ارزيابي خواص و بررسي الكتروشيميايي جدايش كاتدي پوشش پلي يورتان

چكيده انگليسي :

Evaluating of Properties and Electrochemical Investigation of Cathodic Disbondment of Polyurethane Coats Sina Saeedy sina na s@yahoo com sep Department of Materials Engineering Isfahan University of Technology Isfahan IranDegree M Sc Language FarsiAhmad Saatchi asaatchi @gmail comAbstractBy diffusion of water and other factors which cause cathodic disbondment in the polymeric coat and reachingmetal polymer interface hydroxyl is produced and makes the interface alkaline The alkalinized interface causesdisbondment of polymeric coat from metallic substrate The scope of this project is to evaluate the cathodicdisbondment of polyurethane coat which is used to protect oil and gas pipe lines The quantity of cathodicdisbondment of a polymeric coat depends on two parameters These two parameters are adhesiveness of polymericcoat to metal substrate and resistance of polymeric coat to diffusion of water and other factors which cause cathodicdisbondment For having a valid study on cathodic disbondment phenomenon these specifications should beevaluated In this project according to Iranian gas standards these parameters are studied The resistance of thepolymeric coating to diffusion of water and other factors is studied by two quantitative tests including waterabsorption test and chemical resisitance test performed in acidic solution alkaline solution pure water and salinesolution So the amount of absorbed water and reagents in saturated condition is measured and compared to thestandards Also adhesiveness is studied by two qualitative test including resistance to removal test and hot watersoak test and one quantitative test including pull off strength of coatings using portable adhesion testers It is shownthat both specifications of the polyurethane is in the standard range After investigating these two parameters cathodic disbondment is measured For evaluating cathodic disbondment a simple electrochemical cell is set up andspecimen is connected to negative terminal of a rectifier and the positive terminal is connected to a platinumelectrode so the specimen is under cathodic protection for a assessed period of time The measured quantity ofcathodic disbondment is more than what assessed in the standard Noting that the resistance of the polyurethane todiffusion of water and other reagents and also adhesiveness of polymeric coat to the metal substrate are in thestandards range it can be concluded that surface unevenness of polymeric coat created by using a brush forpainting causes residual stress in polymeric coat The created residual stress aids the disbonding of polymeric coatfrom metal substrate and increases the amount of cathodic disbondment One of affective parameters on cathodicdisbondment is the thickness of polymeric coat For evaluating the parameter of thickness cathodic disbondmentand coat resistance of three different polyurethane thickness are measured Three double electrochemical cell is setup for this test to measure the polymeric coat resistance and the quantity of cathodic disbondment coincidely Specimens as the chathodic disbondment test are under cathodic protection for the same period of time It is shownthat increasing the coat thickness will increases the polarization resistance and pores resistance of polymeric coatand the quantity of cathodic disbondment decreases Also by electrochemical test is shown that pores of a polymericcoat have an important role in efficiency of coat Increasing the amount of pores of a polymeric coat will increasethe quantity of cathodic disbondment So it is concluded that increasing the thickness of coat will increase theresistance of polymeric coat and reduces the cathodic disbondment of a non porous polymeric coat key wordsCathodic Disbondment Cathodic Protection Polyurethane Pipe line

سعيدي، سينا

ارزيابي خواص و بررسي الكتروشيميايي جدايش كاتدي پوشش پلي يورتان

حفاظت كاتدي , خط لوله