Static Immersion Corrosion Research Articles

Microstructure and static immersion corrosion behavior of AA7020-O Al plates joined by friction stir welding

In the present investigation, the influence of tool pin profile and postweld heat treatment on microstructure, hardness, and static immersion corrosion behavior of AA7020-O Al plates joined by friction stir welding was investigated. Friction stir welding was conducted using two tools having different pin profiles, typically, a tool with tapered cylindrical pin and a tool with two flat-sided cylindrical pin. Postweld heat treatment was carried out using a solution heat treatment temperature of 540 ± 1℃ for 12 h followed by aging at 155 ± 1℃ for 6 h. Corrosion tests were carried out by immersing the welds in an aqueous solution containing NaCl and H2O2 for 6 h according to ASTM-G110. The results revealed that the two flat-sided cylindrical pin tool produces finer α-Al grains, at the center of dynamically recrystallized zones, than the tapered cylindrical pin tool. The postweld heat treatment slightly increases the size of the α-Al grains at the center of dynamically recrystallized zones. In the as-welded conditions, the friction stir welded regions exhibited lower hardness values than the base alloy. However, the regions friction stir welded using two flat-sided cylindrical pin tool showed relatively higher hardness values than those regions friction stir welded using the tapered cylindrical pin tool. The postweld heat treatment slightly increases the hardness of the welded regions to values that are still lower than the base alloy. Generally, the dynamically recrystallized zones are more susceptible to corrosion than the base alloy. In both AW and postweld heat treatment conditions, the thermomechanically affected zones showed the lowest corrosion resistance when compared with dynamically recrystallized zones and heat affected zone regions. In the as-welded conditions, regions friction stir welded using tapered cylindrical pin tool exhibited better corrosion resistance than those friction stir welded using two flat-sided cylindrical pin. The postweld heat treatment improves the corrosion resistance of the dynamically recrystallized zones friction stir welded using two flat-sided cylindrical pin tool.

Influence of bath PH value on microstructure and corrosion resistance of phosphate chemical conversion coating on sintered Nd–Fe–B permanent magnets

The effect of bath PH value on formation, microstructure and corrosion resistance of the phosphate chemical conversion (PCC) coatings as well as the effect on the magnetic property of the magnets is investigated in this paper. The results show that the coating mass and thickness increase with the decrease of the bath PH value. Scanning electron microscopy observation demonstrates that the PCC coatings are in a blocky structure with different grain size. Transmission electron microscope and X-ray diffractometer tests reveal the coatings are polycomponent and are mainly composed of neodymium phosphate hydrate and praseodymium phosphate hydrate. The electrochemical analysis and static immersion corrosion test show the corrosion resistance of the PCC coatings prepared at bath PH value of 0.52 is worst. Afterwards the corrosion resistance increases first and then decreases with the increasing of the bath PH values. The magnetic properties of all the samples with PCC treatment are decreased. The biggest loss is occurred when the bath PH value is 0.52. Taken together, the optimum PH range of 1.00–1.50 for the phosphate solution has been determined.

The use of multiple pseudo-physiological solutions to simulate the degradation behavior of pure iron as a metallic resorbable implant: a surface-characterization study.

Understanding the interactions of a pure iron surface with biological elements, such as ions and proteins in an aqueous medium, is essential for an accurate in vitro assessment of corrosion patterns. In fact, the synergy of chlorides, carbonates, phosphates and complex organic molecules present in the body environment is a key factor affecting both in vivo and in vitro degradation of materials, especially iron and its alloys. The aim of this work was the assessment of degradation patterns of pure iron in 5 commercial pseudo-physiological solutions by a thorough study of degraded surface chemistry and morphology. It also provides a methodological basis to understand the short-term degradation mechanism of degradable iron depending on the surrounding physiological media. The standard static immersion corrosion test was modified to adapt the procedure to pseudo-physiological solutions. After a 14-day static immersion test, the surfaces of samples were investigated by scanning electron microscopy, stylus profilometry and atomic force microscopy techniques. The chemistry and phase composition of the degraded layers were evaluated, respectively, by X-ray photoelectron spectrometry and X-ray diffractometry. The morphology and composition of the degradation layers were found to be different for the test-solutions: for phosphate-rich solutions, the formation of an adherent passive layer was found; degradation mechanisms related to general corrosion were predominant for all the other solutions. In conclusion, the chemical composition of the used medium plays a fundamental role in the degradation pattern of pure iron, so that direct comparisons of solutions with different ion concentrations, as reported in the literature, need to be carefully assessed.

