Steel In Natural Seawater Research Articles

Protective Properties of Calcareous Deposit Layer for Cathodically Polarized AH36 Steel in Natural Seawater

A calcareous deposit is a by-product of the cathodic polarization in seawater environments. This study presents the results of evaluating the anticorrosion and anti-macro-biofouling effectiveness of a calcareous deposit layer on the surface of the cathodically polarized AH36 structural steel in tropical seawater. The polarization is induced with initial current densities at which the calcareous deposit layer formed with both aragonite and brucite for 12 months continuously. The protective properties of the layer were compared with those of the passive layer from corrosion products under the same environmental conditions. The macro-biofouling in the tropical seawater is observed in the closed and open surfaces of the steel. The comparison of the anticorrosion property shows that, to some degree, the calcareous deposit layer contributes to surface passivation, as in the case of the corrosion product layer. In addition, the composition of the brucite and aragonite in the calcareous layer in the study plays a role as a macro-biofouling growth-limiting factor.

Adsorption behavior of scent leaf extract as corrosion inhibitor for carbon steel in natural sea water

Adsorption behavior of scent leaf extract as corrosion inhibitor for carbon steel in natural sea water

Influence of available chlorine on corrosion behaviour of low alloy marine steel in natural seawater

ABSTRACT Available chlorine is known to play a significant role in metal corrosion due to its oxidising properties. In this paper, the effect of available chlorine concentration on corrosion behaviour of the low alloy marine steel was investigated by electrochemical and immersion tests. Experimental results show that the corrosion rate of low alloy marine steel is accelerated with the increase of available chlorine concentration in seawater. The localised electrochemical dissolution of the steel is more active with the concentration of available chlorine increasing. Energy dispersive spectroscopy (EDS) was performed to understand the composition of the corrosion products that the large enrichment of Cl element occurred for the high available chlorine concentration (100 ppm) after 720 h exposure to seawater. The influence of available chlorine concentration on mechanical property of low alloy marine steel indicatesthe less impact on the tensile and yield strength of the low alloy marine steel.

A study on the influence of silanized clay on the barrier, hydrophobic and mechanical properties of epoxy coated steel in natural seawater

ABSTRACT Diethoxy(3-glycidyloxypropyl) methylsilane (GPMS), a surface modification agent, is used to give halloysite nanoparticles a hydrophobic behaviour and improve their ability to disperse in epoxy polymers (EP). Surface roughness and hydrophobicity (WCA: 144°) are both quite high in EP-GPMS/Clay coatings. The corrosion behavior of coated steel surfaces was investigated using electrochemical methods. The EP-GPMS/clay nanocomposite coating was shown to have about 63 times higher coating resistance than the EP coating. The EP-GPMS/Clay displayed better coating resistance (6687.71 kΩ.cm2) and a lower corrosion current density (4.25 μA/cm2) than plain epoxy (1.01 kΩ.cm2; 287.21 μA/cm2) even after prolonged exposure to the electrolyte, according to electrochemical studies. Compared to the pure EP (0.0599 mm/year), the EP-GPMS/clay coated sample had the lowest corrosion rate (0.0017 mm/year). According to SECM data, at 15 d of immersion, the Fe dissipation at the surface of the EP-GPMS/Clay coating (2.6 nA) is much smaller than the plain EP (14.7 nA). Additionally, the EP-GPMS/Clay showed enhanced adhesive properties. The EP with silanized clay offers an outstanding oxygen and water repellent, hydrophobic, and barrier properties. Due to the environmental safety of clay/silane, this kind of coating might be employed as a workable coating substance for industrial applications.

Biological macrofouling and electrochemical corrosion properties of structural steel AH36 in natural seawater at Hon Tre island, Nha Trang

The biological macrofouling characteristics and electrochemical corrosion behavior of structural steel AH36 in natural seawater were studied continuously for 12 months at Hon Tre Island, Nha Trang – Vietnam. Electrochemical corrosion properties were studied using a PPGS-HHMC12 multi-channel device produced by the Institute of Chemistry, VAST. Tests were conducted at depths of 0.6 m, 1.8 m, and 3.0 m; under anti-macrofouling control, rotary movement, and under laboratory conditions as a comparison option. The results showed that macro-fouling formed and grew rapidly in both quantity, size and biomass in the next 3 months, then slowly and stably increased to about 8 months (6.06 kg.m-2). The OCP shifted to a positive potential, then reached a stable value of about -550 mV during the rest of exposure time. The corrosion current density decreased sharply from the first month to the fourth month, then reached a stable value of about 10 µA.cm-2 in next months of testing. The corrosion rate of AH36 steel in natural seawater in the field was higer than that under laboratory condition, which could be explained by the interaction of many factors such as dissolved oxygen, biofouling, water current, solar radiation

