this paper is to study the effects of temperature, dissolved oxygen (DO) and velocity of seawater on corrosion behavior of three copper‐based alloys (admiralty brass, aluminum brass and Cu‐5Ni alloy used in condenser tubes).Design/methodology/approachA series of electrochemical tests were carried out in seawater at different temperatures and DO contents using both stationary and rotating‐disc electrodes in order to investigate the corrosion behavior of alloys under these conditions.FindingsIt was found that admiralty brass exhibited a significantly higher corrosion rate and Cu‐5Ni alloy was more resistant to corrosion than were the brasses. With increasing temperature, the corrosion rates of the brasses increased. Selective zinc dissolution took place over the whole temperature range. Increasing temperature decreased the corrosion rate of Cu‐5Ni alloy in seawater due to formation of a passive film. The passivation of the alloy could be explained by the presence of greater proportion of nickel at the metal surface. Brasses, especially admiralty brass, exhibited higher corrosion rates in high concentrations of DO, whereas the Cu‐5Ni alloy was virtually immune to corrosion under such conditions. Increasing the water velocity increased the corrosion rate of admiralty brass but velocity had no effect on the corrosion rate of aluminum brass and Cu‐Ni alloy.Originality/valueThis paper provides information about corrosion behavior of three copper alloys used for common condenser tubes. The study fulfilled the objective of the investigation and contributes to research on corrosion behaviors of copper alloys in seawater.

Preliminary Study of the Influence of Machining Conditions in the Response to Corrosion of UNS-A92024 Alloy

In the aeronautical industrial sector, the control of the manufacturing process allows to fit the results to the conditions of design of pieces. This manufacturing process conditions the functional behaviour of pieces. In this work are presented the preliminary results of a study conducing to obtain the influence of machining parameters in the response to corrosion of aerospace aluminium alloys in seawater. This results show a high influence of feed, and a minor influence of cutting speed.

Study on the effect of vanillin on the corrosion inhibition of aluminum alloy

The effect of vanillin on the corrosion inhibition of aluminum (Al) alloy in seawater was studied by potentiodynamic polarization (PP), linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) techniques. The surface morphology after its exposure to seawater with and without vanillin was examined by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). All the studied parameters showed good inhibitive characteristics against the corrosion of Al alloy in the tested solution, and their performance was observed to increase with the inhibitor concentration. Polarization data indicated that the studied inhibitor is a mixed-type inhibitor. Linear polarization and EIS studies showed that there were significant increases in the overall resistance after the addition of vanillin. The adsorption of inhibitor on Al alloy was found to obey the Langmuir adsorption isotherm. The analysis of SEM and EDS confirmed the formation of precipitates of vanillin on the metal surface, which reduced the overall corrosion reaction.

Tribological behaviors of some polymeric materials in sea water

Ocean tribology, a new research field of tribology, is being established and developing. The investigation on the tribology in sea water has important significance to ocean exploitation. In this paper, the tribological behaviors of UHMWPE, PTFE as well as Ekonol/PTFE, graphite/PTFE and CF/PTFE sliding against GCr15 steel and Ni-Cr-WC alloy in sea water were investigated, and compared with those in pure water. Results show that the main factors that affect the tribological behaviors of five polymeric materials in sea water are the corrosive effect and lubricating effect of sea water. When polymeric materials sliding against GCr15 in sea water, owing to serious corrosion of counterface by sea water, the surface roughness of the counterface increases largely. As a result, the lubricating effect of medium decreases sharply and the plowing effect of counterface increases greatly. So the friction coefficients and wear rates of five materials sliding against GCr15 in sea water are much larger than those under other conditions. Such wear model, depending on the corrosion of counterface by medium, can be called indirect corrosive wear. Under other three conditions, owing to the more superior lubricating effect of sea water than pure water and the better wettability of Ni-Cr-WC than GCr15, the friction coefficients and wear rates of five materials increase in the following order: sliding against Ni-Cr-WC in sea water < sliding against Ni-Cr-WC in pure water < sliding against GCr15 in pure water. Moreover, compared with other materials, CF/PTFE is the one with more superior plowing and wear resistance in pure and sea water, which is a potential frictional material well suitable for pure and sea water lubrication.

