Is Ferric Oxide Protective or Not?

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SUMMARY

The discussion centers on the contradictory nature of Ferric Oxide (Fe2O3) as both a protective and non-protective agent in different environments. In the presence of strong oxidizing agents like concentrated nitric acid (HNO3) and potassium dichromate (K2Cr2O7), Fe2O3 forms a protective layer that prevents further corrosion. Conversely, when exposed to oxygen (O2), water (H2O), and hydrogen ions (H+), Fe2O3 contributes to rusting, indicating that its protective properties are highly dependent on environmental conditions.

PREREQUISITES
  • Understanding of corrosion processes and electrochemistry.
  • Familiarity with chemical reactions involving oxidizing agents.
  • Knowledge of the properties and formation of oxides, specifically Fe2O3.
  • Basic principles of passivation in metals.
NEXT STEPS
  • Research the mechanisms of metal passivation in the presence of oxidizing agents.
  • Study the electrochemical processes involved in rust formation and prevention.
  • Explore the differences in corrosion resistance of various iron alloys in different environments.
  • Investigate the role of environmental factors in the stability of protective oxide layers.
USEFUL FOR

Chemists, materials scientists, and engineers involved in corrosion prevention and metal treatment will benefit from this discussion, particularly those working with iron and its alloys in various chemical environments.

mooncrater
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Homework Statement


There are two lines in my textbook :
" Iron is passivated by strong oxidising agents like conc.##HNO_3,K_2Cr_2O_7## due to the formation of a protective coat of ##Fe_2O_3##."
And the other line says:
"Rusting occurs in the presence of ##O_2,H_2O## and ##H^+## resulting in the formation of ##Fe_2O_3## which is not protective and the corrosion continues"
Whats this? One line says that ##Fe_2O_3## is protective and other says it is not !

Homework Equations

The Attempt at a Solution


Can it be the reason that protective property of ##Fe_2O_3## is different for different conditions?
 
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mooncrater said:
Can it be the reason that protective property of ##Fe_2O_3## is different for different conditions?

Apparently. Concentrated nitric acid is safely transported in steel tanks, as the iron from these tanks gets passivated and doesn't dissolve in the acid. Same steel will rust if put in sea water.
 
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