Immersion Corrosion Tests Research Articles

Comparative Study of Corrosion Behavior of LPCVD-Ti0.17Al0.83N and PVD-Ti1−xAlxN Coatings

In the present work, a low-pressure chemical vapor deposition (LPCVD) Ti0.17Al0.83N and state-of-the-art arc ion plating PVD-Ti1−xAlxN (x = 0.25, 0.55, 0.60, 0.67) coatings were deposited on cemented carbide substrate. The morphological, structural, and electrochemical properties of LPCVD-Ti0.17Al0.83N and PVD-Ti1−xAlxN coatings were compared. The X-ray diffraction (XRD) results and scanning electron microscopy (SEM) images revealed that the LPCVD-Ti0.17Al0.83N coating had a face-centered cubic (fcc) structure, while presenting a crack-free surface morphology and a compressive residual stress of −131.9 MPa. The PVD coatings with a composition of x ≤ 0.60 had an fcc structure, while the PVD-Ti0.33Al0.67N coating consisted of fcc and w-AlN phases. The results of the electrochemical corrosion test showed that the LPCVD-Ti0.17Al0.83N coating had the lowest corrosion current density in a 3.5 wt.% NaCl solution. After a 20-day immersion corrosion test in a 5 mol/L HCl solution, the LPCVD-Ti0.17Al0.83N coating displayed higher stability than the PVD-Ti1−xAlxN coating. The results of electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) analysis revealed that more uniform and denser passivation film, as well as higher Al2O3 proportion in the Al2O3/TiO2 composite passive layer, led to the outstanding corrosion resistance of the LPCVD-Ti0.17Al0.83N coating.

Influence of processing and microstructure on the corrosion behavior of ultrafine grained Al 5083 alloy

Ultrafine grained (UFG) material has received significant research interest due to its combination of strength and toughness when compared with its coarse-grained counterpart. In the present investigation, a distinct UFG microstructure of Al 5083 alloy fabricated through cryorolling (CR), CR followed by warm rolling (WR), and CR followed by short annealing (SA) have been subjected to salt immersion, polarization, and intergranular corrosion tests in 3.5% NaCl solution. A salt immersion test revealed that UFG structures have resistance to pitting corrosion for all conditions when compared to their coarse-grained counterpart. The presence of coarse intermetallic second phase particles leads to the formation of micro galvanic cells with matrix resulting in highly localized pitting corrosion in the solution treated (ST) material, whereas crystallographic pits along the lateral direction have been observed in deformed material. The lower values of corrosion current density ( icorr = 3.640 and 3.910 μA/cm2) were observed for CR and WR conditions, respectively, than ST samples ( icorr = 8.140 μA/cm2) were attributed to the presence of a higher volume fraction of low angle grain boundaries along with a high density of dislocations. SA after CR has slightly increased the corrosion current ( icorr = 3.8 μA/cm2) values thereby shifting the corrosion potentials to a noble direction.

Experimental study on corrosion characteristics of ATOMET 4601 + TiC alloy steels

Abstract The corrosion characteristics of newly synthesized (ATOMET 4601 + 2%TiC) high strength alloy steels through powder metallurgy (P/M) technique has been under taken in the present research work. The green compacts of 0.5 aspect ratio (h/d) were sintered at 1100 ± 10 °C for 30 min in nitrogen purged electric muffle furnace. The sintered compacts were cold forged to obtain various densities of alloy steels preforms. Electrochemical and aqueous immersion corrosion tests were carried out on the cold forged alloy steels using pickling acid medium at various time periods. The experimental results show that the addition of TiC to the ATOMET 4601 decreases the corrosion rate of alloy steel and the corrosion rate is found to decrease with increase in density in the alloy steel compositions. Surface morphology, SEM, and XRD were also corroborated with the corrosion characteristics of the P/M alloy steels.

The Laser Deposited Nickel-Aluminum Bronze Coatings on SUS630 Stainless Steel and Its Corrosion Resistance in 3.5 wt.% NaCl Solution

In this work, three composite structures of nickel-aluminum bronze (NAB) bonded with SUS630 stainless steel with different intermediate layers were fabricated by laser deposition. The microstructure and corrosion behavior of NAB in 3.5 wt.% NaCl solution were studied. The NAB coating directly deposited on steel substrate contains a large number of Fe-rich dendrites due to the dilution by laser energy and the Cu-Fe liquid phase separation characteristics. The microstructures of NAB were independent and isolated well from the steel substrate when the nickel intermediate layer was applied. Immersion corrosion and electrochemical tests indicated that the composite structure with the nickel intermediate layer presented better corrosion resistance than direct deposited the NAB coating, especially with the NiCr alloy intermediate layer, which led to a shallower corrosion depth and formed a denser layer of protective corrosion products.

