Alloys In Seawater Research Articles

Improvement of Corrosion Properties of AL-4.08MG Alloy in Seawater by Two Step Anodizing in Electrolyte with Varied Concentration

Aluminum is extremely active metal on the surface of which the oxide is instantly created when exposed to atmosphere. This naturally generated film has little industrial value as it has thickness as thin as 10 nm. Hence, oxide films are often made thick by electrochemical method. The characteristics of the films can be controlled by varying process parameters including composition, concentration, additives, solution temperature, voltage etc. These films have high hardness and excellent corrosion resistance. Therefore, they are receiving great amount of attention in both academic and industrial areas with their diverse applicability. In this paper, the optimal electrolyte concentration was investigated to produce oxide film with excellent corrosion resistance. The results reveal that Al2O3 oxide film was created on the surface for all tested electrolyte concentrations. Moreover, the films have a considerably lower corrosion current density than that of the substrate, implying excellent corrosion resistance.

Tribological properties of bronze–Cr–Ag alloy in seawater, NaCl solution and deionized water

Tribological properties of bronze–Cr–Ag alloy sliding against AISI 52,100 steel were investigated in deionized water, 3.5wt% NaCl solution and seawater. The friction coefficient and wear rate of the alloy follow the sequence: deionized water>NaCl solution>seawater. In NaCl solution and seawater, Cu2O, Al(OH)3, FeOOH and Fe2O3 form on the surface because of chloride corrosion. In seawater, CaCO3 and Mg(OH)2 are adsorbed on the surface. The above compounds play an important role in reducing the friction and wear. The study of tribocorrosion mechanism is beneficial for bronze–Cr–Ag alloy to be used in sliding bearing under seawater condition.

Effect of 3 wt% Al Content and Rapid Solidification on the Erosion-corrosion Behavior of 92 wt% Cu and 5 wt% Ni Alloy in Seawater

Effect of 3 wt% Al Content and Rapid Solidification on the Erosion-corrosion Behavior of 92 wt% Cu and 5 wt% Ni Alloy in Seawater

Influence of the negative bias in ion plating on the microstructural and tribological performances of Ti–Si–N coatings in seawater

The TiSiN coatings were deposited on Ti6Al4V alloy by multi-arc ion plating with different substrate negative bias to improve the tribological properties of titanium alloy in seawater. The TiSiN coatings have a coupled structure of amorphous Si3N4 and nanocrystalline TiN. The grain size decreases and the coatings become dense with the increase of the negative bias. The hardness of TiSiN coatings increases from 39GPa to 47GPa with the increase of substrate negative bias from 10V to 40V. The tribological tests reveal that the TiSiN coatings have a lower friction coefficient and higher wear rate in seawater compared with in atmosphere. Moreover, the wear rates increase with the increase of bias voltage. The TiSiN coating deposited at bias voltage of 10V shows the best tribological properties in seawater.

Assessing the corrosion-wear behaviours of Hastelloy C276 alloy in seawater

A systematic investigation has been carried out in the present work to study the electrochemical and corrosion–wear behaviours of Hastelloy C276 alloy sliding against Al2O3 pin in artificial seawater, using a pin-on-disc tribometer integrated with a potentiostat for electrochemical control. It can be observed that the cathodic shift of open circuit potential and three order of magnitude increase of current density formed due to sliding. The total corrosion–wear loss increases with increasing applied potential. Interestingly, the total material loss at the applied potential of 0.5 and 0.9 V is more than two times of that of pure mechanical wear, confirming the synergy between wear and corrosion. And, the contributions of wear-induced corrosion (ΔKc) and corrosion-induced wear (ΔKw) are dominant, especially at higher applied potentials. Copyright © 2015 John Wiley & Sons, Ltd.

Discharge behavior and electrochemical properties of Mg–Al–Sn alloy anode for seawater activated battery

Mg–Al–Sn alloy is one of the new developed anode materials for seawater activated batteries. The potentiodynamic polarization, galvanostatic discharge and electrochemical impedance spectroscopy of Mg–6%Al–1%Sn and Mg–6%Al–5%Sn (mass fraction) alloys in seawater were studied and compared with the commercial AZ31 and AP65 alloys. The results show that the Mg–6%Al–1%Sn alloy obtains the most negative discharge potential of average –1.611 V with a electric current density of 100 mA/cm2. EIS studies reveal that the Mg–Al–Sn alloy/seawater interfacial electrochemical process is determined by an activation controlled reaction. The assembled prototype batteries with Mg–6%Al–1%Sn alloy as anodes and AgCl as cathodes exhibit a satisfactory integrated discharge properties.

