About Mechanism of Protection of Steel by PU-Stelpant Polyurethane Coatings

Issue 3(77) 2015
Pages 46-62

Е.S. Ivanov1, А.L. Кlyuev2, А.V. Аmezhnov3, А.S. Guzenkova4

1ОАО “All-Russian scientific Institute of corrosion” (ОАО “VNIIK”), Moscow
2Frumkin Institute of Physical Chemistry and Electrochemistry of RAS, Moscow
3Bardin FGUP «TsNIIChermet», Moscow
4National research university «Vyschaya shkola economiki NIU VShE», Moscow

Keywords: polyurethane, coating, steel, protected of corrosion, impedance spectroscopy (EIS), electron microscopy (SEM), fractal dimension, mechanism of protected action

Corrosion processes on carbon steel protected with Stelpaint polyurethane coatings have been studied by the methods of impedance spectroscopy (EIS) and electronic microscopy(SEM). Impedance specters have been received, equivalent schemes have been selected, modeled by the elements of impedance CPE Rs, Rp, Rct, the parameters values have been distinguished, analyzed and correlated with the physical processes on the metal beneath the film. SEM revealed fractality of polyurethane matrix, the mechanism of coating formation, its structural peculiarities.
SEM has defined the main composition of polymer matrix and fillers which influence upon the efficiency of anticorrosion protection. The concepts of fractal dimension of steel surface Dfm under the coating and fractal dimension. Dfn in the pores of polymer coating have been introduced. The correlation between Dfm and Dfn and the parameters Rp and Rct has been revealed. Zinc coating Stelpant-PU-Zinc demonstrated cathodic protection and form the physical barrier hampering the penetration of medium’s aggressive components. Stelpant-Pu-Mica HS and Mica UV contain mineral fillers provide the protection by forming a thick polymer matrix; flat particles of a filler create a «tile» effect forbidding the penetration of electrolyte. The layer coating Stelpant-Pu-Zinc + Mica HS + Mica UV proved to be more effective.