Robust corrosion performance of cold sprayed aluminide coating in ternary molten carbonate salt for concentrated solar power plants

In concentrated solar power (CSP) technology, high temperature corrosion is a key issue for material selection. In this context, a homogeneous and crack-free FeAl coating with high Al content was prepared by using cold spray (combined with a post heat treatment) to improve the corrosion resistance of stainless steel 316 L (SS316L) in molten carbonate salt for CSP applications. A series of immersion corrosion tests were performed to explore the corrosion behavior of the prepared aluminide coating in the LiNaK molten carbonate salt at 700 °C. The results demonstrated that the corrosion resistance of SS316L in the molten carbonate salt can be greatly improved by the prepared aluminide coating. This is attributed to the formation of a continuous dense LiAlO2 layer on the surface of the coating during corrosion. Although an α-LiAlO2 → γ-LiAlO2 phase transformation occurred during corrosion, it showed little influence on the corrosion performance of the prepared coating under the present experimental conditions. Furthermore, the coating remained intact even after 1000 h of corrosion. It is envisaged that the prepared coating has broad application prospects for CSP system with molten carbonate salt medium.

Microstructure-dependent crevice corrosion damage of implant materials CoCr28Mo6, TiAl6V4 and REX 734 under severe inflammatory conditions.

Fretting corrosion is associated with increased risk of premature implant failure. In this complex in vivo corrosion system, the contribution of static crevice corrosion of the joined metal alloys is still unknown. The aim of this study was to develop a methodology for testing crevice corrosion behavior that simulates the physiological conditions of modular taper junctions and to identify critical factors on corrosion susceptibility. Samples of medical grade CoCr28Mo6 cast and wrought alloy, TiAl6V4 wrought alloy and REX 734 stainless steel were prepared metallographically and the microstructure was investigated using scanning electron microscopy (SEM). Crevice formers that mimic typical geometries of taper junctions were developed. Crevice corrosion immersion tests were performed in different physiological fluids (bovine serum or phosphate buffered saline with additives of 30 mM H2 O2 at pH=1) for 4 weeks at 37°C. SEM with energy dispersive X-ray spectroscopy as well as focused ion beam were used to characterize the surface morphology, investigate present damages and identify the chemical composition of residues. Macroscopic inspection showed increased crevice corrosion susceptibility of TiAl6V4 and REX 734 under severe simulated inflammatory conditions. CoCr28Mo6 cast alloy exhibited degraded areas next to Cr- and Mo-rich precipitations that were located within the opposed crevices. The results indicate that aggressive electrolyte composition and crevice heights of 50-500 μm are critical influencing factors on crevice corrosion of biomedical alloys. Furthermore, manufacturing-related microstructure of common implant alloys determines the deterioration of corrosion resistance. The developed method should be used to enhance the corrosion resistance of common implant biomaterials by an adapted microstructure.

Effect of pH and Concentration on Electrochemical Corrosion Behavior of Aluminum Al-7075 T6 Alloy in NaCl Aqueous Environment

In the present study, the corrosion behavior of aluminum Al-7075 tempered (T-6 condition) alloy was evaluated by immersion testing and electrochemical testing in 1.75% and 3.5% NaCl environment at acidic, neutral and basic pH. The data obtained by both immersion tests and electrochemical corrosion tests (potentiodynamic polarization and electrochemical impedance spectroscopy tests) present that the corrosion rate of the alloy specimens is minimum for the pH=7 condition of the solution due to the formation of dense and well adherent thin protective oxide layer. Whereas the solutions with acidic and alkaline pH cause shift in the corrosion behavior of aluminum alloy to more active domains aggravated by the constant flux of acidic and alkaline ions (Cl− and OH−) in the media which anodically dissolve the Al matrix in comparison to precipitated intermetallic phases (cathodic in nature) formed due to T6 treatment. Consequently, the pitting behavior of the alloy, as observed by cyclic polarization tests, shifts to more active regions when pH of the solutions changes from neutral to alkaline environment due to localized dissolution of the matrix in alkaline environment that ingress by diffusion through the pores in the oxide film. Microscopic analysis also strengthens the results obtained by immersion corrosion testing and electrochemical corrosion testing as the study examines the corrosion behavior of this alloy under a systematic evaluation in marine environment.

