Browsing by Subject "obszar przedpasywny"

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Access status: Open Access ,
Wpływ zawartości chromu w niskostopowych stalach konstrukcyjnych na ich właściwości elektrochemiczne i odporność korozyjną w roztworach wodnych
(Data obrony: 2012) Łukaszczyk, Alicja
Wydział Odlewnictwa
The object of this study was to investigate the effect of chromium content in low alloy constructional steels on their electrochemical properties and corrosion resistance in aqueous solutions. The tests were performed on pure iron, binary $Fe- Cr$ alloys with chromium contents of $1, 3 and 5\%$, and casting alloys. There were used polarization techniques. After the electrochemical tests there were examined the surfaces of $Fe-Cr$ alloys. In addition to laboratory tests, there were performed field tests of $Fe-Cr$ alloys in corrosion monitoring stations in polish heating plants. Constructional steels containing small amounts of chromium are more resistant against corrosion in the system of thermal water, than carbon steels without chromium. The presence of chromium increases the anodic activity of ferrite, which results in rapid saturation of the surface with the anodic reaction product. With the increase in chromium content decreases the thickness of surface layer. The protective properties of this layer grows with increasing chromium content in the alloy. Microstructure of low-alloy structural steels has a significant effect on their corrosion properties in thermal water. Heat treatment of steel, leading to the formation of pearlitic or bainitic structure, causes the improvement of the barrier properties of corrosion products film. Fragmentation of microstructure increases the anodic current density on the surface of the matrix and thereby increases the rate of nucleation of the anode product. This leads to the creation of films with better barrier properties.