Effect of alcohol on the corrosion of al alloys in 1 N H2SO4 solution Part I

The aim of this paper is to examine the effects of alcohol (1-buten-3-ol-l, 2-methyl-3-butyn-2-ol, 3-methyl-2-buten-1-ol, 3-methyl-3-buten-1-ol, 3-methyl-1-pentyn-3-ol, 5-hexen-1-ol) on the corrosion of Al alloys. The inhibiting effect of alcohol was investigated by electrochemical current-potential curves, atomic absorption spectrometry (AAS), metal microscopy,SEM and EDS. The results showed that alcohol (1-buten-3-ol, 2-methyl-3-butyn-2-ol, 3-methyl-2-buten-1-ol, 3-methyl-3-buten-1-ol, 3-methyl-1-pentyn-3-ol, 5-hexen-1-ol) had an inhibiting effect on the corrosion of aluminium alloys. Experimental results show that corrosion of alloys in H₂SO₄ solution have been effected by elements in alloys such as Cu, Zn, Mg and adsorption of alcohol on the surface of alloys in H₂SO₄ solution obeys Temkin adsorption isotherm. The use of alcohol in H₂SO₄ solution were shifted corrosion potentials (E_cor) to more negative values and acted as cathodic inhibitors on the aluminum alloys. EDS analysis of alloys displayed different intermetallic compounds on the surface of alloys, which might have changed the activity of alcohols depending on the surface morphology of alloys. This paper has showed that these alcohol inhibited corrosion of aluminium alloys in H₂SO₄ solution. The concentration of 20 mM alcohol was shown that above 90% inhibition was achieved, which is a rather high value.     

The effect of 3-methyl 1-pentyn 3-ol on the corrosion of Al-Si-Cu alloys in acid solutions by using SEM,EDX and AAS

In this study, the effect of alloying elements on the corrosion of Al-Si-Cu alloys in H₂SO₄ and HCl media content 3-methyl-1pentyn-3-ol (3mlp3ol) is investigated by using SEM, EDX, AAS. The effect of active elements and 3-methyl-1-pentyn-3-ol (inhibitor) on the corrosion of alloys is determined using SEM, EDX and AAS results. Experimental results which indicated active alloying elements are Cu, Zn, Mg for Al-Si-Cu alloys in the studied solutions. The article is published in the original.     

The effect of alcohol on the passivation of al alloys in 1 N H<Subscript>2</Subscript>SO<Subscript>4</Subscript> solution

In this study, the influence of different alcohol on the passivation of aluminium alloys have been investigated by using current-potential curves. Experimental results show that the addition of alcohol in H₂SO₄ solution have been changed passivation potential distance of the alloys. Elemental compositions of alloys have also directly affected passivation of alloys. This influence is more effective especially in alloys content higher Si also and less Cu.     

Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>-Deposit-Induced Corrosion of Mo-Containing Alloys

Disk alloys used in advanced gas turbine engines often contain significant amounts of Mo (2 wt% or greater), which is known to cause corrosion under Type I hot corrosion conditions (at temperatures around 900 °C) due to alloy-induced acidic fluxing. The corrosion resistance of several model and commercial Ni-based disk alloys with different amounts of Mo with and without Na₂SO₄ deposit was examined at 700 °C in air and in SO₂-containing atmospheres. When coated with Na₂SO₄ those alloys with 2 wt% or more Mo showed degradation products similar to those observed previously in Mo-containing alloys, which undergo alloy-induced acidic fluxing Type I hot corrosion even though the temperatures used in the present study were in the Type II hot corrosion range. Extensive degradation was observed even after exposure in air. The reason for the observed degradation is the formation of sodium molybdate. Transient molybdenum oxide reacts with the sodium sulfate deposit to form sodium molybdate which is molten at the temperature of study, i.e., 700 °C, and results in a highly acidic melt at the salt alloy interface. This provides a negative solubility gradient for the oxides of the alloying elements, which results in continuous fluxing of otherwise protective oxides.     