Microstructure and corrosion resistance of AlCoCrFeNi high-entropy alloy coating on sintered NdFeB magnets prepared by HVOF spraying

AlCoCrFeNi high-entropy alloy (HEA) coating was formed on the surface of sintered NdFeB magnets by high-velocity oxygen-fuel (HVOF) spraying. The surface and fractured cross-sectional morphologies, phase composition and corrosion resistances of the coating were investigated using SEM, XRD, accelerated corrosion immersion test and electrochemical test, respectively. At the same time, the effect of AlCoCrFeNi coating on magnetic properties of NdFeB magnet was also studied. The results show that the surface of HEA coating exhibits the typical spraying morphologies, and the thickness is approximately 15 μm. The HEA coating is mainly composed of single BCC phase, and has little effect on the magnetic properties of the NdFeB magnet. In the sulfuric acid immersion test, few bubbles can be generated on the surface of the HEA coated sample after immersed for 300 min, and the weight loss is only 0.49 g/dm2, only 0.93 % of the uncoated sample. In the electrochemical test, the AlCoCrFeNi coated NdFeB sample also shows better corrosion resistance than the uncoated NdFeB sample. The present work provides a promising coating to improve the corrosion resistance of sintered NdFeB magnets.

Microstructures and corrosion behaviors of Al–6.5Si–0.45Mg–xSc casting alloy

The microstructures and corrosion behaviors of the Al–6.5Si–0.45Mg casting alloys with the addition of Sc were investigated by using scanning electron microscopy, X-ray diffraction, electrochemical measurement techniques and immersion corrosion tests and compared with those of Sr-modified alloy. The results show that Sc has evident refining and modifying effects on the primary α(Al) and the eutectic Si phase of the alloy, and the effects can be enhanced with the increase of Sc content. When the Sc content is increased to 0.58 wt.%, its modifying effect on the eutectic Si is almost same as that of Sr. Sc can improve the corrosion resistance of the test alloy in NaCl solution when compared with Sr, but the excessively high Sc content cannot further increase the corrosion resistance of the alloy. The corrosion of the alloys mainly occurs in the eutectic region of the alloy, and mostly the eutectic α(Al) is dissolved. This confirms that Si phase is more noble than α(Al) phase, and the galvanic couplings can be formed between the eutectic Si and α(Al) phases.

Effect of carbon addition on dissolution behavior of aluminum alloy sacrificial anode

Using potentiodynamic polarization and immersion corrosion and sacrificial anode material discharge performance testing methods studied the dissolution behavior of aluminum anode material in the working condition of simulated Northwest oilfield corrosion conditions. The research results show that carbon can reduce the corrosion potential of aluminum anode material and anode current density increase, which can improve the material corrosion dissolution performance. Immersion corrosion test results show that with the carbon content in ascension, to enhance the anode material of aluminum anode material of uniform dissolving ability, passivation phenomenon was significantly suppressed. Adding carbon anode materials to add up the uniform’s ability to dissolve, eliminate the phenomenon of local corrosion of anode material and the discharge efficiency is greatly increased, effectively solve the aluminum anode material in high temperature environment to serve the current efficiency degradation of field engineering problems.

Enhancing concrete sulfate resistance by adding NaCl

This study aimed to investigate the effects of adding NaCl on sulfate resistance of ordinary concrete. Concrete specimens were fabricated with 0.1%, 0.5%, and 1.0% NaCl (by weight of cement) and subjected to 10% Na2SO4 solution. The visual appearance of concrete was observed regularly. The compressive strength, ultrasonic velocity, and SO42− ion concentrations in concrete were also determined. Results indicated that incorporating NaCl in concrete can effectively inhibit the entry of external SO42− ions, consume the corrodible cement hydration products, and reduce corrosion product formation in concrete, thereby substantially enhancing the sulfate resistance of concrete. Under either full or partial immersion corrosion test, adding NaCl can reduce the compressive strength loss of concrete, lessen the development of concrete damaged layer thickness, and prevent the decline of concrete’s relative dynamic modulus. The sulfate resistance of concrete is approximately linear with NaCl content, particularly for concrete under partial immersion sulfate attack condition.

