Corrosion Mechanism for Stainless Steel

​
potential
0.1
domain
all
activity
prepassivity
passivity
transpassivity
Fe +
H
2
O → FeOH
+
)
ads
+
+
H
+ 2
-
e
FeOH
+
)
ads
+
+
H
→
2+
Fe
+
H
2
O
​
Corrosion degrades materials, which is a source of significant expense. This Demonstration explains how steel corrodes. A steel plate (whose main component is iron) is corroded in an acid solution. This plate plays the role of a working electrode in an electrochemical cell, for which the current and potential can be measured.

Details

When the metal is dissolved in a corrosive environment, the anodic reaction takes place at the interface.
In the activity domain, the anodic current increases and the overall reaction is
Fe→FeOH
+
)
ads
→
2+
Fe
.
In the prepassivity domain, the formation of the oxide film
Fe(OH)
2
protects the metal from the corrosive environment. The anodic current decreases according to the reaction
+
Fe(OH)
ads
+
H
2
O→
Fe(OH)
2
+
+
H
+2
-
e
.
In the passivity domain, the protective layer totally separates the metal from the environment. The anodic current is stable and at a minimum.
In the transpassivity domain, the layer ruptures. The metal continues to corrode and the anodic current again increases via
Fe→
2+
Fe
+2
-
e
.

Permanent Citation

Quang-Dao Trinh
​
​"Corrosion Mechanism for Stainless Steel"​
​http://demonstrations.wolfram.com/CorrosionMechanismForStainlessSteel/​
​Wolfram Demonstrations Project​
​Published: December 1, 2011