Papers by Keyword: Corrosion Protection

Abstract: Fe-Nd-B Rare earth magnets are widely used in high performance applications but suffer from poor corrosion resistance due to their multiphase microstructure and the preferential dissolution of rare earth rich intergranular phases. In this study, the corrosion behaviour of Fe-Nd-B magnets was investigated and the effectiveness of electroless nickel coatings as a protective solution was evaluated. Microstructural and compositional analyses were combined with potentiodynamic polarisation tests, comparing bare and coated magnets with low alloy steel. Coating adhesion was assessed by pull off testing according to ASTM D4541. The results show that Fe-Nd-B magnets are significantly more susceptible to corrosion than steel, while nickel exhibits a passive behaviour in the investigated environment. Electroless nickel coatings provide effective protection and display adhesion comparable to that measured on steel substrates, demonstrating their suitability for corrosion protection of Fe-Nd-B magnets.

Abstract: Polymer coatings are thin layers of corrosion protection that can be applied to welded steel. Developing a polyester-based coating with metal fillers could assist homogeneous dispersion on weld surfaces. This study develops and characterizes the unsaturated polyester-Cu-Zn-Al₂O₃ coating and its corrosion performance on the welded steel. Cu-Zn-Al₂O₃ reinforcement was first milled at 40 h at 300 rpm, mixed with polyester to produce a film, and coated on welded steel. The results showed that milled consists of nanostructure and various particle distributions. The composition of the film consists of two distinct materials: amorphous polyester and crystalline Cu, Zn, and Al₂O₃. The ratio of these materials within the film influences its properties. The amount of filler in the polyester-Cu-Zn-Al₂O₃ composite film was maximum at 2.0 wt%. The corrosion rate monitored from 5 to 20 days shows a consistent trend, with 2.0 wt% showing the highest corrosion resistance.

Abstract: In the Philippines, bananas are one of the most exported agricultural products, with up to 6 million metric tons of annual harvest. Because of this, harvesting bananas generates waste like banana pseudo-stems. Banana pseudo-stems offer a good source of nanocellulose, and it was found that these have very similar chemical compositions to jute and sisal fibers, which are the most common sources of cellulose today. This only indicates that banana pseudo-stems could be utilized for different industrial and engineering applications. Epoxy-based nanocomposite coatings have attracted attention in industrial and engineering applications. Epoxy/banana pseudo-stem nanocellulose (Epoxy/BPNC) composites as anti-corrosive fillers were prepared by incorporating BPNC into the epoxy matrix to improve the anti-corrosion performance of epoxy coatings on mild steel surfaces. Their anti-corrosion properties were explored by the Tafel polarization technique under immersion in 3.5 wt.% NaCl solutions as corrosive medium. According to the results, it can be observed that epoxy/BPNC composite coatings significantly improve the anti-corrosion performance on mild steel surfaces with a 1.5 wt.% BPNC loading ratio as the optimized concentration. Furthermore, it can be seen that the optimized concentration of the BPNC loading ratio (1.5 wt.%) has a lower corrosion rate (CR = 2.7109 x 10^-6 mm/year) compared to that of the bare mild steel (CR = 6.11190 x 10^-2 mm/year). Additionally, the SEM results showed that the presence of BPNC in the epoxy matrix has a significant protective effect compared to pure epoxy alone.

Abstract: This paper presents the results of factorial experiment applied to optimize Matrix‑Assisted Pulsed Laser Evaporation (MAPLE) and Pulsed Laser Deposition (PLD) coating technologies used to improve the corrosion resistance of steels. MnTa₂O₆ pseudo-binary oxides and 5,10-(4-carboxy-phenyl)-15,20-(4-phenoxy-phenyl)-porphyrin was used for these experiments to obtained thin film coating system of hybrid nanostructures. Based on factorial experiments, correlations between the main technological parameters of the coating process (MAPLE laser energy E_MAPLE [mJ], PLD laser energy E_PLD [mJ]) and porphyrin concentration and the main related property of the coating system (corrosion protection factor) were determined. The base material used as substrate in the experiments was S235JR+C. Electrochemical measurements showed that by applying the appropriate parameters of the coating technologies, homogeneous layered sandwich thin films were obtained and corrosion rate was reduced by more than 7 times.

Abstract: It was defined that structural elements of a building made from electrically conductive concrete may reduce their performance characteristics due to the corrosion environment. The main reasons for that process are supplement corrosion factors such as a wide range of temperature, humidity as well as chemical agents in the environment. In this article results of different properties (mechanical, electrical) of electrically conductive concrete are discussed including their alterations due to sulphate attack. Also, microstructure as well as physical and chemical properties of modified concrete have been considered after being exposed to sulphate attack (Na₂SO₄) for 112 days. That component has been used for modeling the sulphate attack environment. Compressive strength, rate of the corrosion process, the volume of absorbed SO₄^2– ions from a water-based solution of Na₂SO₄ was defined in order to analyze the effect of sulphate attack. Scanning electron microscopic investigation, energy dispersive spectroscopy, differential thermal analyses were applied for observing morphology and properties changes of modified samples. To assess the influence of sulphate attack on mineral composite materials the approach was suggested and this method might be useful to foresee the durability of concrete while exposing it to the high corrosion environment. In addition to that, a possible method of protection for electrically conductive concrete from sulphate attack was also considered in the article.