Macro-hardness and corrosion behavior of silicon carbide or boron carbide reinforced AA5052 MMC

Metal Matrix Composites (MMCs) enhance the mechanical and tribological properties according to the composition of the particulate reinforcement of Silicon Carbide (SiC) or Boron Carbide (B4C) and AA5052 aluminum alloy matrix. The MMC samples were fabricated by stir casting method of the liquid processing route. The same weight percentages (5 wt. %) and same particle size (63μm) of both SiC and B4C particulates are used to develop two different MMC samples. The hardness and corrosion tests were conducted to estimate the enhanced properties of the fabricated composites. The macro-hardness test and the immersion corrosion test were carried out by using a Vickers hardness tester at an applied load of 5kgf in accordance with ASTM E92 and a 3.5% NaCl solution in accordance with ASTM G31, respectively. With the help of optical microscopy, the corroded surfaces were analyzed. The results obtained from the investigation show that AA5052/B4C MMC gives better hardness and AA5052/SiC MMC shows higher corrosion rate compared to the other two samples.

A study on corrosion behaviour of various modes of ATIG welded plain carbon steel

The purpose of this study is to look at the corrosion behaviour of various current modes of Autogenous Tungsten Inert Gas (ATIG) welded powder metallurgy plain carbon steel (Fe-0.5% C). The impacts of different current modes (DC, AC, Mixed, and Pulsed) on ATIG corrosion welded joints are looked at. To get the highest density, the rectangular sintered plain carbon steel strips were subjected to a cold upset. The parent and welded specimens were subjected to aqueous immersion and electrochemical corrosion tests. The corrosion test findings were compared to the microhardness, corroded surface morphology, microstructure, and SEM of the corroded area. It is observed from the test results that as the parent metal contains pores could lead to a high corrosion rate and the ATIG welded specimens exhibit less corrosion rate due to pore free region at the weldment. The DC mode of the welded specimen is observed to exhibit a lesser corrosion rate compared to the other modes of welded specimens due to higher heat generation.

Microscopical and corrosion studies on Al6061 − 10% Al2O3 functionally graded metal matrix composites

The objective of this work is to manufacture Aluminium reinforced with 10 wt% Alumina Functionally Graded Metal Matrix Composite (Al6061 − 10 wt% Al2O3 FGMMC) through horizontal centrifugal casting process and to investigate its microstructural and corrosion properties. The microstructure was examined along the radial direction of the FGMMC and it indicated that the gradient arrangement of reinforcements across the radial direction with supreme alumina particles reinforcement at the outer periphery. Corrosion tests were carried out on the samples cut from the outer periphery of the FGMMC using an acidic immersion corrosion test. The influence of corrosion parameters such as 1 M acidic solution (Sulphuric, Hydrochloric and Nitric acid) and immersion time (0 to 220 h) on corrosion rate was analyzed. The result revealed that the reinforcement had no effect on the corrosion rate and also the samples immersed in the hydrochloric acidic solution showed higher corrosion rate in the early period of immersion time due to the presence of chloride ions.

The Corrosion Resistance and Mechanism of AT13/Fe-Based Amorphous Composite Coatings.

Due to high strength, high wear resistance and high corrosion resistance, the amorphous metallic glasses were investigated widely. In the present study, the corrosion resistance of amorphous coating and composite coatings with various proportions of AT13 (Al2O3–13 wt.% TiO2) ceramic as additions in 3.5 wt.% NaCl solution were studied. The corrosion resistance was improved obviously as the addition of AT13, and when the content of AT13 was 15 wt.%, the composite coating had the lowest corrosion current density (1.75 × 10−6 A cm−2) and the highest corrosion potential (−411 mV), which was 5.14 × 10−5 A cm−2 and −580 mV for Fe-based metallic glassy coating, respectively. The corrosion mechanism was proposed according to the long-time immersion corrosion test.

Biodegradable Zn–Sr alloys with enhanced mechanical and biocompatibility for biomedical applications

Zinc (Zn) is a new generation of biodegradable metal as temporary biomedical implants with a promising degradation rate. However, its clinical applications have been limited because of the insufficient mechanical properties. Considering the degradation property and biocompatibility, we proposed Zn–Sr alloys after extrusion treatments to simultaneously improve the mechanical strength and ductility. The in vitro and in vivo degradation and biocompatibility were also evaluated using electrochemical and immersion corrosion tests, various cell and bacterial models, together with subcutaneous and femoral implantations in rats. Results showed that the extruded Zn-0.7Sr alloys exhibited two times higher mechanical strengths (∼120 ​MPa) and better ductility (∼10%) than the pure Zn counterparts. The Zn–Sr alloys provided enhanced in vitro and in vivo biocompatibility along with promising antibacterial properties.

