Corrosion Resistance Of Passive Film Research Articles

DFT study on Mo-stabilized passive films: Hydroxylation effects on chromium and iron oxide surfaces

Hydrous Cr2O3 and Fe2O3 surfaces without and with substitutional molybdenum were simulated by DFT modelling to investigate at the atomic scale the role of Mo in improving the corrosion resistance of passive films on stainless steels. The surface structures most energetically favoured were determined in the conditions of interest. For surfaces with a high degree of hydroxylation, the preferential location of substitutional Mo is just under the hydroxyl groups, in agreement with the experimental observations. The substitution by Mo is exothermic and Mo preferentially substitutes in Fe- than in Cr-rich zone of the inner barrier layer of passive films.

Effect of h-BN on corrosion behavior of nickel-copper alloy coatings prepared by high-speed laser cladding

Nickel-copper alloy is widely used because of its strong corrosion resistance in marine environment. There are great potentials to prepare NiCu alloy coatings on the surface of structural steel to replace cast NiCu alloys due to its high cost. High-speed laser cladding has characteristics of fast melting rate, low surface roughness, fine microstructure and low dilution ratio. However, nickel alloy coatings has the problem of solidification cracks. In this study, a series of composite coatings were prepared by using NiCu powders with different h-BN contents, then the effect of h-BN on structure and anti-corrosion of coatings was analyzed. The study shows that the structure of the NiCu composite alloy coatings was equiaxed crystals, columnar crystals and planar crystals from top to bottom portion. After adding h-BN, the coating had a lower oxygen vacancy mobility rate, resulted in the optimal corrosion resistance of passive film.

Study on corrosion resistance of passive film promoted by natural rosin-based passive sealant

An eco-friendly Rosin-based passive sealant is prepared, which can seal the micropores and repair the passive film in one-step. Sealing performance of sealants and the growth kinetics of the passive film were analyzed by 3D-XRT tomography, Electrochemistry and XPS. The results showed that the permeation depth of sealant reached more than 150 μm, and the natural rosin effectively prolonged the loss time of sealant. The phosphate conversion layer at the passive film/sealant interface changes the semiconductor properties of the passive film. After immersion for 360 h in 3.5 wt% NaCl solution, the amount of Fe2O3 and Cr2O3 in the passive film increased by 34 % and 20 %, respectively, and the film thickness increased by 257.9 %. Rosin-based passive sealant can directly inhibit the diffusion rate of defects in passive film. This study provides a new theoretical support for the application of rosin sealant.

Passive film and surface characterization of Alx(CoCrFeNi)100-x (x = 0, 5, 10, 15, 20) high entropy alloys

The current research on the corrosion resistance of high entropy alloys (HEAs), mainly focuses on the influence of element composition and percentage difference. Considering the almost consistent passivation range with different corrosion resistance contributed by element addition, it inevitably exists obvious differences the passive film properties. The effect of passive film on corrosion behavior of HEA is worthy to be investigated in detail. Considering the microstructure transformation detected by electron probe X-ray microanalysis (EPMA) and surface feedback effect measured by approach curve of scanning electrochemical microscopy (SECM), the passivity of Alx(CoCrFeNi)100-x (x = 0–20) HEAs in 0.5 M H2SO4 solution has been investigated by cyclic potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), Mott-Schottky analysis and X-ray photoelectron spectroscopy (XPS). The results demonstrate that the passive film is thick and dense at low Al content (5%), which shows excellent corrosion resistance. However, with the increase of Al content, the corrosion resistance of passive film deteriorates gradually. XPS are adopted to detect film composition to explain the reason of film property change. The results suggest that there are more oxidized states of Al and less oxidized states of Cr in the passive film of HEAs with Al addition. The dominate semiconductor characteristics of Alx(CoCrFeNi)100-x with Al addition change from p-type to n-type. All results indicate that the addition of Al has a significantly influence on the composition and properties of passive film on the Alx(CoCrFeNi)100-x alloys surface.