Influence of Friction Stir Welding on Corrosion Properties of Aw-7020M Alloy in Sea Water

Abstract Friction Stir Welding (FSW), provides an alternative to MIG and TIG welding methods for joining aluminium alloys. The article presents the results of electrochemical corrosion resistance test of alloy AW- 7020M and its joints welded by FSW. The study was performed using the method of electrochemical impedance spectroscopy (EIS). Impedance spectroscopy studies showed that both, the FSW welded joint and base material AW-7020M has a good resistance to electrochemical corrosion in sea water environment, wherein the welded joint has a higher susceptibility to this type of corrosion. Research has indicated the desirability of applying the FSW method for joining AW-7020M alloy in shipbuilding industry.

Corrosion Propensity of Cold Deformed 5052 Aluminium Alloy in Seawater

Conventional 5052 aluminium alloysare known to exhibit characteristics response to deformation having a rebound effect on their corrosion propensity. This study investigates this phenomenon with a view to establishing the appropriate processing method that confers enhanced corrosion resistance to stem the incidence of facility failure in the food processing industry. Samples of the alloy were produced by casting after proper charge calculation. The cast samples were cold rolled in a two-high mill at ambient temperature to 20%, 40%, 60% and 80% size reduction. Corrosion test coupons were then prepared from the deformed samples on which electrochemical corrosion polarisation in seawater environment for 36 hours at an interval of 6 hours was carried out. Results of the corrosion campaigns show that corrosion rate increases as degree of deformation increases and this is attributed to high energy density in the deformed sample matrix which approximates initiation sites for corrosion.

Anti-Corrosive Performances of Environmental Friendly Materials on Al-Mg-Si Alloy

The anti-corrosive performances of aluminum and its alloys is the subject of considerable technological importance due to the increased industrial applications of these materials. This paper reports the results of the linear polarization (LP) and electrochemical impedance spectroscopy (EIS) measurements on the corrosion inhibition of Al-Mg-Si alloy in seawater using natural products (natural honey, vanillin and tapioca starch) as an inhibitor. The results show that the anti-corrosive performances increases with the increasing of natural products concentration. The energy dispersive spectrometer (EDS) studies elucidated that the breakdowns of Al2O3 after exposed to seawater decreased with the presence of natural products. In all cases, the anti-corrosive performances can be given in the following increasing order: Natural honey < Vanillin < Tapioca starch.

Corrosion behavior of leaded-bronze alloys in sea water

The corrosion behavior of leaded-bronze alloys (Cu–5Sn–5Zn–5Pb, Cu–8Sn–8Zn–8Pb and Cu–10Sn–10Zn–10Pb) in sea water was investigated using weight loss method, open-circuit potential measurements (OCP), polarization techniques and electrochemical impedance spectroscopy (EIS). The nature and morphology of the corrosion products were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that the corrosion resistance decreases with decreasing copper content. The XRD indicated that the composition of patina depends on the concentration of Cu, Sn, Zn and Pb in each alloy.

The Corrosion Behavior of Cu-Ni-Si Alloy in Sea Water with Deep-Sea Bacteria

The corrosion behavior of Cu-Ni-Si alloy exposed to a nutrient-rich simulated seawater-based nutrient-rich medium in the presence of a deep-sea bacterial (Erythrobacter pelagi sp.nov) was investigated by metallographic microstructure observation, electrochemical impedance spectroscopy (EIS) measurement. It was demonstrated that the charge transfer resistance (Rct) and the resistance of oxide film (Rf) dramatically increased within 2 days then gradually decrease and becoming stable because of an patchy or blotchy biofilm formed on the surface of the alloy.

Corrosion behavior of ZHMn55-3-1 copper alloy in stagnant and flowing seawater with entrained sediment

Purpose – The purpose of this investigation was to study the erosion-corrosion behavior of ZHMn55-3-1 copper alloy in seawater (flow velocity from 0 to 0.8 m/s, sediment content from 0 to 0.15 percent), to analyze the effects of the flow velocity and sediment content on the erosion-corrosion process. Design/methodology/approach – A simulated erosion-corrosion test system was set up. Weight loss determinations and electrochemical measurements (such as potentiostat square wave (PSW), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests) were used to study the erosion-corrosion behavior of ZHMn55-3-1 copper alloy in stagnant and flowing seawater with different sediment contents. Findings – Under the test conditions, ZHMn55-3-1 copper alloys had good corrosion resistance to stagnant clear seawater, while increasing the flow velocity and sediment content reduced the corrosion resistance of the material. The difference in the erosion-corrosion mechanism between flow velocity and sediment content was that the former affected both the cathode process and the anode process of electrochemical corrosion, while the latter essentially affected only the anode process. Originality/value – This paper explains the effects of flow velocity and sediment content on the erosion-corrosion behavior of ZHMn55-3-1 copper alloy in flowing seawater.