Microstructures and corrosion resistances of hypoeutectic Al-6.5Si-0.45 Mg casting alloy with addition of Sc and Zr

The microstructures and corrosion resistances of hypoeutectic Al-6.5Si-0.45 Mg casting alloys with addition of both Sc and Zr were investigated by using scanning electron microscope, X-ray diffraction, electrochemical measurement techniques and immersion corrosion tests. The results show that the addition of lower content of Sc has some modifying effect on the eutectic Si phases, but doesn't exhibit obvious refining action on the primary α (Al) phases of the alloy. The combined addition of both Sc and Zr can enhance the refining and modifying effects of Sc, and transform the primary α(Al) phases to equiaxed crystal, and the eutectic Si phases to the fine granular shapes. The corrosion resistance of the test alloys is firstly weakened, and then recovered, to some extent, with the increase of the exposure time in the 3.5 wt%NaCl solution. The test alloys with fine eutectic Si have poorer corrosion resistance than the test alloys with coarse eutectic Si. The formation of more galvanic couplings in the test alloys with fine eutectic Si is responsible for the poor corrosion resistance. The immersion corrosion rate of the test alloys with fine eutectic Si is higher than that of the test alloys with coarse eutectic Si. This is consistent with the results of the electrochemical corrosion studies. The corrosion of the alloys mainly occurs in the eutectic region, and the eutectic α(Al) phases are dissolved. It indicates that the Si phase is more noble than the α(Al) phase, and the galvanic couplings can be formed between the eutectic Si and α(Al) phases.

STUDY ON ALTERNATE IMMERSION CORROSION BEHAVIOR AND MECHANISM OF SDCM DIE STEEL FOR HOT STAMPING

In this paper, the alternate immersion corrosion test of Cr-Mo-V series SDCM steel for hot stamping was carried out, and different stresses were loaded with self-made fixture. The results shown that regardless of hardness and stress, the corrosion mode of the material is uniform corrosion. Stress could significantly increase the corrosion rate, with lower hardness and higher corrosion rate. Because of the existence of Corrosion Removal Layer (CRL), the maximum corrosion pit depth would be reduced. The maximum corrosion pit depth and Corrosion Pit density (CPD, ρv) were used to describe the degree of corrosion damage. From low to high hardness, the CPD ρv and corrosion resistance increased gradually. With the increased of tempering temperature, the hardness decreased, and the percentage of carbide area in the field of view increased from 16.36% to 24.32%. The irregular spherical carbide M23(C, N)6 rich in Cr coarsens and consumes Cr element in the material, which lead to the decrease of corrosion resistance. Through the polarization curve of the dynamic potential, we known that the current density was increased with the hardness decreased, from 28.53 μA/mm2 to 40.93 μA/mm2.

Corrosion Behavior of Corrosion-Resistant Spring Steel Used in High Speed Railway

Corrosion behavior of 60Si2Mn-A and 60Si2Mn-B in simulated industrial atmospheric environment was investigated by alternate immersion corrosion test and electrochemical method. The phase, morphology, characteristics of corrosion products, and the distribution of Cr, Cu, and Ni in the corrosion products of experimental steel were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe microanalyzer (EPMA). The results show that the phase of rust layer is Fe3O4 and γ-FeOOH in the early stage and then changes to α-FeOOH and γ-FeOOH in the later stage; the size of the rust layer with corrosion resistance of 60Si2Mn is less than 60Si2Mn; the Cr element accumulates in the rust layer of the experimental steel in the early stage of corrosion resistance; and Cu, Ni, and Cr in the corrosion resistance 60Si2Mn are concentrated in the rust layer near the substrate In the later stage of corrosion. As the corrosion cycle is prolonged, the corrosion potential and the resistance of the rust layer of the experimental steel increases, and the corrosion current decreases; in the same corrosion cycle, the corrosion potential and corrosion resistance of 60Si2Mn-B are greater than 60Si2Mn, and the corrosion current is less than 60Si2Mn.

Influence of dislocation on sour corrosion of carbon steel in a low H2S sour environment

AbstractThe influence of dislocation on corrosion of low alloy steel in a low H2S sour corrosion environment was investigated experimentally (immersion corrosion test and polarization measurement) and theoretically (ESM‐RISM simulation). The results showed that dislocation increases corrosion weight loss by promoting the anodic dissolution reaction. The Fe atom solubilities of two kinds of Fe slab models simulating conditions with/without lattice defects were evaluated, and the high Fe solubility of the model with lattice defects was clarified. Based on these experimental and theoretical findings, the mechanism by which dislocation influences anodic dissolution was discussed.