Electrodeposition of Cu-Reinforced Polyaniline Coating for Protection of AH36 Steel in Natural Seawater

The marine environment is highly corrosive for mild and low alloy steels. This study aimed to enhance the corrosion resistance of the AH36 steel in a saline medium by coating it with a copper particles reinforced polyaniline (PANI) layer. PANI and Cu particles were grown on the steel surface by electrodepositing methods. Firstly, PANI was electropolymerized in the presence of oxalic acid, followed by the electrodeposition of Cu particles at different deposition times. The coating showed a well-distribution of Cu particles in the polymer matrix and excellent adhesion. Furthermore, the Cu particles and PANI-coated steels exhibited corrosion resistance significantly in the saline medium compared to the bare substrate and pristine PANI-coated samples. The improved corrosion protection of a Cu@PANI coating on the AH36 steel could contribute to forming a physical barrier by filling Cu particles on the PANI pores.

When material science meets microbial ecology: Bacterial community selection on stainless steels in natural seawater

The passive film depends on the alloy's composition and the exposure conditions. How the surface composition affects the selection of microbial biofilms though, has not been fully elucidated or incorporated into the analysis of corrosive biofilms. The degradation of stainless steel (SS) exposed to natural seawater was studied to understand how the oxide layer composition of SS could affect the selection and variability of the bacterial community. To accomplish this goal, austenitic and superferritic SS grades were exposed to natural seawater on the central coast of Chile. The deterioration of steel and qualitative description of biofilm formation was monitored at different exposure periods. Biofilms were evaluated based on massive sequencing analysis of the bacterial community and subsequent ecological studies. The results revealed that variability of the calculated corrosion rate correlated with the similarity of the bacterial community within samples from each SS and its corrosion inferred capacity. The associated bacterial families showed a higher representation in SSs with a more significant increase in the Fe/Cr ratio over the exposure time. These findings revealed that iron content in the oxide layer represents a key feature of the surface composition for selecting bacterial assemblages in marine environments.

Sand impingements on cathodic protection of marine carbon steel in natural sea water

ABSTRACT In this work, the influence of sand impingements on cathodic protection (CP) of marine carbon steel in natural sea water was studied in comparison with the CP performances in static and flowing sea water without sand particles. Results show that the propagation of local active anodic dissolution at the steel inclusions could be totally inhibited by providing sufficient cathodic current in the sea water free of sand particles. However, the local ‘CP shielding’, potential fluctuation and sand impingements would enhance the anodic dissolution at inclusions, thus leading to the occurrence of erosion-corrosion under CP. The negative shift of the CP potential could not retard the propagation of erosion-corrosion pits under sand impingements. The synergy of erosion and corrosion might result in long-term failure of local CP.

Impact of zinc ion addition on corrosion of EH40 steel in natural seawater

AbstractZinc ion is a common heavy metal in marine pollution, but its impact on corrosion of steels without passive films in natural seawater is far from being investigated. In this study, the impact of zinc ion addition (1.5 and 15 mmol/L) on corrosion of EH40 steel commonly utilized for building ships and offshore platforms was studied by numerous methods and technologies. It was found that EH40 steel corrosion was inhibited with the addition of zinc ion, and corrosion inhibition efficiency increased with the concentration added. The deposited ZnO and Zn(OH)2 on the steel surface was believed to hamper electron transfer, thus inhibiting corrosion. Meanwhile, the bactericidal zinc ion and ZnO mitigated the activity of microorganisms in biofilms to reduce the damage caused by microbiologically influenced corrosion. But pitting corrosion was enhanced with a high concentration of zinc ion added due to the inhomogeneity of ZnO layers.

