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Indian Journal of Chemical Technology (IJCT) >
IJCT Vol.12 [2005] >
IJCT Vol.12(3) [May 2005] >
| Title: | Microstructural and corrosion studies of 9Cr-1Mo steel in acidic methanol solutions |
| Authors: | Singh, V B
Gupta, Archana |
| Keywords: | Corrosion
9Cr-1Mo steel
potentiostatic technique
potentiodynamic technique |
| Issue Date: | May-2005 |
| Publisher: | CSIR |
| IPC Code: | C22C38/00 |
| Abstract: | The corrosion behaviour of 9Cr-1Mo ferritic
steel has been studied in methanol containing different concentrations of
sulphuric, hydrochloric acids and their mixtures using potentiostatic and
potentiodynamic techniques at 30 °C. The influence of various heat treatments:
furnace cooled (FC), air cooled (AC) and water quenched (WQ) on the
electrochemical polarization behaviour has also been studied for a few selected
compositions of these acids and their mixtures in methanolic solutions. The cathodic
reaction is observed to be hydrogen evolution. The alloy showed active, passive
and transpassive behaviour in different concentrations of sulphuric acid in
methanol. The anodic polarization curves of the alloy revealed a characteristic
‘cathodic loop’ in methanol at higher concentrations of sulphuric acid (0.1 and
1.0 M). Stable passivity was also observed which became ustable at higher
potential due to pitting. Well defined anodic Tafel region followed by a
limiting current density region, in different concentrations of methanolic
solution of hydrochloric acid, was observed. However, in the mixture of
different concentrations of sulphuric acid and hydrochloric acids in methanol
and at higher concentration of sulphuric acid (1.0 M) the alloy showed active,
passive and transpassive behaviour. Such behaviour was not observed below 1.0 M
concentration of either acid in methanol, rather a limiting nature was
observed. It seems that in the acidic mixture, the SO2-4
ions act as inhibitor and decreases the adsorption of Cl- ions and at sufficiently high concentration it effectively hinders
the adsorption of the Cl-
ions on the surface. The anodic polarization curves for FC specimen shifted
towards higher current density region and the curves for AC and WQ specimens
shifted towards lower current density region in comparison to as-received one
in methanolic solution of sulphuric acid. However, the anodic polarization
curves for FC, AC and WQ specimen shifted towards higher current density region
as compared to as-received specimen in methanolic solution of hydrochloric acid
and in the mixture of hydrochloric and sulphuric acids in methanol. Examination
of the sample surface was done using scanning electron microscopy (SEM). |
| Page(s): | 347-355 |
| ISSN: | 0975-0991 (Online); 0971-457X (Print) |
| Source: | IJCT Vol.12(3) [May 2005]
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