3951

3729

كارشناسي ارشد

خوردگي و حفاظت از مواد

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد

1386

ده، 111،[II]ص: مصور، جدول، نمودار

ص.ع. به: فارسي و انگليسي

محمد علي گلعذار، كيوان رئيسي

21/3/87

احمد ساعتچي، ابوالقاسم دولتي

مهندسي مواد

ID3729

به فارسي و انگليسي: قابل رويت در نسخه ديجيتال

AbstractNanocrystalline coatings of Ni Co were deposited on a carbon steel substrate viaelectrodeposition by direct current in a Watts type bath with and without Saccharinaddition The current densities used were 5 12 39 55 and 104 mAcm 2 The resultsobtained showed that when Saccharin is added to plating bath reduces grain size abouthalf increases hardness about twice changes texture from 311 and 200 to 111 and morphology from pyramidal to smooth In the absence of saccharin current densityand adsorption of hydrogen complexes and or intermediate components were distinguishedas two effective parameters causing nanocrystalline electrodeposits In the presence ofsaccharin Adsorption of saccharin molecules and or decomposed sulfide species occurredin saccharin contained bath resulted in slow surface diffusion of adions and thus inhibitsfrom grain growth and encourages finer grain structure formation Tafel polarization testresults showed that coatings obtained from with Saccharin bath in spite of those obtainedfrom without Saccharin bath could not form a passive film in 3 5 wt NaCl EIS testresults showed that decreasing the grain size from micro to nanocrstalline doesn t decreasecorrosion performance of Ni Co coating in 10 et NaOH The tribo corrosion tests showedthat the coating obtained at the higher current density 55 mA cm 2 had the same opencircuit potential OCP before during and after the sliding wear test This was attributed toits strong repassivation ability probably provided by its morphology This behavior was notobserved for the coatings deposited at a lower current density 39 mA cm 2 or at thepresence of sodium luryl sulfate These coatings showed a lower OCP during and after thesliding wear probably due to the high ratio of active to passive area on their worn region Adding saccharin into bath resulted in more corrosion rate and change of sliding wearmechanism from abrasive to adhesion It showed an OCP increase exceeded than theinitial potential during the sliding wear and a sudden decrease after removing the slidingload The reason was postulated to be a soluble semi passive film formation encouraged bythe induced structural inflects on the worn area and supported by the presence of thesliding load

محمد علي گلعذار، كيوان رئيسي

احمد ساعتچي، ابوالقاسم دولتي