Anti-corrosive properties of natural honey on Al–Mg–Si alloy in seawater

Anti-corrosive properties of natural honey on Al–Mg–Si alloy in seawater were evaluated by potentiodynamic polarization (PP), linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) measurements. All the studied parameters showed good anti-corrosive properties against the corrosion of Al–Mg–Si alloy in the tested solution and their performance increases with corrosion resistant concentration. Polarization data indicated that natural honey is a mixed-type corrosion resistant. LPR and EIS studies showed that there were significant increases in the overall resistance after the addition of natural honey. The adsorption of natural honey on the metal surface obeys Langmuir adsorption isotherm. The analysis of morphology studies confirmed the formation of precipitates of natural honey on the metal surface, which reduced the overall corrosion reaction.

Study on Seawater Corrosion of Fe-Al Intermetallic Compound

The corrosion behavior of Fe3Al intermetallic compounds annealed at various temperatures in sea water was studied. The results indicated that both structure ordering and surface oxidation film can significantly improve the anti-corrosion performance of Fe3Al alloys. Furthermore, there was no significant difference in anti-corrosion performance between Fe3Al samples of DO3 and B2 structure. The corrosion mechanism of Fe3Al alloys in seawater was probably as follows: Al element is preferentially corroded, Fe corrosion followed when Al element has been corroded away from the sample surface as well as the reduce ratio of Al becomes smaller than the dissolution ratio of Fe.

Improvement of corrosion resistance of AA6061 alloy by tapioca starch in seawater

This study examines the use of tapioca starch for improvement of corrosion resistance of AA6061 alloy in seawater. Gravimetric, potentiodynamic polarization, linear polarization resistance and electrochemical impedance measurements were employed to study the corrosion behavior of AA6061 alloy in seawater. The electrochemical measurements for AA6061 alloy in seawater showed that the presence of tapioca starch significantly decreases the corrosion rates, corrosion current densities ( i corr), and double layer capacitance ( C dl), simultaneously increases the values of polarization resistance ( R p). The inhibition efficiencies increase with increasing of tapioca starch concentration. The Langmuir adsorption isotherm fits well with the experimental data. The nature of adsorption of tapioca starch on the metal surface has also been examined. The analysis of SEM and EDS confirmed the formation of precipitates of tapioca starch on the metal surface, which reduced the overall corrosion reaction.

Galvanic Corrosion Performance of High-Strength Copper-Nickel Alloys in Seawater

Abstract High-strength copper-nickel (Cu-Ni-Mn-Al-Nb) alloys are widely used for marine applications because of their excellent resistance to seawater corrosion, high inherent resistance to biofouling, and ease of fabrication. However, in-service experience has shown that these alloys may encounter variable performance worldwide as a result of local environmental conditions. In particular, the corrosion performance of high-strength Cu-Ni alloys may be affected by the seawater environmental factors, which may include biofouling, temperature, salinity, pH, and dissolved oxygen content. This study reports an investigation into the galvanic corrosion performance between two wrought, high-strength copper-nickel alloys, with nickel contents of 15% and 19%, regarding the influence of surface oxide films/deposits and biofouling. X-ray photoelectron spectroscopy was used to study the composition of the corrosion product films. Analyses of galvanic currents, coupled and decoupled potentials routinely monitored for ...