X-ray photoelectron spectroscopy depth-profiling analysis of surface films formed on Cu–Ni (90/10) alloy in seawater in the absence and presence of 1,2,3-benzotriazole

X-ray photoelectron spectroscopy (XPS) depth-profiling analysis was performed to investigate the chemical composition of the film formed on Cu–Ni (90/10) alloy in seawater and sulphide-polluted seawater in the absence and presence of an inhibitor, 1,2,3-benzotraizole (BTAH). The chemical composition of the film is found to vary at different depths of the film. In seawater environment, the outermost layer is found to consist of CuO, Cu(OH)2 and Cu2O. After sputtering for 12min, the major constituent of the film is Cu2O. In seawater polluted with sulphide also the outermost layer is found to consist of CuO, Cu(OH)2 and Cu2O without any Cu2S or CuS. After 4min of sputtering only, the peaks due to Cu2S and CuS are detected and the major constituent of the film is still Cu2O. The sulphides of copper are absent after 8min of sputtering. In the presence of BTAH, the XPS of the film showed peaks due to carbon and nitrogen up to 4min of sputtering. This result reveals the presence of the [Cu(I)BTA]n complex on the alloy surface in both seawater and sulphide-polluted seawater. The percentage of Cu2O is found to be much less than that found in the absence of inhibitor. In both the stated environments, in the absence of BTAH, the oxygen concentration is reduced to a small value only after 20min of sputtering. Whereas, in the presence of BTAH, the concentration of oxygen is reduced to a very small value after sputtering for 12min. These results infer the protective ability of the BTAH film on Cu–Ni (90/10) alloy in both seawater and sulphide-polluted seawater even after 30days of immersion.

The study of marine corrosion of copper alloys in chlorinated condenser cooling circuits: The role of microbiological components

The present paper reports the on-line monitoring of corrosion behavior of the CuNi 70:30 and Al brass alloys exposed to seawater and complementary offline microbiological analyses.An electrochemical equipment with sensors specifically set for industrial application and suitable to estimate the corrosion (by linear polarization resistance technique), the biofilm growth (by the BIOX electrochemical probe), the chlorination treatment and other physical-chemical parameters of the water has been used for the on-line monitoring.In order to identify and better characterize the bacteria community present on copper alloys, tube samples were collected after a long period (1year) and short period (2days) of exposition to treated natural seawater (TNSW) and natural seawater (NSW).From the collected samples, molecular techniques such as DNA extraction, polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE) and identification by sequencing were performed to better characterize and identify the microbial biodiversity present in the samples.The monitoring data confirmed the significant role played by biofouling deposition against the passivity of these Cu alloys in seawater and the positive influence of antifouling treatments based on low level dosages.Molecular analysis indicated biodiversity with the presence of Marinobacter, Alteromonas and Pseudomonas species.

Potentiostatic corrosion protection technology under cavitation condition for 5083-H116 Al alloy

This study aims to characterize the cavitation damage behavior of aluminum alloys in seawater and thus to enhance its cavitation resistance. Potentiostatic experiments were performed under various potential conditions to determine the optimum protection potentials, at which cavitation damage was suppressed. A potential range was selected for the experiment from −2.2 to −1.4 V, which corresponded to the concentration and activation polarization regions on the cathodic polarization curve of the 5083-H116 alloy. After the experiments, the current density–time behavior was investigated, and the degree of surface damage was observed using three-dimensional microscopy and scanning electron microscopy (SEM). The optimum protection potential was determined to be in the range of −1.9 to −1.5 V under which the cavitation damage was reduced significantly.

Filtration–UV irradiation as an option for mitigating the risk of microbiologically influenced corrosion of subsea construction alloys in seawater

The effect of filtration–UV irradiation of seawater on the biofilm activity on several offshore structural alloys was evaluated in a continuous flow system over 90days. Biofilms ennobled the electrode potential by +400 to 500mV within a few days of exposure to raw untreated seawater. Filtration–UV irradiation of the seawater delayed the ennoblement of the steels for up to 40days and lowered localized corrosion rates in susceptible alloys. Ennobling biofilms were composed of microbial cells, diatoms and extracellular polymeric substances and the bacterial community in biofilms was affected by both the alloy composition and seawater treatment.

Effect of Hydrodynamic Conditions on Corrosion Inhibition of Cu–Ni (90/10) Alloy in Seawater and Sulphide Containing Seawater Using 1,2,3-Benzotriazole