Corrosion and time dependent passivation of Al 5052 in the presence of H<Subscript>2</Subscript>O<Subscript>2</Subscript>

Corrosion and time–dependent oxide film growth on AA5052 Aluminum alloy in 0.25M Na₂SO₄ solution containing H₂O₂ was studied using electrochemical impedance spectroscopy, potentiodynamic polarization, chronoamperometric and open circuit potential monitoring. It was found that sequential addition of H₂O₂ provokes passivation of AA5052 which ultimately thickens the oxide film and brings slower corrosion rates for AA5052. H2O2 facilitates kinetics of oxide film growth on AA 5052 at 25° and 60 °C which is indicative of formation of a thick barrier film that leads to an increment in the charge transfer resistance. Pitting incubation time increases by introduction of H₂O₂ accompanied by lower pitting and smoother surface morphologies. At short exposure (up to 8 h) to H₂O₂–containing solution, the inductive response at low frequencies predominantly determined the corrosion mechanism of AA5052. On the other hand, at prolonged exposure times (more than 24 h) to 0.25M Na₂SO₄+1vol% H₂O₂ solution, thicker oxide layers resulted in the mixed inductive–Warburg elements in the spectra.     

Acid-acid function of Eichhornia crassipes roots as inhibitor for mild steel in 0.5 M H<Subscript>2</Subscript>SO<Subscript>4</Subscript> solution

The inhibitory potential of an acid extract of Eichhornia crassipes constituents on corrosion of mild steel in 0.5 M H₂SO₄ solution was the basis of this study. Acid extract of the root was employed to create the same type of environment for acidic cleaning and pickling. The roots of Eichhornia crassipes (water hyacinth) were sun-dried and pulverized into powdered form. Acid extraction was carried out by weighing 10 g of the pulverized roots into a beaker containing 1000 mL of 0.5 M H₂SO₄, placed in water bath at 90°C for 6 h and filtered the second day. The mild steel with a known weight was immersed inside the respective concentration of the blank and inhibitors (2–10% vol/vol) solutions at room temperature, after which it was retrieved and weighed at 1-day interval progressively for 12 days. A collection of compositional data was from AAS, FTIR. Polarization resistant, current density (I _corr), and corrosion potentials (E _corr) obtained from Methro Ohms Potentiostat. Phytochemical screening of the corrosion product was carried out using Spectrophotometer. Polarization calculation shows that the root acid extracts on mild steel have corrosion resistance potentials even after preserving it for 60 days.     

Electrochemical corrosion behaviors of amorphous Co<Subscript>69</Subscript>Fe<Subscript>4.5</Subscript>Ni<Subscript>1.5</Subscript>Si<Subscript>10</Subscript>B<Subscript>15</Subscript> alloy

The corrosion behavior of an amorphous Co₆₉Fe_4.5Ni_1.5Si₁₀B₁₅ alloy ribbon was examined as a function of solution temperature (15 °C to 55 °C) and pH (3 to 11). The results of potentiodynamic polarization tests in H2SO4 solution, NaCl solution, and HCl + NaOH solution at various levels of pH showed that the corrosion resistance for the alloy ribbon significantly deteriorated with increasing temperature and decreasing pH for given conditions. The Co₆₉Fe_4.5Ni_1.5Si₁₀B₁₅ alloy was actively dissolved in solutions at pH 3 to 9 but passivated in a solution at pH 11. By comparison of the corrosion behaviors of Co₆₉Fe_4.5(Nb,Cr,Ni)_1.5Si₁₀B₁₅ alloys in the solution at pH 11, Ni was considered to contribute less in improving the corrosion resistance of the alloy than did Cr and Nb.     

Residual protective effect of <Emphasis Type="Italic">o</Emphasis>-oxyazomethine derivatives against iron corrosion in 1 M H<Subscript>2</Subscript>SO<Subscript>4</Subscript> solution

The residual protective effect of n-component mixtures of o-oxyazomethine derivatives at the corrosion of iron in 1 M H₂SO₄ decreases with time and an increase in temperature of the environment and increases with an increase in the polarity of substituent groups in the molecules and the inhibitor concentration in the solution. These regularities are interpreted based on the principle of the linear free-energy relation.     

