Papers by Keyword: Corrosion

Abstract: A layered clay/epoxy coating was fabricated to investigate the effects of montmorillonite (MMT) and halloysite nanotube (HNT) loading at 0.5, 1.5, and 2.5 parts per hundred resin (phr) on the corrosion resistance and thermal stability of coated mild steel plates. The corrosion study was carried out by Electrochemical Impedance Spectroscopy (EIS) and Tafel polarization. The |Z|_0.1Hz value, R_ct, and R_p of the layered/clay epoxy coatings containing 1.5 phr of HNT and MMT exhibited the best anticorrosion performance compared to other clay content levels. The |Z|_0.1Hz value for the epoxy coating filled with 1.5 phr of MMT (M1.5) is 2.132 × 10⁹ Ω·cm², while it is slightly higher for H1.5 coatings, i.e., 2.629 × 10⁹ Ω·cm². Water absorption trends were consistent with EIS and Tafel polarization studies. The presence of highly compatible nanocontainers clay reduced the total free volume and promoted cross-linking, enhancing anticorrosion performance. Thermal Gravimetry Analysis (TGA) showed that a 1.5 phr loading of MMT in layered/clay epoxy coating demonstrated better thermal stability than a coating embedded with HNT. This improvement can be attributed to the barrier effect of MMT, which retards the diffusion of oxygen molecules into the coating.

Abstract: Aluminum materials are used in a wide field for household appliances, aircraft, cars, ships, and construction. This research aims to obtain a new material based on aluminum magnesium silicon (AlMgSi) alloy as an alternative material to replace the steel base material in the shaft propeller product. In this paper, we will use the die-casting method to investigate corrosion resistance and the microstructure of the propeller shaft with AlMgSi aluminum alloy base material. The main base material used is 6063 aluminum alloy, with variations in the addition of Si (1, 2, 4 wt%). Alloy Al6063 is heated to a temperature of 720°C to reach a complete liquid state. Then the temperature is lowered to 645°C, then the Si element is inserted into the heating furnace and stirred. Then the temperature is lowered to 615°C, then the Mg element is added, then stirred thoroughly by a mechanical stirrer. The rotational speed of the stirrer is 70 rpm and the stirring time is 240 seconds. They were then heated to a pouring temperature of 680°C. The mold is heated to a temperature of 265°C. Then poured into the mold and pressed 7 MPa. The cast is cooled at room temperature. Then the casting products were heat treated with a solution treatment temperature of 485°C for 3600 seconds and quenched. After that, the casting products were treated with artificial aging. The results of this study show corrosion resistance increases along with the addition of variations of Silicon. The highest corrosion rate was obtained by adding Si as much as 4 wt% of 511.28 mm/y. With the addition of variations of Silicon 0 wt%, 1 wt% and 2 wt% showed the corrosion rate of 173.35 mm/y, 201.60 mm/y, 233.49 mm/y. The microstructure shows differences in grain structure. materials with variations of si 0 wt% and materials with variations of si 0 wt%, 1 wt%, 2 wt% and 4 wt% have different grain sizes. The intermediate phase (Mg₂Si) was mostly formed at Si 4% wt variation. So this study proves that adding silicon elements can increase grain sizes and refiner the propeller shaft.

Abstract: It is natural to define marine corrosion in terms of the different zones in which the corrosion occurs such as atmosphere splash, tidal and sea mud etc. However, this study focused on issues affecting the marine structures, different types of corrosion and their impact on the marine steel structures as well as the machinery/equipment. Furthermore, several control measures of corrosion necessary to avert corrosion in marine environments were discussed. However, it was established that prolonged contact of marine structures with seawater would lead to corrosion as well as ruing the safety elements present. Thus, the study provides potential information to material scientists on the need for using structural steels of adequate mechanical properties.

Abstract: In this study, the corrosion behavior of aluminum alloy was investigated in graphene nanoplatelet (GNP) nanofluids prepared with different surfactants. The surfactants include sodium dodecylbenzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), Tween 80, and Gum Arabic (GA). The corrosion properties of the alloy in the different GNP nanofluids were evaluated using potentiodynamic polarization tests at room temperature. The surface morphology of the aluminum alloy was analyzed using a scanning electron microscope coupled with an electron dispersive spectroscopy detector. The experimental results revealed that the addition of surfactants improves the resistance of the aluminum alloy to corrosion in the nanofluid. This was attributed to the adsorption of surfactants on the surface of the alloy to form a protective film layer, which reduces moisture permeability and enhances corrosion inhibition. The addition of GA was found to exhibit the highest inhibition efficiency. This was followed by Tween 80, SDS, and SDBS, which contributes the least inhibition. XRD post-corrosion analysis also reveals the presence of aluminum oxide and aluminum hydroxide phases on the surface of electrodes immersed in all the different GNP nanofluids.

