جستجوی مقالات مرتبط با کلیدواژه "corrosion protection" در نشریات گروه "فنی و مهندسی"

Corrosion is a harmful phenomenon for metals have been utilized in various industries like aerospace. Uniform, galvanic, pitting, intergranular, and crevice corrosions are types of corrosion causing approximately 20% of the whole repairing costs of aircraft. The flying condition alters during the flight results in enormous problems for an aircraft. Several methods have been reported to diminish the corrosion rate in which the protective coatings have been exploited in this assessment. To this end, three-layer coating employed to apply on the steel and aluminum substrates. Middle layer and top coat were similar relating to high-build epoxy and polyurethane, respectively. However, zinc-rich epoxy was applied on the steel substrate and neat epoxy was employed for aluminum for the primer layer. The airless spray was used to fabricate different coating determining 6-24 h for curing of each layer. EIS results illustrated that this coating protective system showed just one-time frequency response after 1000 h immersion in 3.5% NaCl exhibiting the fact that water molecules could not penetrate through the coating and access the substrate after 1000 h. Additionally, the low-frequency response of EIS plots confirmed the excellent anti-corrosive performance of coating system applied on the aluminum. Moreover, the pull-off test clarified the reasonable adhesion strength of the coating system on both aluminum and steel substrates.

Nowadays due to water shortage, the use of treated wastewater as sustainable solution has been considered by industrial units; especially in industrial cooling units and boilers. However the use of treated wastewater also has its own problems such as corrosion of metal parts that they are often made of carbon steel. Therefore different methods such as coating have been considered by the industrial user of treated wastewater in order to reduce corrosion. So in this study, SiO2/TiO2 Ceramic Nano composite coatings was put on Carbon Steel plates by Sol-Gel method and by dipping process for 100 seconds and microstructure and properties of produced ceramic coatings were investigated. The results showed that ceramic Nano composite coatings improved corrosion properties of Carbon Steel. In order to improve the properties and performance of the coating, the molar ratio of components and factors affecting performance of coating were evaluated till optimum coating with Nano structure and highest level of corrosion protection is provided. To evaluate the performance of coatings for corrosion protection, polarization curves and to determine the surface morphology, scanning electron microscope was used. In order to study the bonds type and functional groups in the optimal sol, infrared spectrum was used. The optimum corrosion protection coatings were studied in 3.5% sodium chloride solution. The results showed that the ceramic optimal deposited coating provides effective protection for the surface of Carbon Steel against corrosion in 3.5% sodium chloride solution.

In this study, a commercial zirconic acid based pretreatment was performed on hot dip galvanized steel sheets via immersion process. The effect of pH on morphology, composition and electrochemical behavior of the conversion layer was investigated. Field emission scanning electron microscopy (FE-SEM) coupled with energy dispersive X-ray spectroscopy (EDS) were carried out to study the morphology and composition of the surface after treatment. Also, DC polarization and EIS were used to evaluate the corrosion behavior of the treated surface in 3.5 wt.% NaCl. Electrochemical results revealed that the best anti-corrosion performance with the lowest current density and highest Rp value, belongs to the conversion coating obtained in acid concentration of 3% and pH= 5 for galvanized steel samples. EDS results disclosed that conversion coating consisted of: Fe, Zn, O, Zr and C confirming a dense ZrO2 layer is formed on galvanized steel samples. Furthermore, FE-SEM images showed that a uniform and compact layer of conversion coating is obtained on galvanized steel surface in pH=5 which corroborates EDS and electrochemical consequences.

School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran The paper intends to introduce innovations in the field of silane based coatings. Although the coatings are generally thin, they are able to provide a desirable corrosion protection. Hence, they could be taken into account as proper alternative for toxic chromate conversion coatings. In addition to protective action, silane layer can facilitate an excellent adhesion for the covering coating through covalent bonds. In spite of barrier properties, the coatings would fail to reveal active protection in case of introducing cracks or failures. Main aim of the paper is to introduce some novel approaches to improve protective performance of silane based coatings.