Effect of temperature and thiosulphate on the corrosion behaviour of 90‐10 copper‐nickel alloys in seawater

PurposeThe purpose of this paper is to evaluate the effect of seawater temperature on the corrosion behaviour of 90‐10 cupronickel alloys. Also, to investigate the effect of thiosulphate additions (one of the major sulphide oxidation products in seawater) on the alloy corrosion rate in seawater.Design/methodology/approachPotentiodynamic polarization measurement (DC) was used to estimate the corrosion rate of the cupronickel alloy in seawater with and without thiosulphate species (50‐650 ppm).FindingsIt was observed that the cupronickel alloy suffered accelerated corrosion as the seawater temperature was raised from 25 to 50 or 80°C. The increase in the corrosion rate was found to correspond well with the negative shift in the free corrosion potential. Thiosulphate addition was found to depend on the test temperature. At 25°C, thiosulphate activated the alloy dissolution rate and the higher were the thiosulphate concentrations, the higher was the corrosion rate. At 50 or 80°C, however, thiosulphate promoted the dissolution rate at early stages, but seemed to interfere with the surface film formation later on, producing a black film that effectively decreased the alloy corrosion rate. At higher potentials, however, the film became non‐protective, leading to accelerated corrosion once again.Originality/valueThis paper explains the corrosion behaviour of 90‐10 cupronickel alloys in seawater as a function of test temperature and thiosulphate additions.

Electrochemical characteristics of Al-Mg alloy in seawater for leisure ship: Stress corrosion cracking and hydrogen embrittlement

We investigated the mechanical and electrochemical properties of aluminum alloys. Aluminum alloys do not corrode due to the formation of an anti-corrosive passive film, such as Al2O3 or Al2O3·3H2O, which resists corrosion in neutral solutions. In seawater, however, Cl − ions destroy this passive film. The current density in the first passivity range during the application of anodic protection had a similar value as that for concentration polarization by dissolved oxygen during the application of cathodic protection. The current density in the first passivity range had the lowest value overall. The lowest current densities in the potentiostatic and galvanostatic tests occurred at potentials of −1.4 to −0.7 V and −0.9 to −0.7 V, respectively.

Optimization of Corrosion Protection Potential for Stress Corrosion Cracking and Hydrogen Embrittlement of 5083-H112 Alloy in Seawater

We report on the optimum corrosion protection potential range for stress corrosion cracking and hydrogen embrittlement of 5083-H112 Al alloy specimens using electrochemical methods and slow strain rate testing (SSRT) in seawater. In the results of the cathodic polarization curve, the concentration polarization due to dissolved oxygen reduction reaction correspondeds to a protection potential of OCP≈ −1.55 V. However, a potential of −1.2 V in the SSRT showed little effect of atomic hydrogen evolution. Potentials less than −1.6 V are affected by atomic and molecular hydrogen. We thus concluded that the effect of atomic hydrogen predominates. Overall, the optimum corrosion protection range for SCC and hydrogen embrittlement of 5083-H112 seems to be between −0.9 V and −0.7 V.

Electrochemical properties and corrosion inhibition of AA6061 in tropical seawater

The corrosion inhibition of aluminum and its alloys is the subject of tremendous technological importance due to the increased industrial applications of these materials. This study reports the results of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) on the corrosion inhibition of AA6061 aluminum alloys in seawater using sodium benzoate as an inhibitor. The electrochemical measurements for aluminum alloys in seawater after varied immersion period showed that the presence of sodium benzoate significantly decreases the corrosion currents densities ( i corr), corrosion rates and double layer capacitance ( C dl), as simultaneously increase the values of polarization resistance ( R p). Charge transfer process and development of thin film on the specimen have been proven by morphology study using SEM.

A study on the corrosion behavior of aluminum alloys in seawater

In this study, the aluminum alloys AA5083 and AA1100 were tested in seawater at 23 and 60 °C. Polarization plots showed that the alloys suffered from pitting attack. The breakdown potential of the two alloys decreased with an increase in test temperature with better corrosion resistance for alloy 1100. The weight loss tests revealed low corrosion rate values for both alloys, indicating a beneficial use for these alloys in marine environments. The pit morphology on the polarized aluminum alloys showed hemispherical isolated deeper pits on the 5083 alloy. Samples of the 1100 alloy revealed a higher number of shallow pits (more close to patches of general dissolution). The results showed that the type of intermetallic particles in the aluminum alloy played a major role in passivity breakdown and pit morphology in seawater.