توليد، مشخصه يابي و ارزيابي رفتار خوردگي پوشش هاي آلومينيوم اعمالي به روش پاشش قوس الكتريكي براي كاربردهاي دريايي

چكيده انگليسي :

80Characterization and Corrosion Behavior of Arc Sprayed Al Coating for Offshore Applications Erfan Abedi Esfahani e abediesfahani@ma iut ac ir Department of Materials Engineering Isfahan University of Technology 84156 83111 Isfahan IranDegree M Sc Language FarsiDr Hamid Reza Salimi Jazi Assist Prof Supervisor E mail hrjazi@cc iut ac irDr Mohamad Ali Golozar Prof Supervisor E mail golozar@cc iut ac irAbstractPlain carbon steels are widely utilized in structures because of their suitable mechanical properties goodperformance and low cost However in some harsh environments such as salty atmosphere corrosion ofcarbon steels becomes a major concern and limits their applications An effective way to improve thecorrosion resistance of steel is to use a protective coating on the surface Organic coatings such as paints arewidely used to protect steel structures against corrosion In order to improve corrosion resistance of organiccoatings intermediate layers of metal coatings can be used Amongst various types of thermal sprayprocesses twin wire arc spray is widely used for deposition anticorrosion coatings This is due to itseconomical advantages and the high deposition rate A very wide variety of metallic coatings are used toimprove corrosion resistance of steels The most commonly used metals for protection of steel againstcorrosion are anodic to substrate which eliminate the need for completely pinhole free barrier In The currentstudy aluminum coating was deposited on carbon steel by twin wire arc spraying SEM micrographs showedthat a well adhered coating with low level of porosity and oxide content was successfully deposited Novisible microcracks were detected in the coating Coatings adhesion was measured by ASTM C633 standardand it showed that the adhesion strength of the coatings was slightly higher than those reported by otherresearchers To evaluate the corrosion behavior of the coatings electrochemical impedance spectroscopy EIS were employed during long time immersion in 3 5 NaCl solution The as coated samples were alsosubjected to a 1500 hour salt spray assay Polarization tests indicated that the corrosion current density of thealuminum coating is much more than that for bulk aluminum This behavior could be due to the penetrationof the electrolyte through porosities results in accelerating aluminum corrosion EIS measurements showedthat the corrosion performance of coatings is improved by increasing immersion time in 3 5 NaCl solutionas well as exposure to saline mist This could be due to plugging of pores by corrosion products which hinderfurther penetration of the electrolyte through the coating The corrosion products formed on the surface of thecoatings were evaluated by X ray diffraction and confirmed oxide formation Despite the fact that thecorrosion performance of the coating was improved during long time immersion in NaCl solution and salinemist oxide content of the coatings was increased results in decreasing the cohesion strength of coating Tostudy the effect of sealing process on the corrosion behavior of thermally sprayed coatings coating sampleswere coated by a conventionally zinc phosphate pigmented paint EIS measurements and salt spray assayshowed that the corrosion behavior of coated and painted samples was much better than aluminum coatings They were immune from interior corrosion attack during long time immersion The better performance ofsuch duplex coating systems has been attributed to the synergy between the cathodic protection provided bythe sacrificial coating of metallic coating and the combined barrier resistance of the metal and organiccoatings Keywords Wire arc spray Aluminum Carbon steel Zinc phosphate Electrochemical impedancespectroscopy Salt spray

عابدي اصفهاني، عرفان

توليد، مشخصه يابي و ارزيابي رفتار خوردگي پوشش هاي آلومينيوم اعمالي به روش پاشش قوس الكتريكي براي كاربردهاي دريايي

فولاد ساده كربني , رنگدانه فسفات روي , طيف سنجي , امپدانس الكتروشيميايي , پاشش نمك