Abstract: Siliconizing is one of the case-hardening processes used in the enhancement of some carbon-steel based material properties. Gears, rolling engineering parts, and pickling tanks produced with mild steel can offer better wear and hot-corrosion resistance characteristics through siliconizing. However, the cost of silicon hindered the wide usage of siliconized mild steel, which is the motivation for seeking remedy through processing of agro-waste materials. In this work, waste rice husk was used in the production of silicon nanoparticles using the sol-gel method. The silicon nanoparticles produced were used in the siliconizing of mild steel. The microstructure, hardness values, wear and corrosion tests were determined. The work shows that enhanced hardness values with improved corrosion and wear resistance were obtained when using waste rice husk to siliconize mild steel that can be used in the production of gears and storage tanks.

Abstract: Pipes from industrial process flow diagrams have a predictable risk of failure or damage, so that periodic inspections are carried out. Corrosion that occurs in the pipe can cause a risk of leakage or blockage of the pipe flow which can be fatal to the fluid distribution process. This damage can be anticipated by inhibitors adding and predicting the corrosion rate. This research was conducted to determine the effective concentration of Na₂CrO₄ inhibitor to inhibit the corrosion rate and predict the lifetime of the furnace cooling water circulation pipe using the weight loss method. Na₂CrO₄ inhibitor is a type of anodic inhibitor that works by passively the anode by inhibiting corrosion on a whole metal surface. The study begins with the preparation stage, cutting the pipe into specimens of a certain size, smoothing the surface and weighing the initial weight. The testing phase was carried out by immersing the specimens at various times of 120 h, 240 h and 360 h with Na₂CrO₄ inhibitor variations concentration was 0%; 0,3%; 0,6%; and 0,9%. The corrosion rate was calculated by re-weighing the specimen after the immersion process. The results showed that the most effective inhibitor concentration was 0.6% with a corrosion rate of 0.3021 mmpy and the Remaining Service Lifetime (RSL) was 9.399 years.

Abstract: Dissimilar aluminum butt joints were successfully joined using a friction stir welding machine, employing four welding speeds (50, 60, 70, 80 mm/min), four rotational speeds (900, 1000, 1100, 1200 rpm), and four different weld tool profiles (T1=12/4, T2=15/5, T3=16/4, T4=20/5 in D/d ratio). The corrosion analysis suggests that specimens 9, 10, 11, and 13 exhibit higher corrosion resistance, with a breaking potential of -0.6 eV, while specimen 8 shows the lowest corrosion resistance with a breaking potential of -2.1 eV. The results from the differential scanning calorimeter illustrate the formation of precipitation dissolution due to high heat generation at the nugget zone. An eddy current defect detector experiment was conducted to detect surface flaws in the welded samples. Few surface cracks were observed in the T2 profile specimens, which have a larger contact region or shoulder diameter, while more surface cracks were observed in the T1 profile samples.

Abstract: The purpose of this research is to use an electrochemical method to evaluate corrosion conditions of steel bars in concrete. According to the description of ASTM C876, when the corrosion potential measurement values of the steel bar are below -350 mV, there may be a greater than 90 percent chance of corrosion. If the current impedance of the concrete is below 10 kΩ-cm, there is a possibility of corrosion in the steel bar. The test plan is as follows: to use concrete with different concentrations of chloride ions or applying an electric current to the steel bars to accelerate the corrosion reaction. In addition, we plan to use a solution of chloride ions to simulate sea tidal erosion on reinforced concrete structures by spraying. According to the experimental observations, concrete containing chloride ions is very likely to cause internal corrosion of the steel bar. The current impedance of the concrete can be used as the basis for assessing the internal humidity and moisture content of concrete. With an increase in curing time, the concrete's resistance correspondingly increases.

Abstract: A novel Zn biodegradable composite was produced by direct extrusion of Zn powders at room temperature. The powders were efficiently consolidated to a high relative density, and the composite reached a UTS higher than 120 MPa and elongation of almost 70%. Microstructural observations showed ultra-fine Zn grains decorated by well-dispersed ZnO clusters at the grain boundaries. The degradation behavior of the composite and an as-cast Zn reference accessed by immersion tests in HBSS for both materials were similar and gave an equivalent corrosion rate. Additional static immersion tests in DMEM + 5% FSB showed a similar corrosion rate (0.015 mm/y), but SEM analysis of the corroded surface suggested that the degradation process of each as-cast or DE consolidated composite differs. MTT assays with extracts of both as-cast and extruded composites showed similar cytotoxicity, which was dependent on the dilution of the extracts. It was concluded that the proposed methodology brings the potential for an interesting solution to produce a sound Zn-ZnO composite with good biocompatibility, satisfactory corrosion rate, and high yield strength.

Abstract: This work focuses on the issue of corrosion and durability of mortar mixtures in aggressive environment. The intention was to find out and compare the impact of replacements on the durability of cement mortar exposed to an aggressive environment by comparison of various substitutes for cement, which are currently not widely used for this purpose with the commonly used ones.