Abstract: The technique of zero charge corrosion potential (ZCCP) acts as a new alternative of cathodic protection technique. A study of wave signal input in ZCCP technique was carried out on pure Mg steel in the 3.5% NaCl solution. This experiment was conducted within 48 hours. The wave signals input that had been used in this experiment are square, triangle, and sine wave. These waveforms have an impact on the corrosion protection of the ZCCP system. The effectiveness of waveform in ZCCP technique on corrosion protection was determined by morphology observation using stereomicroscope. It is found that, the lowest consumption of current density took placed at the square wave signal which is-0.99μA/cm². Meanwhile, for triangle and sine wave, the current density recorded were-1.694μA/cm² and-1.756μA/cm², respectively. From the morphology observations, it is clearly seen that the square wave signal provides better corrosion protection as compared to the triangle and sine wave signal. There is no formation of localised corrosion detected on the Mg surface using square wave signal. This is because the % ‘ON’ and % ‘OFF’ in ZCCP system allows to set it to the desired value of potential.

Abstract: Thermal energy storage (TES) systems have paramount importance in the design of Concentrating Solar Power (CSP) plants. TES systems allow storing the energy collected from solar radiation as heat energy in a thermal fluid and, in that way, extending the energy duration period of the plant and making the produced electricity dispatchable, depending on the actual demand and not only on the availability of the sun. The thermal fluids, synthetic oils, or molten salts, usually operate at temperatures from 500°C up to 800°C. The harsh operative conditions bring out issues related to the compatibility with the construction materials of CSP components, i.e., carbon and stainless steel. Coating of low-alloy structural steel with high-resistant materials has been addressed as a promising solution for mitigating the corrosion in TES system components. Compact plasma spray process was used to deposit Inconel 625 alloy onto T22 carbon steel coupons. Nitrate salts mixture, 60%NaNO₃-40KNO₃, commonly employed in CSP systems as operative and thermal storage fluid was used as corrosion medium. The tests were conducted by immersing coated and uncoated samples in molten salts at 500°C for 1, 3 7, and 14 days to assess the corrosion behavior of the In625 coatings. After 24 hours of exposition to molten nitrate salts, the T22 surface showed a pronounced oxidized layer having a thickness of approximately 20 µm. This layer is mainly composed of oxygen, iron, and chromium, which are the main constituents of carbon steel, with a few traces of sodium and potassium derived from the reaction of salts with the steel. Inconel 625, on the other hand, showed the formation of very thin scales of corrosion products localized only on the surface of the sample. Longer exposition is expected to produce a more pronounced degradation of uncoated steel, but barely affect the Inconel 625 coating

Abstract: A density functional theory (DFT) is used to investigate the energetics of an epoxy resin adhere on a tin oxide and a hydroxylated-alumina surface within a supercell approach. Self—consistent geometry optimization is performed for models of adhesion interface, which is comprised of a fragment of epoxy resin and hydroxylated-Al₂O₃ (001), and SnO2(001) and (110) surface. The epoxy resin studied was simplified fragment based on diglycidyl ether of bisphenol A (DGEBA). It is found that the distance between the resin and the surface where the adhesion force is maximized is substantially the same for all models. Analysis of the energy-distance plot reveals that the fragment of DGEBA molecule adhere most strongly to the SnO₂(001) surface, suggesting that the adhesion force is induced by van der Waals (vdW) interaction.

Abstract: Aluminium alloys are among the metals that can be easily passivated, demonstrating notable anticorrosion properties. Under aggressive environments, like in seawater, corrosion may appear though due to presence of chloride ions (pH>8.5) leading to pitting failures. The objectives of the presented research were to examine the possibility of functionalizing the surface of an aluminium alloy through a polydopamine (PDA) layer with homogeneously dispersed silver nanoparticles (AgNPs) and examine the corrosion behaviour of the nanostructured coating. The development of a PDA coating provides a promising approach for immobilization of silver nanoparticles onto AA6061 substrate. Exposure to salt spray for 60 h and assessment of the corrosion status through various methods were applied. Depending on the process parameters for the fabrication of the PDA-AgNPs layer, an enhanced corrosion protection was achieved compared to the undoped with AgNPs film and the uncoated Aluminium alloy.

Abstract: Creation of new efficient composite materials and the technologies of their manufacturing are inseparably coupled with corrosion protection of cement stone, which allows preserving construction products from fracture and ensuring their long service life. The development of new compositions of composite materials based on the industrial wastes from regional enterprises and aimed at the corrosion protection of construction products and structures is an urgent task for construction and technology professionals. A filled two-component polymer system (FTPS) for complex protection of construction materials and structures against moister and aggressive environments, which is based on secondary polymer and mineral raw materials, exhibits impregnating properties and can be used as a polymer additive to cement binding matter. The new mineral-polymer binder significantly changes the properties of the resulting material providing it with corrosion-resistance. The introduction of the FTPS polymer component in addition to the main mineral binder (cement) into the composition of concrete mix will allow changing the properties of concrete compositions through the modelling of their internal structure.