Papers by Keyword: Corrosion

Abstract: The development of effective localized corrosion damage prediction methods is essential for the successful avoidance of unscheduled downtime in steam turbines. It is reported that damage in steam turbines initiates in highly localized areas, most commonly at corrosion pits that act as stress raisers. Therefore, the evaluation of pits distribution and depth is necessary.

Abstract: A double-layer composite coating on Q235 steel substrate was prepared using a new developed in situ technology consisting of SHS reaction, laser cladding and metal dusting techniques. A double-layer composite coating consists of the TiO₂–TiC ceramic outer layer and the TiC-CNTs cermet inner layer. An excellent bonding was observed among the outer layer, the inner layer and the steel substrate. Corrosion behavior of the coating was investigated and the commercial 304SS was used for comparison. The outer layer exhibited the highest corrosion resistance and 304SS the lowest corrosion resistance, whereas the inner coating exhibited the intermediate corrosion resistance. However, the severe pitting corrosion which was observed in 304SS did not exist for the coating.

Abstract: Reinforcement corrosion is one of the main causes of concrete deterioration. The steel in concrete is naturally protected from corrosion by the presence of a passive film formed through the high alkalinity of concrete. A technique to improve the protection of steel in concrete is the inclusion of mineral additions. Natural pozzolan (NP) from Beni-Saf is a mineral addition that is abundant in western Algeria. The experiment was conducted on mortar specimens, containing steel bars and exposed to the aggressive solutions of Na₂SO₄ and MgSO₄. The status of reinforcement is periodically monitored by measuring the electrochemical potentials and the corrosion rates by the technique of linear polarization resistance (LPR) and also the thermal conductivity was evaluated. The test results show that natural pozzolan significantly affects the physical properties of mortars, improves the corrosion resistance of mortars containing up to 20% of natural pozzolan and reduces the thermal conductivity.

Abstract: Tomatoes (Lycopersicon esculentum), is a fleshy berry regarded as very popular perishable fruit as well as vegetable grown throughout the tropical and temperate regions of the world. This research work investigated the effect of tomato juice on the electrochemical properties of brass, galvanized and stainless steel using potentiostatic polarization method and weight loss technique at room temperature. The samples were cut into sizes, 2 cm by 2 cm for galvanized and stainless steel, while brass a cylindrical shape of 2.5 mm diameter was cut into 5 cm height, the cut metallic samples was weighed using a sensitive weighing balance and recorded. The pH of the tomato juice was measured and the cut metallic samples were immersed into the containers filled with tomato juice and exposed for a period of 30 days. Weight losses of samples and pH of the tomato juice were determined at an interval of 5 days and the corrosion rates were evaluated. The results showed that brass and stainless steel had very low corrosion rates which decreased with time. High corrosion attack was observed on the galvanized steel and this is shown by the high corrosion current density and corrosion rate obtained on the polarization curve showing active corrosion reaction properties. The pH of the tomato progressed to neutrality within five days and to alkalinity at the end of the thirty days test for galvanized steel while the pH of the tomato juice was less acidic at the end of the thirty days test for both brass and stainless steel. Stainless steel was confirmed as best storage material for tomato juice in this study.Keywords: Corrosion, electrochemical, potentiostatic polarization, weight loss, tomato, metal

Abstract: The purpose of carried out examination was to determine the effect of solution heat treatment on the structure and corrosion resistance of the ZnAl40Cu3 alloy in the "acid rain" environment. The scope of the test included Brinell hardness tests, structural tests and galvanostatic and potentiodynamic tests. The examination showed that the maximum hardness of the sample after solution heat treatment obtain after 10 h of solutionizing. It has been shown that the solutionizing increases the corrosion resistance. The corrosion resistance was greater, when the longer was the time of solutionizing.

Abstract: The purpose of the examination was to determine the corrosion resistance of ZnAl40Cu(1-2)Ti(1-2) alloys in an "acid rain". Subject of test were ZnAl40Cu2Ti, ZnAl40Ti2Cu1.5Ti1.5 and ZnAl40Ti2Cu alloys. The scope of the test included galvanostatic, potentiodynamic tests and examination of the surface of the samples after corrosion. It was found, that the ZnAl40Cu2Ti alloy is characterized by the highest corrosion resistance among the tested alloys. Tests have shown that with a decrease in copper content in the tested alloys decreases corrosion resistance. It was also found that the corrosion of alloys tested in an "acid rain" is local.

Abstract: This paper summarizes different types of degradation of concrete in the energy industry. There is described the most of important kinds of degradation and what effects they can cause. In conclusion, this article is formulated several points to prevent the degradation of building materials.

Abstract: The purpose of this research is to study the properties of geopolymer paste based on metakaolin and rice husk ash (RHA) as coating material. Geopolymer paste was produced through alkaline activation method added with rice husk ash as much as 15% relative to the mass of metakaolin. The coating was achieved by painting the substrates with geopolymer paste. The coated material were cured at 60 °C for 3 hours. Samples were left at room temperature until seven days before any testing was conducted. The chemical resistance of the sample was studied by immersing the samples into (H₂SO₄) 1% for three days and it was found that the coated material was still in good condition. The presence of RHA was found to improve the thermal properties of geopolymer paste. The results showed that geoplymer paste was an excellent coating material for chemical and fire protection.

Abstract: Corrosion resistance performance of Sn-3.0Ag-0.5Cu (SAC305) was evaluated in 1 M hydrochloride acid through potentiodynamic polarization. SAC305 shows active-passive corrosion behavior in acidic solution with two dissolution peaks detected in anodic branch. Microstructure analysis revealed that the corrosion product deposited on the surface after polarization was porous and uneven. This limits the protection offered by the passivation film as the porous structure allows further corrosion attack on the underlying solder.

Abstract: Corrosion of metals in soil be able to change from comparatively fast material loss to insignificant effects, depending on soil environment. Corrosion is a process of deterioration of metal surfaces degraded into another compound. Soil is one of the medium known to have constituted to corrosion of metals. The soil creates an environment for the corrosion to react. The buried pipelines are exposed to the soil that may experience corrosion attack. The study of the soil as corrosion environment is important to mitigate the problem due to the environment and economy. There are factors that contribute to the corrosion process. This study concentrates on corrosion properties that expose to soil environment particularly underground pipelines. The mild steel coupons taken from actual pipelines, stimulating and analyzing the physic-chemical characteristics of the soil environment. The soil is sandy clay in natural. A total summed index of 2 numerical scale, thus, indicates that the soil tested was mildly to non-corrosive. The corrosion rate increase with increasing of moisture content and pH value. The observations on the coupon surface also did in order to study the morphology.