Superior barrier, hydrophobic, and mechanical properties of the epoxy nanocomposite containing mixed metal oxides

Newly synthesized 3-amino-1,2,4-triazole-5-thiol (ATT) functionalized Al2O3-ZnO nanoparticles were added to epoxy resin (EP). The anticorrosion properties of newly synthesised formulations like EP/Al2O3-ZnO and EP-ATT/Al2O3-ZnO nanocomposite coated steel samples were investigated electrochemically using scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy (EIS). In natural seawater, EIS experiments indicated outstanding protective behaviour for the EP-ATT/Al O3-ZnO coated steel. The EP-ATT/Al2O3-ZnO nanocomposite coating resistance was reported to be 2110.44 kΩ·cm2, whereas EP/Al2O3-ZnO coating (1730.45 kΩ·cm2) and pure epoxy coating (61.21 kΩ·cm2) had lesser coating resistance. The coating resistance of EP-ATT/Al2O3-ZnO nanocomposite was found to be more than 34% greater than that of PU coating. The measured current by SECM analysis over the EP-ATT/Al2O3-ZnO nanocomposite coating was very low (1.6 nA) compared to EP/Al2O3-ZnO (3.7 nA) and pure epoxy coated steel (5.9 nA). The surface morphological studies of the coated steel by SEM/EDX analysis and X-ray diffraction (XRD) analysis revealed that the Al2O3-ZnO nanoparticles were enriched at the corrosion products which prevented corrosion initiation processes. The peel strength of the EP-ATT/Al2O3-ZnO nanocomposite film was found to be 982 ± 13 N/cm when the concentration of ATT/Al2O3-ZnO nanoparticles was 2 wt.%. Moreover, the resultant EP-ATT/Al2O3-ZnO formulation exhibited an excellent hydrophobic behaviour (WCA: 117°). Therefore, it was concluded from the electrochemical and mechanical investigation that the newly synthesized EP-ATT/Al2O3-ZnO nanocomposite provided an excellent barrier and mechanical properties due to the addition of ATT/Al2O3-ZnO nanoparticles to the epoxy resin which prevented the degradation of materials and helped to prolong the life of the coated steel. HIGHLIGHTS Electrochemical studies revealed excellent coating resistance and a decreased corrosion current density for the EP-ATT/Al2O3-ZnO coated steel in natural seawater It was found that the coating resistance of EP-ATT/Al2O3-ZnO nanocomposite was over 34% higher than that of the epoxy coating. The EP-ATT/Al2O3-ZnO coating retarded the propagation of aggressive ions to the coating/steel interface. The reinforcement of ATT/Al2O3-ZnO nanoparticles in the epoxy coating exhibited a smooth microstructure producing superior corrosion protection and excellent hydrophobic and dynamic mechanical properties. The addition of ATT/Al2O3-ZnO nanoparticles to the epoxy prevented the degradation of materials and helped to prolong the life of the coated steel.

Flow accelerated corrosion and erosion\u2212corrosion behavior of marine carbon steel in natural seawater

In this work, flow accelerated corrosion (FAC) and erosion−corrosion of marine carbon steel in natural seawater were electrochemically studied using a submerged impingement jet system. Results show that the formation of a relatively compact rust layer in flowing natural seawater would lead to the FAC pattern change from ‘flow marks’ to pits. The increase of the flow velocity was found to have a negligible influence on the FAC rate at velocities of 5−8 m s−1. The synergy of mechanical erosion and electrochemical corrosion is the main contributor to the total steel loss under erosion−corrosion. The increase of the sand impact energy could induce the pitting damage and accelerate the steel degradation. The accumulation of the rust inside the pits could facilitate the longitudinal growth of the pits, however, the accumulated rusts retard the erosion of the pit bottom. The erosion and corrosion could work together to cause the steel peeling at the pit boundary. The steel degradation would gradually change from corrosion-dominated to erosion-dominated along with the impact energy increasing.

Synergistic effect of polybenzoxazine/ZrO2 encapsulated polyurethane nanocomposite coatings for enhanced barrier properties of steel in seawater