Crevice Corrosion of High-Grade Stainless Steels in Seawater: A Comparison Between Temperate and Tropical Locations

The corrosion risk for stainless steel components is not the same in all seawaters, with more failures generally reported in tropical seas. In this study, the influence of biofilm on electrochemical behavior and corrosion resistance of passive films of high-grade alloys was studied in different seawaters, including temperate seawater (France-Brest, North Atlantic Ocean), tropical seawater (Malaysia-Kelatan, Meridional China Sea), and intermediate conditions in terms of temperature (Brazil-Arraial do Cabo, South Atlantic Ocean). The stabilized open-circuit potentials and the polarization behavior of high-grade stainless steels were measured as a function of temperature in all of the tested field marine stations, providing quantified data and direct comparison of the biofilm-enhanced corrosion risks. Significant differences were measured in tropical and in temperate seawaters in heated conditions. Above 37°C, the biofilm activity was much more pronounced in tropical seawater compared to Atlantic Ocean sites, leading to much higher localized corrosion risk. Crevice corrosion of eight high-grades passive alloys was also studied with the use of crevice formers specifically developed for tube geometries. Duplex UNS S32205, superduplex UNS S32750, hyperduplex UNS S33207 and S32707, and 6Mo stainless steels UNS S31266 have been evaluated together with Ni-based alloys UNS N06845 and N06625. In the more severe conditions, the high-grade alloys UNS S32707 and the 6%Mo UNS S31266, both with pitting resistant equivalent number (PREN) around 50, showed better performance than commonly used superduplex UNS S32750 and UNS S39274 (PREN 40). The corrosion results are discussed regarding the monitored biofilm-induced depolarization measured in the different test conditions.

Evolution and corrosion resistance of passive film with polarization potential on Ti-5Al-5Mo-5V-1Fe-1Cr alloy in simulated marine environments

Evolution and corrosion resistance of passive film with anodic polarization potentials on Ti-5Al-5Mo-5 V-1Fe-1Cr alloy in a 3.5 wt% NaCl solution were investigated. The valence state of Ti element increased, while the passive film corrosion resistance exhibited an evolution trend from weak to strong and then to weak with increasing polarization potential. Adsorption energy calculations of Cl- indicated a stable adsorption of Cl- on the TiO2. Combined with the corrosion effect of corrosive ions on metal hydroxides, the passive film compactness would decrease and the roughness would increase, triggering a decrease in the passive film corrosion resistance as potential increased.

In-situ constructing and EDTA-enhancing of meta-aluminate passivation films on electroplated zinc surfaces

Hexavalent chromium is highly toxic and carcinogenic and is not permitted for passivation of zinc in many countries. Accordingly, the development of environmentally-friendly chromium-free passivation has received increasing attention. In this paper, the preparation of Zn2+ and Al3+ doped composite passivation films on electroplated zinc surfaces using meta-aluminates as passivator was studied, and it was found that the corrosion resistance of the passivation films could be effectively improved by using EDTA. As a complexing agent, EDTA can combine with many metal ions and form stable complexes. The mechanism of the passivator and the effects of passivator concentration, temperature, time, and pH on the passivation performance were investigated. The results showed that the corrosion current density (icorr) of the meta-aluminate passivation film reinforced with EDTA decreased to 2.068 × 10−7 A/cm2, which was better than the icorr of 1.524 × 10−6 A/cm2 without EDTA reinforcement and much smaller than the icorr of 2.376 × 10−5 A/cm2 without passivation. It can be seen that the strengthening effect of EDTA results in a compact passivation film on the surface of zinc metal. Furthermore. The corrosion resistance of meta-aluminate passivation film reached or approached the level of hexavalent chromium passivation film, which contributed to the chromium-free passivation of zinc.

Semiconducting Behaviour and Corrosion Resistance of Passive Film on Corrosion-Resistant Steel Rebars.