Microstructural and corrosion behavior of Al/SiC metal matrix composites

Several Al/SiC MMCs having several volume fractions up to 15vol.% and different SiC particulates average sizes, typically, 11, 6 and 3μm were fabricated using conventional powder metallurgy (PM) route. The effect of the size and volume fraction of SiC particulates on the microstructural and corrosion behavior of Al/SiC metal matrix composites (MMCs) were studied. The results revealed that the Al/SiC MMCs exhibited higher density than pure Al matrix. The static immersion corrosion tests of Al/SiC MMCs in 3.5wt.% NaCl aqueous solution at several temperatures showed that, at ambient temperature, the Al/SiC MMCs have better corrosion resistance than the pure Al matrix. Reducing the SiC particles size and/or increasing the volume fraction of the SiC particulates reduce(s) the corrosion rate of the Al/SiC MMCs. In contrast, the Al/SiC composites exhibited higher corrosion rates at 50°C and 75°C than the pure Al matrix.

Corrosion behavior of borided AISI 304 austenitic stainless steel

Purpose – The paper aims to clarify the effect of boriding on the corrosion behavior and mechanical properties of AISI 304 austenitic stainless steel. Design/methodology/approach – The commercially available steel was subjected to a boriding treatment with Ekabor III powders at temperatures of 1,223-1,273 K with boriding durations of 2-4 h. Microstructural characterization of the steel was carried out with optical microscopy, scanning electron microscopy and X-ray diffraction analyses. Static immersion corrosion tests were made using a 10 percent H2SO4 acid solution and salt spray tests were carried out in accord with the ASTM B-117 standard. Findings – Grain boundary precipitation of carbides was observed in the transition zone beneath the boride layers. The corrosion resistance of the steel against the acid solution increased to about seven times its untreated value with the boriding treatment. Research limitations/implications – The boride coating improved the corrosion resistance of the AISI 304 stainless steel against acidic media, but suffered from spalling in the salt spray test. Future work will focus on improving the adhesion between the coating and the substrate by changing the parameters for the boriding process. Practical implications – Pack boriding is a simple, environmentally friendly coating process and can be recommended for use in small and medium enterprises. The boride coatings deposited have potential in further improving the wear and corrosion resistance of stainless steels. Originality/value – The outcome of the research is of great importance for the industry using wear- and corrosion-resistant coatings.

Storage stability and corrosive character of stabilised biodiesel exposed to carbon and galvanised steels

The storage stability and corrosive character of soybean biodiesel stabilised with tert-butylhydroquinone (TBHQ) was investigated through static immersion corrosion tests. Coupons of carbon steel and galvanised steel were immersed in soybean biodiesel with and without TBHQ for 12weeks. Measurements of total acid number, peroxide value, oxidation stability (Rancimat induction period), metal release, and TBHQ consumption at different stages of corrosion were performed. After 12weeks of the static immersion test with both steels, the non-stabilised biodiesels presented induction times below the EN 14214 limit (6h); these results were in agreement with increase in the peroxide values. Zinc release was only detected in the non-stabilised biodiesel exposed to galvanised steel, whilst iron was not detected in any biodiesel samples exposed to carbon steel. The absence of zinc in the TBHQ-doped biodiesel exposed to galvanised steel indicates that TBHQ may have acted as a corrosion inhibitor. Additionally, TBHQ was rapidly consumed in the first 3days of experiments, providing evidence of its activity. For a storage period of up to 56days, both galvanised and carbon steels were shown to be compatible with biodiesel even in the absence of an antioxidant. The presence of zinc (>2μgg−1 after 28days of immersion) due to corrosion did not promote biodiesel deterioration.