Oxidation Behavior of NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> Spinel-Coated Interconnects in Wet Air

Corrosion of boilers and heat exchangers is accelerated in the presence of vanadium, sodium, and sulfur from low-grade fuels. Several iron- and nickel-based alloys were immersed in 60 mol% V₂O₅–40Na₂SO₄ salt for 1000 h in order to investigate their degradation behavior at 600 °C in air. Materials performance was analyzed by means of substrate recession rate and metallographic characterization. Their corrosion mechanism is characterized by the formation of a sulfide/oxide layer adjacent to the metal, the dissolution of scale oxides in the molten deposit, and their precipitation near the outer surface of the deposit. High Ni- and Cr-containing alloys show the lowest metal loss rates. Al addition was detrimental due to low-melting eutectic AlVO₄–V₂O₅ formation. Fe–Cr-based alloys showed the highest metal loss rates. In such alloys, high Cr additions (above 20%) did not improve the performance due to the negative synergetic effect by simultaneous dissolution of Fe₂O₃ and Cr₂O₃. The predominant salt composition at the corrosion front varied from vanadate rich to sulfate rich during the exposure. This change in the attacking salt makes it difficult to find a protective material for mixed sulfate–vanadate-induced corrosion.     

Evaluation of in vitro and in vivo tests for surface-modified titanium by H<Subscript>2</Subscript>SO<Subscript>4</Subscript> and H<Subscript>2</Subscript>O<Subscript>2</Subscript> treatment

Titanium is widely used as an implant material for artificial teeth. Furthermore, various studies have examined surface treatment with respect to the formation of a fine passive film on the surface of commercial titanium and its alloys and to improve the bioactivity with bone. However, there is insufficient data about the biocompatibility of implant materials in the body. The purpose of this study was to examine whether surface modification affects the precipitation of apatite on titanium metal. Specimens were chemically washed for 2 min in a 1∶1∶1.5 (vol.%) mixture of 48 %HF, 60%HNO₃ and distilled water. The specimens were then chemically treated with a solution containing 97%H₂SO₄ and 30%H₂O₂ at the ratio of 1∶1 (vol.%) at 40°C for 1h, and subsequently heat-treated at 400°C for 1h. All the specimens were immersed in HBSS with pH 7.4 at 36.5°C for 15d, and the surface was examined with TF-XRD, SEM, EDX and XPS. In addition, specimens of commercial pure Ti, with and without surface treatment, were implanted in the abdominal connective tissue of mice for 28 d. Conventional aluminum and stainless steel 316L were also implanted for comparison. An amorphous titania gel layer was formed on the titanium surface after the titanium specimen was treated with a solution of H₂SO₄ and H₂O₂. The average roughness was 2.175 μm after chemical surface treatment. The amorphous titania was subsequently transformed into anatase by heat treatment at 400°C for 1h. The average thickness of the fibrous capsule surrounding the specimens implanted in the connective tissue was 47.1μm in the chemically treated Ti, and 52.2, 168.7 and 101.9μm, respectively, in the untreated commercial pure Ti, aluminum and stainless steel 316L.     

High-Temperature Exposure Studies of HVOF-Sprayed Cr<Subscript>3</Subscript>C<Subscript>2</Subscript>-25(NiCr)/(WC-Co) Coating

In this research, development of Cr₃C₂-25(NiCr) + 25%(WC-Co) composite coating was done and investigated. Cr₃C₂-25(NiCr) + 25%(WC-Co) composite powder [designated as HP2 powder] was prepared by mechanical mixing of [75Cr₃C₂-25(NiCr)] and [88WC-12Co] powders in the ratio of 75:25 by weight. The blended powders were used as feedstock to deposit composite coating on ASTM SA213-T22 substrate using High Velocity Oxy-Fuel (HVOF) spray process. High-temperature oxidation/corrosion behavior of the bare and coated boiler steels was investigated at 700 °C for 50 cycles in air, as well as, in Na₂SO₄-82%Fe₂(SO₄)₃ molten salt environment in the laboratory. Erosion-corrosion behavior was investigated in the actual boiler environment at 700 ± 10 °C under cyclic conditions for 1500 h. The weight-change technique was used to establish the kinetics of oxidation/corrosion/erosion-corrosion. X-ray diffraction, field emission-scanning electron microscopy/energy-dispersive spectroscopy (FE-SEM/EDS), and EDS elemental mapping techniques were used to analyze the exposed samples. The uncoated boiler steel suffered from a catastrophic degradation in the form of intense spalling of the scale in all the environments. The oxidation/corrosion/erosion-corrosion resistance of the HVOF-sprayed HP2 coating was found to be better in comparison with standalone Cr₃C₂-25(NiCr) coating. A simultaneous formation of protective phases might have contributed the best properties to the coating.     