Chloride-induced corrosion of steel rebars is one of the major causes of the premature failures of reinforced concrete structures served in different environments. This paper investigates the semiconducting behaviour and corrosion resistance of the passive film formed on the corrosion-resistant rebars exposed to simulated concrete pore solutions with different pH values and chloride concentrations. The electronic properties of the passive film were studied using potentiodynamic measurements and capacitance measurements (Mott-Schottky analysis). The results indicate that, firstly, the passive film of corrosion-resistant steel rebar shows n-type semiconducting behaviour with shallow and deep donor states in the band gap during passivation, and the deep donor energy level of corrosion-resistant steel rebar passive film is not sensitive to the decreasing pH value; secondly, under the same conditions, the passive film of corrosion-resistant rebars has a larger negative flat-band potential and thicker space charge layer than hot-ribbed rebars; thirdly, n-type semi-conductivity at a higher potential disappears once the chloride concentration at the rebar surface attains the chloride threshold value; and finally, a reverse charge layer forms on the surface of CR rebar at 0.50 V potential.

Time Evolution of the Passivation Behavior of Ti-6Al-4V in 0.5 M Sulfuric Acid

The passivation behavior of Ti-6Al-4V alloy was studied by electrochemical and surface analyses, and a model was proposed to elucidate the connection between polarization time and properties of the passive film. Three stages of passive film growth can be divided based on the changes of current density during the formation process of passive film and the passive film grew and stabilized after polarized for 0 ∼ 2000 s under 1.0 V vs Ag/AgCl in 0.5 M H2SO4 solution. The chemical state of Ti at the topmost surface of passive film was independent of the polarization time, while the formation of oxides inside the passive film was promoted. The structure evolution of passive film was investigated by high-resolution XAS through the synchrotron radiation source. The formation and increase of thermodynamically stable rutile-TiO2 contributed to the enhancement of the impedance and corrosion resistance of passive film.

The effect of Nb content on microstructure and properties of laser cladding 316L SS coating

316L SS with different Nb content (0.2, 0.5, 1.0, 3.0, 5.0, 7.0 wt%) coatings were fabricated on Q235 steel plate by laser cladding. The addition of Nb made the phase structure of 316L change from FCC to FCC + BCC + Laves phase . With the Nb content increasing, the microhardness of 316L coating increased gradually. The Nb7.0 coating is about 2.0 times as hardness of the substrate. Electrochemical testing showed that Nb 1.0 coating had the best corrosion resistance in 3.5 wt% NaCl solution. Excess Nb will cause corrosion to occur more easily and decrease the corrosion resistance of the coating. • The compact 316L SS with dissimilar Nb alloy coating was prepared by laser cladding. • The Nb1.0 coating has good corrosion resistance in 3.5 wt% NaCl solution. • Niobium oxide played an important role in improving the corrosion resistance of passive film, but excessive niobium will have adverse effects on the structure. • The Nb7.0 coating has high microhardness.

Microstructure Evolution and Corrosion Behavior of Deformed Austenitic Stainless Steel Manufactured by Selective Laser Melting

The effect of room temperature deformation on the microstructure and corrosion behavior of selective laser-melted (SLM) 316L steel in 0.9 wt.% NaCl medium was explored by electrochemical tests, microstructural analysis, and passive film characterization. The irregular evolution of corrosion behavior was first found in the deformed SLM 316L steel. The corrosion resistance of SLM 316L steel improved with increasing room temperature deformation level reached the maximum at 20% deformation, and then weakened with further increasing deformation below 40%. Microstructural analysis indicated that the deformation twins passed through the molten pool boundaries when the deformation was 20%, but not when the deformation was 40%. The dislocation density, Σ3, and low-angle grain boundaries increased slightly with increasing deformation below 20%, but they increased distinctly with deformation level greater than 20%. Besides, room temperature deformation modified the oxide content of the surface passive film, especially for the chromium oxide, which affected the corrosion resistance of passive film. Above results indicate that low room temperature deformation level of SLM 316L stainless steel is feasible to improve its corrosion resistance and optimize the passive film.