Corrosion behaviour of Al/SiC and Al/Al2O3 nanocomposites

In the present investigation, the static immersion corrosion behavior of Al/Al2O3 and Al/SiC nanocomposites in 1 M HCl acidic solution was evaluated. The nanocomposites were fabricated using conventional powder metallurgy (P/M) route. The effect of nanoparticulates size and volume fraction on the corrosion behavior of nanocomposites was studied. The durations of the corrosion tests ranged from 24 to 120 hours and the temperatures of the solution ranged from ambient to 75 oC. The corrosion rates of the nanocomposites were calculated using the weight loss method. The results showed that both Al/SiC and Al/Al2O3 MMNCs have lower corrosion rates than the pure Al matrix. Such behavior was noticed at both ambient and higher temperatures. Generally, the Al/Al2O3 nanocomposites exhibited lower corrosion rates than the Al/SiC nanocomposites. The Al/Al2O3 (60 nm) nanocomposites exhibited the highest corrosion resistance among all the investigated nanocomposites. The corrosion rate was found to be reduced by increasing of the exposure time and the volume fraction of the nanoparticulates, while it was found to be increased by increasing of the nanoparticulates size and the solution temperature.

Effect of III-Pass on Microstructure, Micro Hardness and Static Immersion Corrosion Resistance of AA6061-T6/SiCp Surface Composite Fabricated by Friction Stir Processing

In this current investigation, SiC particles 20μm in average size were incorporated into the commercially AA6061-T6 to prepare surface composite by using Friction stir processing (FSP). The morphology of the reinforcement inside the Al matrix has been evaluated from scanning electron microscope (SEM) and the corrosion characteristics of the resulted composite were evaluated using static immersion corrosion (SIC) behavior in 3.5% NaCl aqueous solution at various regimes. From the results, it observed that the SiC particles were distributed uniformly inside the stir zone (SZ) in both first and third-pass of FSP. The micro hardness of stir zone with SiC particles of I-pass was higher compared to III-pass and as-received Al alloy. In static immersion corrosion test the FSP AA6061-T6/SiCp exhibited significantly greater corrosion resistance in I-pass than compared to the III-pass and as-received Al alloy.

Dry Sliding Wear And Static Immersion Corrosion Resistance of Aluminum Alloy 6061-T6/SiCp Metal Matrix Composite Prepared Via Friction Stir Processing

In this experiment, SiC particles 20μm in average size were incorporated into the commercially Aluminum alloy 6061-T6 to form particulate metal matrix composite produced by using Friction Stir Processing (FSP). After the preparation of composite, the homogeneity of the particles distribution inside Al matrix has been observed by optical microscope (OM) and scanning electron microscope (SEM). Dry sliding wear test was conducted by using pin on disk equipment and Static immersion corrosion (SIC) resistance was evaluated in 3.5% NaCl aqueous solution at various regimes. From the results, it observed that the SiC particles are well distributed homogenously inside the nugget zone without any defects, obtained good bonding between the SiC particles and Al matrix alloy. The micro hardness of nugget zone with SiC particles is more compare to the as-received Al alloy due to the dispersion of SiC particles. It found that, exhibited superior dry sliding wear resistance and significant improvement SIC resistance of FSPed Aluminum alloy 6061-T6/SiCp composite is compare with as-received Al alloy.