Corrosion Behavior of Novel Al-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Composites in Aerated 3.5% Chloride Solution

The corrosion behavior of novel Al-Al₂O₃ MMCs was evaluated in aerated 3.5% NaCl solution through potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). These materials corrode almost spontaneously by pitting in aerated 3.5% NaCl solution. Observations indicate that intermetallic particles in these composites appear to play an important role in this pitting corrosion behavior. Addition of Al₂O₃ particles to the base alloys did not appear to increase their corrosion resistance significantly, although corrosion rate was affected by these reinforcement particles. In cyclic polarization experiments, the small difference between the pitting potentials and the repassivation potentials for these MMCs indicated their low resistance to pitting corrosion. EIS measurements indicate adsorption/diffusion phenomena at the interface of the composites. Electrically equivalent circuits are proposed to describe and substantiate the corrosion processes occurring in these materials.     

The role of Ce ions in electrochemical corrosion of 304 SS in Ce(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>.6H<Subscript>2</Subscript>O

Effects of temperature and potential on the electrochemical corrosion behavior of alloy AISI 304 (UNS S30400) Stainless steel were investigated in 3 wt.% cerium nitrate (Ce[NO₃]₃.6H₂O) solution. With an increase in electrolyte temperature from ambient temperature to 90°C, the corrosion potential of the alloy shifted towards the noble direction, and the resistance to polarization increased due to the formation of Ce-oxide on the electrode surface. The oxide films formed at the open circuit potential (OCP) and a passive potential of 0.4 V_SCE were examined by x-ray photoelectron spectroscopy (XPS). The oxide film formed at 50°C and a passive potentialof 0.4 V_SCE consists of mixed oxides of Ce and Cr, whereas that at OCP consists of only Cr oxide. The formation of Cr oxides on the electrode surface was primarily due to the nitrate (NO₃ ⁻) ions in Ce(NO₃)₃.6H₂O electrolyte.     

Chemical and phase composition of nanosized oxide and passive films on Ni-Cr alloys. II. XPS analysis of films produced by anodic passivation of alloys in 1 N H<Subscript>2</Subscript>SO<Subscript>4</Subscript>

XPS data of thin (1 to 2 nm) oxide films formed by the anodic passivation of Ni-2 at % Cr and Ni-6 at % Cr alloys in 1 N H₂SO₄ are discussed. Thermodynamic calculations of the solid-phase chemical reaction 3NiO + 2Cr = Cr₂O₃ + 3Ni are carried out taking into account the changes in the surface energy at the alloy-oxide film interface along with the Gibbs energy change in the alloy oxidation reaction.     

Electrodeposition of nickel-fullerene C<Subscript>60</Subscript> composition coatings

A method of preparing composition electrodeposits (CED) nickel-fullerene C₆₀ is proposed. The kinetics of electrodeposition of CED under potentiostatic conditions and the deposit structure are studied. It is shown that fullerene species are hydrogenated during the deposition. The corrosion and electrochemical behavior of CED in 0.5 M H₂SO₄ is studied.     

Die Korrosion von Kupfer-Aluminium-Legierungen in schwefelsaurer Beizlösung

Corrosion of copper-aluminium alloys in sulfuric acid containing pickling solutions Wrought copper aluminium alloys (aluminium contents between 5 and 10 weight-%, additions of Fe, Ni and Mn) have been studied by continous and alternating immersion tests in a solution containing 20% H₂SO₄ and 10% FeSO₄ at 40°C. In the as-extruded state the corrosion of monophasic alpha alloys increases with aluminium content. Larger quantities of ß' martensite exercise a negative effect. Addition of 2 weight-% Ni do not improve the corrosion resistance of the alloys with 5 and 8% Al. Cold reduction of alpha alloys give rise to a pronounced intensification of corrosion. No positive effect can be obtained by a thermal treatment of the alloys CuAl 10 Fe 4 Mn Ni and CuAl 10 Fe 4 Ni 5. The corrosion takes place under the following forms: uniform corrosion (CuAl 5), preferred corrosion of grain boundaries (CuAl*, Cual 9, Mn 2 FeNi and CuAl 10 Fe 4 Ni 5 after thermal treatment) and dealuminisation (CuAl 10 Fe 4 Mn 3 Ni). With a view to corrosion resistance the alloys CuAl 5, CuAl8 CuAl 9 Mn and - probably - CuAl 8 Fe seem to be superior to the others.     