Corrosion Resistance of Passive Film Formed on TA10 Dental Implant in Simulated Body Fluid

Corrosion Resistance of Passive Film Formed on TA10 Dental Implant in Simulated Body Fluid

The passive properties of TA10 in Coca-Cola containing oral environment

PurposeAt present, carbonated drinks such as cola are especially favored by the younger generation. But because of its acid, it often leads to tooth demineralization, resulting in “cola tooth”. However, the influence of cola on the corrosion resistance of passive film of TiA10 alloy restorative materials is rarely reported. The purpose of this study was to analysis the corrosion resistance, composition of the passive film of TA10 alloy in different concentrations of Cola.Design/methodology/approachThe passive behavior of TA10 alloy in artificial saliva (AS) and Cola was studied by means of potentiodynamic polarization, electrochemical impedance spectroscopy, cyclic voltammetry, Mott-Schottky techniques and combined with X-ray photoelectron spectroscopy and Auger electron spectroscopy (AES) surface analysis.FindingsWith the increase of cola content, the self-corrosion current density of the alloy increases sharply, and the corrosion resistance of the passive film is the best in AS, while Rp in cola is reduced to half of that in AS. The thickness of the passive film in AS, AS +cola and cola is about 9.5 nm, 7.5 nm and 6 nm, respectively. The passive film in cola has more defects and the carrier density is 1.55 times as high as that in AS. Cola can weaken the formation process of the protected oxide, promote the formation of high valence Ti-oxides and increase the content of Mo-oxides in the passive film.Originality/valueThese results have important guiding significance for the safe use of the alloy in the complex oral environments.

(Invited) Measurement of Passivation on Fe-6Cr Using an Ellipso-Microscope Combined with a Channel Flow Electrode Method

An electrochemical ellipso-microscopy cell was expanded by combination with a channel flow electrode method. Fe-6 wt% Cr was potentio-dynamically polarized to passive region in acidic 0.15 M Na2SO4 solution. During the polarization, the electrolyte solution was flowed at various flow rates under laminar flow condition, and the Fe-6Cr sample surface was monitored by the ellipso-microscope. Simultaneously, two detector electrodes in the solution downstream were potentio-statically polarized to detect Fe and Cr species dissolved from the sample. Dissolution rates of Fe and Cr species in active region were depended on the flow rate. When AES analysis was conducted after the polarization of Fe-6Cr, depth profiles revealed that Cr enrichment in the outermost layer of passive film. Cr ratio in metal cations on the passive film increased with increaseing in flow rate. These behaviors implied that the corrosion resistance of passive film formed under solution convection was improved by oxidized products generated in active region. In the presentation, Fe-6Cr anodic dissolution behavior and enrichment of Cr species are discussed.

Effects of Cl− and AC on the Corrosion Behavior of 2507 Super Duplex Stainless Steel in a Simulated Concrete Pore Solution

The effects of Cl− concentration and applied alternating current (AC) on the corrosion behavior of 2507 super duplex stainless steel (SDSS) were studied in a saturated Ca(OH)2 solution by electrochemical measurements, immersion test, and x-ray photoelectron spectroscopy. The results show that the presence of Cl− ions accelerates the corrosion of 2507 SDSS in the saturated Ca(OH)2 solution. The protective ability of passive film decreases as Cl− concentration increases, especially at the concentration of 10% Cl−. As the applied iAC increases, the ip value increases, and the Ep value decreases. The applied AC increases the number of defects within the passive film, affects the electronic property of the surface film, which results in a harmful effect on the passive film, and weakens its anti-corrosion property. The higher the iAC, the more severe the damage influence is. Moreover, imposed AC promotes the pitting corrosion sensitivity of SDSS and enhances its corrosion rate. The applied AC and the addition of Cl− exert a combined effect, reducing the corrosion resistance of passive film formed on 2507 SDSS.