PurposeThe purpose of this study is to use polybenzoxazine (Pbz) functionalized ZrO2 nanoparticles to synthesize polyurethane (PU)-PbZ/ZrO2 nanocomposite. The results derived from the electrochemical impedance spectroscopy (EIS) and polarization studies indicated the superior anticorrosive activity of PU-Pbz/ZrO2 nanocomposite coatings compared to those of plain PU coatings. The decreased corrosion current was detected on the scratch of the PU-Pbz/ZrO2 nanocomposite-coated mild steel surface by scanning electrochemical microscopy (SECM) compared to other studied coatings. The superior anticorrosive and mechanical properties of the proposed nanocomposite coatings provide a new horizon in the development of high-performance anticorrosive coatings for various industries.Design/methodology/approachThe Pbz functionalized ZrO2 nanoparticles were characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) and thermogravimetric analysis (TGA) in terms of the structural, morphological and thermal properties of these coatings. A different formulation of coatings such as PU, PU-Pbz, PU-ZrO2 and PU-Pbz/ZrO2 were prepared and investigated for their corrosion protection performance on mild steel in natural seawater by electrochemical techniques. The surface morphological studies were done by SEM/EDX and XRD analysis.FindingsThe superior anticorrosive property of the proposed nanocomposite coatings provides a new horizon in the development of high-performance anticorrosive coatings for various industries. Addition of Pbz wrapped ZrO2 nanoparticles into the PU coating resulted in the blockage of charge transfer at the metal/electrolyte interface, which reduced the dissolution of mild steel. It was revealed from the SEM/EDX analysis that the formation of the corrosion products at the metal/electrolyte interface behaved as the passive layer which reduced the dissolution of steel.Originality/valueThe inclusion of polybenzoxazine functionalized ZrO2 nanoparticles to the polyurethane coating reinforces the barrier and mechanical properties of PU-Pbz/ZrO2 nanocomposite, which is due to the synergistic effect of ZrO2 and Pbz.

High protection performance of vanadium pentoxide-embedded polyfuran/epoxy coatings on mild steel

V2O5-incorporated polyfuran (PF) as nanofiller(V2O5-PF) was used to synthesize epoxy (EP)-PF/V2O5 nanocomposites. The PF-functionalized V2O5 nanoparticles were characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The corrosion protection performance of these coatings on mild steel in natural seawater was determined by electrochemical measurements. Results from electrochemical techniques revealed the superior anticorrosive activity of nanocomposite coatings compared to those of plain epoxy coatings. The superior anticorrosive property of the proposed nanocomposite coatings provides a new horizon in the development of high-performance anticorrosive coatings for various industries. Incorporating PF-functionalized V2O5 nanoparticles into the epoxy coating ensued in the blockage of charge transfer at metal–electrolyte interface which hindered the dissolution of metal/alloy. Scanning electrochemical microscopic (SECM) studies detected lower corrosion current on the EP-PF/V2O5 nanocomposite coated mild steel surface. SEM/EDX analysis examined the corrosion products which acted as the passive layer that reduced the dissolution of steel. The inclusion of PF-functionalized V2O5 nanoparticles to EP improved the mechanical properties of the coated surface which complimented the electrochemical studies.

The effect of polymeric protective layers and the immersion time on the corrosion behavior of naval steel in natural seawater

Evaluation of corrosion behavior of E32 naval steel with sandblasted surface and without corrosion protection coating was performed using electrochemical methods. It was compared to the corrosion resistance of the E32 surfaces coated with polymeric film for corrosion protection, respectively the naval steel E32 coated with an epoxy primer and E32 naval steel coated with epoxy primer over which polyurethane acrylic paint. Corrosion characterization was performed using electrochemical methods, following the influence of time on the corrosion process resulting from the interaction of E32 steel with and without anticorrosive protection coatings. In this case, the monitoring time was 98 days (14 weeks) and the electrochemical measurement protocol was repeated every week. Electrochemical measurements show that the epoxy primer on which a polyurethane acrylic paint was applied as a corrosion protection method for the E32 naval steel substrate improves the corrosion resistance of naval steel E32 in natural sea water.

Electrochemical behavior of (Cr, W, Al, Ti, Si)N multilayer coating on nitrided AISI 316L steel in natural seawater

AISI 316L steel is often used in materials applied toward nuclear power but are subjected to pitting corrosion in a marine environment. In this study, (Cr, W, Al, Ti, Si)N multilayer coatings were deposited using multi-arc ion plating on the surface of non-nitrided and nitrided AISI 316L steel. The microstructure and corrosion resistance of four different systems were investigated, namely, (i) untreated AISI 316L steel, (ii) plasma nitrided (PN), (iii) coated on an untreated matrix (coating) only, and (iv) coated on nitrided (hybrid) specimens. The phase structures, morphologies, and compositions of the different specimens were characterized using X-ray diffraction, transmission electron microscope, Atomic Force Microscope, scanning electron microscope, X-ray photoelectron spectroscopy, and energy dispersive x-ray spectroscopy. The results show that a thin CrWAlTiSiN multilayer coating, approximately 2.3 μm in thickness, is deposited on the surface of an ~12 μm nitrided layer. Potentio-dynamic polarization and electrochemical impedance spectroscopy were used to evaluate the assessment of the electrochemical behavior in the natural seawater of China's Yellow Sea. The hybrid specimens exhibited excellent corrosion resistance compared to both the nitrided and coated specimens.