Phase Diagram of the Quaternary Al(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>-Cu(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>-Zn(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>-H<Subscript>2</Subscript>O System

The phase diagram of the H₂O-Zn(NO₃)₂-Al(NO₃)₃-Cu(NO₃)₂ quaternary system at 30 °C has been established by using the conductivity measurements. The solid-liquid equilibria of the H₂O-Zn(NO₃)₂-Al(NO₃)₃, H₂O-Zn(NO₃)₂-Cu(NO₃)₂, H₂O-Al(NO₃)₃-Cu(NO₃)₂ ternary systems and two isoplethic sections were determined experimentally. The solid phases in equilibrium with the saturated solution are the tri- and hemipentahydrate of copper nitrate, the hexahydrate α and β of the zinc nitrate and the nonahydrate of aluminum nitrate. The copper and zinc nitrates are relatively soluble in opposition to the aluminum nitrate which presents some important precipitation domains.     

Corrosion of Inconel 690 in N<Subscript>2</Subscript>-0.1%H<Subscript>2</Subscript>S gas at 700-800 °C

Inconel 690 superalloy was corroded at 700 °C and 800 °C for up to 70 h in N₂-0.1% H₂S gas. It corroded almost linearly with large weight gains, displaying little protectiveness. Its corrosion rates were quite fast when compared with its corrosion in air or Ar-1%SO₂ gas. The formed scales were thick, fragile, and nonadherent. They consisted primarily of Cr₂O₃ with some NiCr₂O₄, Ni₃S₂, CrS, and Cr₂S₃. The H₂S gas accelerated the corrosion significantly by forming nonprotective sulfides and dissolving hydrogen in the scale and in the internal corrosion zone that consisted of discrete chromium-sulfides and some oxide particles. The marker test indicated that the scales grew by the outward diffusion of metallic ions such as Ni, Cr, Fe, and Mn, whilst the internal corrosion zone thickened by the inward migration of oxygen and sulfur through the lattice, grain boundaries, and microcracks.     

High temperature Corrosion behaviour of iron aluminides and iron-aluminium-chromium alloys

The high temperature corrosion of different iron aluminides and iron-aluminium-chromium alloys containing between 6 and 17 wt% aluminium, 2 and 10 wt% chromium and additions of mischmetal has been investigated in air as well as in carburising, chlorinating and sulphidising environments. It was found that all alloys showed excellent corrosion resistance to both oxidation in air and carburisation in CH₄/H₂ up to at least 1100°C and to sulphidation in SO₂/air up to at least 850°C. In these environments the corrosion behaviour is not influenced by the concentrations of aluminium and chromium. In oxygen deficient H₂S-atmospheres, however, the corrosion behaviour depends sensitively on the aluminium and chromium concentration. At least 12 wt% aluminium in chromium-free alloys or 10 wt% aluminium in alloys containing 10 wt% chromium are required to provide sulphidation resistance at 550°C. The chlorination resistance of iron-aluminium-chromium alloys is low due to their formation of volatile aluminium chlorides.     

Type II Hot Corrosion Screening Tests of a Cr<Subscript>2</Subscript>AlC MAX Phase Compound

Low-temperature hot corrosion tests were performed on bulk Cr₂AlC MAX phase compounds for the first time. This material is a known alumina-former with good oxidation and Type I high-temperature hot corrosion resistance. Unlike traditional (Ni,Co)CrAl alumina formers, it contains no Ni or Co that may react with Na₂SO₄ salt deposits needed to form corrosive mixed (Ni,Co)SO₄–Na₂SO₄ eutectic salts active in Type II hot corrosion. Cr₂AlC samples coated with 20K₂SO₄–80Na₂SO₄ salt were exposed to 300 ppm SO₂ at 700 °C for times up to 500 h. Weight change, recession, and cross-sectional microstructures identified some reactivity, but much reduced (<?1/10) compared to a Ni(Co) superalloy baseline material. Layered Al₂O₃/Cr₂O₃ scales were indicated, either separated by or intermixed with some retained salt. However, there was no conclusive indication of salt melting. Accelerated oxidation was proposed to explain the results, and coarse Cr₇C₃ impurities appeared to play a negative role. In contrast, the superalloy exhibited outer Ni(Co) oxide and inner Cr₂O₃ scales, with Cr–S layers at the interfaces. Massive spallation of the corrosion layers occurred repeatedly for the superalloy, but not at all for Cr₂AlC. This indicates some potential for Cr₂AlC as LTHC-resistant coatings for superalloys.