Development of functional waterborne corrosion protection coating by application of novel types of dispersants and wax emulsions

Cilj ovog rada bio je razvoj vodene disperzije s nanočesticama TiO2, koja uz dodatak različitih aditiva, može služiti kao funkcionalni premaz protiv korozije nehrđajućeg čelika. Na putu razvoja takvog funkcionalnog premaza stoje razni izazovi poput: izbjegavanja aglomeracije nanočestica, postizanja jednolikog sloja na površini metala i potiskivanja osjetljivosti površine ispitivanog nehrđajućeg čelika na lokaliziranu koroziju. Disperzijama su dodavani komercijalni disperzant ili NaNO3 čija je uloga bila sprječavanje aglomeracije čestica i komercijalni vosak koji mijenja viskoznost disperzije, a time i njezina svojstva pri nanošenju. Dobivene otopine okarakterizirane su apsorpcijskom spektrometrijom pri λ = 430 nm i mjerenjem pH, dok se funkcionalnost premaza ispitivala elektrokemijskim mjerenjima. Nakon ispitivanja, površina metala se pregledavala pod svjetlosnim i elektronskim mikroskopom. Ispitivano je nanošenje uranjanjem sa sušenjem premazane plohe u okomitom i vodoravnom položaju, te nanošenje kapanjem i sušenjem u vodoravnom položaju. Najboljom su se pokazale vodene otopine nitratne kiseline pH 2 s 1 gl^-1 TiO2 nanočestica bez i sa dodatkom komercijalnog disperzanta nanesene kapanjem koje su, osim stabilnosti, pokazale umanjenu struju u pasivnom području, povišen potencijal jamičaste korozije, prošireno pasivno područje te izraženi efekt fotogenerirane katodne zaštite pod UV osvjetljenjem.Purpose of this paper was development of water dispersion with TiO2 nanoparticles, which, when supplied with different additives, can serve as a functional coating against stainless steel corrosion. There are multiple challenges and obstacles in developing that kind of functional coating like: avoiding nanoparticle agglomeration, achieving uniform layer on metal surface and suppressing surface sensitivity of subjected stainless steel on localized corrosion. Commercial dispersant was added to dispersions, or NaNO3, whose purpose was to prevent particle agglomeration and commercial wax which changes viscosity of dispersion, with that its properties during application. Prepared solutions are characterized with absorption spectrometry on λ = 430 nm and measuring pH, while coating functionality was tested using electrochemical measurements. After testing, metal surface was observed through light and electron microscope. Application by dip-coating with drying of coated surface in vertical and horizontal position was tested, so as dripping and drying in horizontal position. Water solutions of nitrate acid pH 2 with 1 gl^-1 TiO2 nanoparticles with and without commercial dispersant applied by dripping have shown best results. Other than stability, reduced current in passive area, enhanced potential of pitting corrosion, enlarged passive area and conspicuous effect of photogenerated cathodic protection under UV lighting was observed