Development of coating for temporary corrosion protection of steel under highly corrosive environmental conditions

U ovom radu analizirane su tri vrste premaza u razvoju elektrokemijskom impedancijskom spektroskopijom. Analizirane vrste premaza bile su akrilni, uretanski i premaz na bazi vode. Svi premazi su sadržavali inhibitore. Uzorci premaza su bili naneseni u tankom sloju na tanke čelične ploče. Prije karakterizacije metodom EIS, neki od uzoraka bili su uronjeni u ćeliji, dok su drugi bili izloženi u slanoj komori. Svrha eksperimenata bila je donijeti zaključke o promjeni kvalitete premaza ovisno o vremenu izloženosti u visoko korozivnim okolinama. Po jedan uzorak od svake tri vrste premaza podvrgnut je analizi uz pomoć velike ćelije kako bi se vidjele posljedice uronjenosti u 3 %-tnu otopinu NaCl-a i promjene u impedancijskom odzivu i izgledu premaza u ovisnosti o vremenu izloženosti. Drugi uzorak od svakog premaza bio je izložen u slanoj komori u magli 5 %-tne otopine NaCl-a te se također promatrala vremenska ovisnost stanja premaza uz provjere približno svakih sedam dana. Analizom dobivenih EIS spektara utvrđeno je da s vremenom dolazi do pada zaštitnih svojstava premaza. To se može zaključiti na temelju pada vrijednosti dobivenih impedancija te porasta faznog kuta. Nema značajnih razlika u kvaliteti tri analizirane vrste premaza, ali moglo bi se reći da se kao najbolji pokazao premaz na bazi vode, zatim uretanski te akrilni premaz. Postoji mogućnost kompenziranja propadanja premaza djelovanjem inhibitora. Djelotvornost inhibitora je za većinu mjerenja bila iznad 98 %. Primjećuje se da je djelotvornost inhibitora najviša kod akrilnog premaza.In this paper three different types of coatings in development were analysed using electrochemical impedance spectroscopy. Analysed types of coatings were acrylic, urethane and water based coating. All of them contained inhibitors. Samples of coatings were applied in thin layer on thin steel plates. Before characterization using EIS method, some of the samples were immersed in cell, while the others were exposed in the salt chamber. The objective of experiments was to come up with conclusions regarding the performance of coatings depending on the time of exposure in highly corrosive environments. One sample of each three types of coatings was subjected to analysis using a cell aiming to see the consequences of immersion in 3 % NaCl solution, changes in impedance response and the look of coating depending of the exposure time. Second sample of each type was exposed in the salt chamber in fog of 5 % NaCl solution, time dependency of coating state was also analysed every seven days approximately. Analysis of obtained EIS spectres showed that protective properties of coatings decrease with time. That was concluded according to decrease of the values of impedances and increase of phase angles. There are no significant differences in quality of three analysed coatings, but we could say that water based coating showed as the best, then urethane and at the end acrylic coating. There is a possibility of compensation the coating degradation with inhibitor influence. Effectiveness of inhibitor was above the value of 98 % for most of the measurements. It was noted that inhibitor effectiveness was the biggest on acrylic coating