Electrochemical studies of the effect of hydrodynamic conditions on corrosion inhibition of Cu–Ni (90/10) alloy in synthetic seawater and sulphide containing synthetic seawater by 1,2,3-benzotriazole (BTAH) are presented. Impedance, potentiodynamic polarization and cyclic voltammetric (CV) studies are employed in the present investigation. The studies are carried out by using Cu–Ni (90/10) alloy rotating disc electrode at different rotation speeds and at different immersion periods. Reynolds numbers at each rotation speed infer that the flow of seawater is laminar. With increasing rotation speed of the electrode immersed in seawater without sulphide and BTAH, both the charge transfer resistance (Rct) and film resistance (Rfilm) are increased. However, in the presence of sulphide ions and without BTAH, both the Rct and Rfilm are found to decrease with increasing rotation speed at identical immersion periods. Interestingly, when BTAH is added to seawater or seawater containing sulphide, both the Rct and Rfilm are increased to such a great extent that an inhibition efficiency of 99.99% is obtained. In the presence of BTAH, the phase angle Bode plots are more broadened and the maximum values of phase angle are increased to a value close to 90° as the rotation speed is increased. The BTAH film is highly protective even under hydrodynamic condition also. Potentiodynamic polarization studies infer that BTAH functions as a mixed inhibitor under hydrodynamic conditions also. CV studies reveal that the protective BTAH film is stable even at anodic potentials of +850 mV vs Ag/AgCl.

5-(3-Aminophenyl)tetrazole – A new corrosion inhibitor for Cu–Ni (90/10) alloy in seawater and sulphide containing seawater

The inhibition performance of 5-(3-aminophenyl)tetrazole (APT) in controlling corrosion of Cu–Ni (90/10) alloy in synthetic seawater and synthetic seawater containing 10ppm sulphide has been investigated. Electrochemical impedance, potentiodynamic polarization, cyclic voltammetry (CV) weight-loss and scanning electron microscopy (SEM)/energy dispersive X-ray analysis (EDX) studies were employed to evaluate the inhibitor performance. The results of impedance studies show that both charge transfer resistance and film resistance increase with an increase in APT concentration and at a concentration of 6.5mM, APT functions as an excellent inhibitor with an inhibition efficiency of 99.72%. The phase angle Bode plots are more broadened and showed a phase maximum of 81° in the presence of APT. The APT film is highly protective even at a temperature of 60°C. Potentiodynamic polarization studies inferred that APT functions as a mixed inhibitor. CV studies revealed that the protective APT film is stable even up to anodic potentials of +850mV vs. Ag/AgCl. Weight-loss studies showed an inhibition efficiency of more than 99% in the presence of APT even after 30days immersion period. SEM–EDX studies confirm the absence of any corrosion and presence of protective APT film on the alloy surface.

Investigation on corrosion fatigue crack growth rate in 7075 aluminum alloy

The corrosion fatigue crack growth behaviors of 7075 alloy in seawater were investigated. The results showed that corrosion solution concentration, pH value, temperature as well as load frequency have great influences on the corrosion fatigue crack growth rate. The corrosion fatigue crack growth rate in 7075 alloy accelerates with increasing the corrosion solution concentration, raising the temperature, or lowering the pH value. The above three factors can be simply expressed by the surface current intensity, Icor. On the other hand, the corrosion fatigue crack growth rate increases with decreasing the load frequency, due to the longer exposure of the new-generated specimen surface to the corrosive environment. The fracture surface indicated that the corrosion pits extending along the direction of the crack growth are responsible for the acceleration of the crack growth rates, since the corrosion pits may act as physical defects and stress concentrations around the crack-tip. Furthermore, the electrochemical reaction occurring between the new-generated surface and the corrosion solution makes the crack closure difficult, which also facilitates the crack growth. In addition, a modified Paris model has been proposed on the basis of the experimental results, consisting of the surface current intensity Icor and the load frequency f.

Corrosion Inhibition of Cu-Ni (90/10) Alloy in Seawater and Sulphide-Polluted Seawater Environments by 1,2,3-Benzotriazole

The inhibiting effect of 1,2,3-benzotriazole (BTAH) against the corrosion of Cu-Ni (90/10) alloy in seawater and seawater polluted with inorganic sulphide was studied by electrochemical impedance studies (EISs), potentiodynamic polarization studies, and cyclic voltammetric (CV) and weight-loss studies. Surface examination studies were carried out by X-ray photo electron spectroscopy (XPS) and scanning electron microscopy (SEM)/energy dispersive X-ray analysis (EDX). EIS studies have been carried out in seawater and 10 ppm of inorganic sulphide containing seawater in the absence and presence of BTAH at different concentrations, different immersion periods, and at different temperatures. Appropriate equivalent circuit model was used to calculate the impedance parameters. The potentiodynamic polarization studies inferred that BTAH functions as a mixed inhibitor. The impedance, polarization, and weight-loss studies showed that the inhibition efficiency of BTAH is in the range between 99.97 and 99.30% under different conditions. Cyclic voltammeric studies show the stability of the protective BTAH film even at anodic potentials of +550 mV versus Ag/AgCl. All these studies infer that BTAH functions as an excellent inhibitor for Cu-Ni (90/10) alloy in seawater and sulphide-polluted seawater. XPS and SEM-EDX studies confirm the presence of protective BTAH film on the alloy surface.