Effects of different alloying elements M (M = Fe, Ni, Mn, Si, Mo, Cu, Y) on Cr2O3 with Cl: a first-principles study

Using the first-principles methods, the effects of different alloying elements M (M = Fe, Ni, Mn, Si, Mo, Cu, Y) on Cr2O3 with Cl adsorption are studied. The results show that the layer distance of all doped models has been widened to different degrees with Cl adsorption. When Mo or Y is doped into the passive film, the difference of layer distance is reduced to a certain extent. The interaction between alloying elements and Cl is studied by calculating the adsorption height, bond population and electron density difference. The results show that Mo and Y can inhibit Cl erosion and improve the corrosion resistance of passive film. Furthermore, we investigate the CrMoFe and CrMoY co-doped system with Cl adsorption. The calculations point out that when Mo and Y are doped together in the passive film, the corrosion resistance of the system is more prominent than that of CrMo, CrY and CrMoFe co-doping systems.

Corrosion resistance of passive films on different stainless steel grades in food and beverage industry

Passive films were grown on 304 L, 316 L and Duplex stainless steels by immersion at open circuit potential in solutions mimicking food and beverage industry environments. In acidic food stainless steel surfaces are covered by Cr rich passive films, and generalized dissolution occurs on their surface with consequent ions release into the electrolyte. In fatty food the concentration of released ions is significantly lower since generalized corrosion does not occur, but the loss on MnS inclusions strongly reduces the polarization resistance in this environment especially for 304 L due to its higher localized corrosion susceptibility with respect to the other grades.

Role of Coke in the Passive Properties of Vitallium 2000 CoCrMo Casting Alloy in Simulated Oral Environment

The passive behaviors of Vitallium 2000 CoCrMo casting alloy in artificial saliva (AS) and Coke were studied by potentiodynamic polarization, electrochemical impedance spectroscopy, cyclic voltammetry, Mott–Schottky combined with scanning electron microscopy, Auger electron spectroscopy, and x-ray photoelectron spectroscopy surface analysis. The results show that with the increasing content of Coke, the self-corrosion current density of alloy increased sharply, the passive film corrosion resistance showed the best in AS and worst in Coke, and the Rp in Coke is reduced to half of that in AS. The thickness of passive films in AS, AS + Coke, and Coke is about 4.5, 3, and 2.5 nm, respectively. Passive films all exhibit n-type semiconductors; with more defects, the carrier density in Coke is 2.3 times more than that in AS. The Coke inhibits the oxidation of Co, Cr, and Mo, and the Co/Cr rate and Cr6+ concentration within the passive film increase. Coke weakens the formation process of protected oxides, thus reducing the stability of alloy’s passive film.

Role of passive film in dominating the electrochemical corrosion behavior of FeCrMoCBY amorphous coating

FeCrMoCBY amorphous coating with a high volume fraction of amorphous phase (90%) was prepared on Q235 steel by atmospheric plasma spraying. Influence of passivation potential on the corrosion resistance of passive films on the coating surface was estimated by electrochemical measurements, capacitance analysis, AFM and XPS technique. The results revealed that increasing potential promoted the growth of a more compact and thicker film due to the formation of more bounded water and oxides. Reduction in hydroxides further decreased point defects density significantly in the passive layer when passivated at a higher potential. A low diffusivity (1.67 × 10−15 cm2 s−1) corresponding to point defects could suppress both the growth and degradation processes of passive film in chloride containing electrolyte, and thus enhance the film resistance to local thinning.

The Effect of Potential on Surface Characteristic and Corrosion Resistance of Commercial Pure Titanium Processed by Anodic Oxidation Treatment

Anodic oxidation treatment of commercial pure titanium was carried out at the voltage of 30, 50 V in 0.5 M H2SO4 solution so as to obtain the effects of the anodic potential on the surface characteristic and corrosion resistance of passive film. The morphology and corrosion resistance of the treated samples were investigated using scanning electron microscopy (SEM), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), potentiodynamic polarization curves and electrode impedance spectroscopy (EIS). The results show that increasing anodic potential can significantly enhance the corrosion resistance of commercial pure titanium.