Corrosion of Carbon Steel in Marine Environments: Role of the Corrosion Product Layer

This article presents a synthesis of recent studies focused on the corrosion product layers forming on carbon steel in natural seawater and the link between the composition of these layers and the corrosion mechanisms. Additional new experimental results are also presented to enlighten some important points. First, the composition and stratification of the layers produced by uniform corrosion are described. A focus is made on the mechanism of formation of the sulfate green rust because this compound is the first solid phase to precipitate from the dissolved species produced by the corrosion of the steel surface. Secondly, localized corrosion processes are discussed. In any case, they involve galvanic couplings between anodic and cathodic zones of the metal surface and are often associated with heterogeneous corrosion product layers. The variations of the composition of these layers with the anodic/cathodic character of the underlying metal surface, and in particular the changes in magnetite content, are thoroughly described and analyzed to enlighten the self-sustaining ability of the process. Finally, corrosion product layers formed on permanently immersed steel surfaces were exposed to air. Their drying and oxidation induced the formation of akaganeite, a common product of marine atmospheric corrosion that was, however, not detected on the steel surface after the permanent immersion period.

Commercial aqueous additives as used eco-friendly corrosion inhibitors for carbon steel in natural seawater

Commercial aqueous additives as used eco-friendly corrosion inhibitors for carbon steel in natural seawater

Reduction of potential ennoblement of stainless steel in natural seawater by an ecofriendly biopolymer

The effect of biofilm formation on passive stainless steel in seawater environments is of primary importance since it leads to potential ennoblement of surfaces and subsequently to localized corrosion such as pitting and crevice corrosion. This study aims at developing an ecofriendly alginate biopolymer containing both non-toxic calcium and a limited amount of biocidal zinc ions which inhibits this effect. For this purpose, calcium alginate containing less than 1 % of zinc ions localized in the vicinity of the steel surface in natural and renewed seawater is demonstrated to reduce significantly the ennoblement process of steel. After 1 month of immersion, a mass loss of only 4 % of the active material is observed authorizing thereby long-term protection of steel in real environment.

Anticorrosion performance of acriflavine–Zn2+ system for mild steel in seawater utilization

An organic/inorganic hybrid corrosion inhibitor based on acriflavine/zinc acetate in controlling corrosion of mild steel in natural seawater was studied through electrochemical techniques, scanning electron microscopy (SEM-EDX), X-ray photoelectron spectroscopy (XPS) and quantum chemical calculations. The experimental results demonstrated the incorporation of acriflavine and Zn2+ significantly improve the uniformity and corrosion resistance of the protective film, and showed a synergistic inhibition effect. Electrochemical measurements indicated the acriflavine acts as a mixed-type inhibitor, and the acriflavine-Zn2+ complex acts as an anodic inhibitor. The optimal mass ratio of acriflavine to Zn2+ was found to be 1:1 in view of the inhibition efficiency of polarization curves. Surface analysis verified the formation and characteristic of acriflavine-Zn2+ film on steel surface. The complex film was mainly composed of Zn(OH)2, [Fe(III), Zn(II)–AF] and oxides/hydroxides of iron(III) based on XPS analysis.

Stress corrosion behavior of X80 pipeline steel in natural seawater with different dissolved oxygen

Slow strain rate stress corrosion test of X80 steel in the natural seawater are carried out to study to effect of dissolved oxygen on the sensitivity of stress corrosion. Scanning electron microscope (SEM) combined electrochemical measurement are adopted to analyze mechanism and the influencing factor of stress corrosion cracking. The results show that the sensitivity of SCC in the natural seawater increases, and the stress corrosion cracking gradually transforms from ductile to quasi-brittle fracture, with the increase of dissolved oxygen. Tafle polarization and electrochemical impedance spectroscopy of X80 show that dissolved oxygen aggravates electrochemical corrosion and reduces corrosion resistance. Corrosion pits and micro cracks at the lateral and fracture surface trigger stress concentration and promote anodic dissolution under stress, thereby accelerate the process of stress corrosion cracking of X80 steel in the seawater.