Behaviour of the antioxidant tert-butylhydroquinone on the storage stability and corrosive character of biodiesel

The behaviour of the antioxidant tert-butylhydroquinone (TBHQ) on the storage stability of biodiesel was investigated. Storage conditions were simulated through static immersion corrosion tests in biodiesel (with and without TBHQ) using copper coupons. Measurements of oxidation stability (Rancimat induction period) and metal release at different stages of corrosion were performed. After 24h of the static immersion test, the neat and TBHQ-doped biodiesels presented induction times below the EN 14214 limit (6h). Copper release was more intense in the neat biodiesel which evidenced that TBHQ retarded the corrosion process as a corrosion inhibitor. Ion trap–time-of-flight mass spectrometry (IT–TOF-MS) revealed the presence of considerable amounts of tert-butylquinone (TBQ) in the TBHQ-doped biodiesel exposed to the corrosion process. As TBHQ molecules adsorb at the copper surface to inhibit corrosion, these molecules are catalytically oxidised to TBQ. IT–TOF-MS also indicated the formation of new molecules of high molecular weight only presented in the TBHQ-doped biodiesel deteriorated by the corrosion process. MS2 spectra gave clear evidence of the formation of new complexes between free radicals of long-chain molecules (fatty acid derivatives) and TBQ radicals during biodiesel deterioration.

The Influence of Deformation on Dechromization Corrosion of CuCr Alloy in H<sub>3</sub>PO<sub>4</sub> Solutions

The influence of deformation on dechromization of CuCr alloy in H3PO4 solutions was investigated by static immersion corrosion tests. The properties of undeformed and deformed alloys were characterised by XRD, Metallograph, SEM and X-ray fluorescence spectrometer respectively. It is observed that the deformation plays an important role in dechromization of CuCr alloys in H3PO4 solutions. Compared with undeformed one, the deformed CuCr alloy’s incubation time of corrosion is shortened, the concentration and temperature of H3PO4 solutions needed for dechromization decrease. Consequently the tendency of dechromization increases. Surface analysis showed that the microstructure of the dechromization layer is scarcely influenced. Finally, the dechromisation mechanism was discussed.

Farklı ısıl işlem koşullarındaki 2024 aluminyum alaşımlarının korozyon sonrası mekanik özelliklerindeki kaybın belirlenmesi

In this study, the solution treatment of all 2024 Al-alloys was conducted at 510°C for 2,5 hour. Then, the solution heat-treated 2024 Al-alloys were subjected to the various heat treatments which are W, T4, T6 (100 o C-10h), T6 (190 o C-10h) and O temper conditions. The microstructure of the alloys were examined by opti- cal and scanning electron microscopy (SEM). Static immersion corrosion tests for the tensile samples were carried out in a 3.5 wt. % NaCl solution for 2 months, open to air, at room temperature. The tensile tests of the specimens were carried out before and after corrosion. The results obtained were compared and the losses occur- ring in the strength and elongation after corrosion were determined. The minimum loss was observed in T4 heat treatment while the maximum loss was occurred in W heat treatment.

Corrosion properties of friction–stir processed cast NiAl bronze

Friction–stir processing (FSP) was adopted to modify the microstructure of a cast Cu–9Al–4.5Ni–4Fe NiAl bronze alloy (NAB). After FSP, the initial coarse microstructure of the cast NAB was transformed to a fine structure, and the porosity defects were eliminated. The microstructure modification changed the corrosion behavior of the NAB in a 3.5% NaCl solution. In a static immersion corrosion test, the FSP NAB exhibited significantly greater corrosion resistance compared to the cast counterpart. The polarization curve and electrochemical impedance spectroscopic (EIS) results indicated that the FSP NAB showed slightly lower electrochemical corrosion resistance.

Corrosion resistance in different environments and structural features of dental casting alloys for resin bonding

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ChemInform Abstract: The Corrosion of Aluminum in Sodium Polysulfides and Sulfur at 350 °C.

AbstractThe results of static immersion corrosion tests in various polysulfides (i.e., Na2S3, Na2S4, Na2S5) and sulfur show that Al is not compatible with the discharged state of the positive electrode of the sodium/sulfur cell and that the corrosion product in sulfur is only Al3S3.