Yeni Nesil Sünek Dökme Demir Malzemenin Basamaklı Polimerizasyon Yöntemi ile Hazırlanan Epoksi Reçinelerle Korozyona Karşı Korunması

Abstract

In recent years, the importance of cast iron has increased considerably in the metallurgy and materials science. Unlike the primary generation cast iron, a new class of spheroidal cast iron emerged at the end of the 20th century, called the second generation. These materials, called solid solution strengthened ferritic ductile iron (SSF), which is reinforced by solid solution, have become a material class which is very advantageous for metallurgical industry as it is cheaper than steel and has high elongation values as well as being ductile, yet not as complex as steel's chemical structure.

In this thesis, it was aimed to find out the suitable chemical composition for the production of EN-GJS-600-10 material, which is one of the new generation of spheroidal cast iron materials that not yet been widely produced, for the purpose of providing mechanical properties given in corresponding standards, and then to modify the surface of this material with a suitable polymer to render it resistant to corrosion and abrasion in use in industries such as the defense industry. The new generation ductile spheroidal cast iron material was obtained by mixing 16 different elements such as iron (Fe), silicon (Si) manganese (Mn), carbon (C), and magnesium (Mg) with appropriate ratios. These elements were assembled at various amounts and in the end; optimum ratios were determined to meet the criteria defined in the standards for both chemical composition and mechanical properties. Production of the prepared cast iron material is not widespread in the world. Industrial production is not yet optimized in our country. In the scope of the thesis, significant results were obtained in terms of surface modification against corrosion and preparation of new generation metallic alloy having 16 elements in its chemical composition, being cheaper and lighter than steel, and yet having properties approaching to those of it. Surface modification is a frequently used method to obtain the surface properties desired in academic and industrial studies. In particular, modification of the metal surfaces against corrosion is essential for their use in many applications. In the scope of the thesis, epoxy resin formation was provided on metal surfaces by step-growth polymerization method and the resistance of these surfaces against corrosion was investigated.

Corrosion tests have shown remarkable resistance to corrosion on metal surfaces. Ethylene glycol, alcohol type of 5 monomers studied, failed to demonstrate the desired performance in surface modification. The weakest resistance amongst the 4 amine type monomers was found in the presence of ethylene diamin (EDA), a diamin. Resins synthesized using -tri, -tetra and -penta, in particular -tetra and -penta, amines presented better barrier properties against corrosive gas, liquid or dissolved species by preventing the diffusion of these species thorough the bulk of the polymer matrix. The main reason for this is that the chain length between the cross-links is shorter and/or the free volume voids between the cross-links are filled more densely, depending on the high branching, and thus higher barrier properties are obtained.

Significant results have been obtained demonstrating the importance of proper adjustment of the stoichiometric ratio between the monomers used in step-growth polymerization in order to obtain a corrosion resistant resin. Di-epoxy:amin monomer ratio of 2:1 showed higher resistance to corrosion among the formulations used for the synthesis of resin samples except for those prepared using EDA. 2:1 mole ratio may have caused a denser cross-linking in the resin structure and may have increased barrier properties by shortening the chain lengths between the cross-links.

At the end of the corrosion test, no blistering was detected in any of the surfaces by microscopic examination of metallic surfaces. This is an important finding in terms of the durability of the surface coating as blisterization increases the corrosion by causing the paint to swell on the surfaces. As a corrosion inhibitor, the effect of benzotriazol (BTA) was investigated and the results were indicated that BTA had a positive effect on corrosion prevention. BTA is thought to form a thin layer on the metal surface and/or clusters in the bulk of the resin which act as barrier-like structures.

The metallic materials developed within the scope of this thesis are thought to be important for our country, especially for defense industry, and to have economic value. It is thought that the part of the thesis related to the preparation of anti-corrosive polymeric coating is important especially in terms of presenting some basic criteria.