what is the chemical formula of corrosion with steel ? and what metals are steel made out of?

Question

I am doing an experiment on corrosion and would like the answer to my question.

 

thanks

Answer 1

Steel is basically iron with other trace metals incorporated to give various properties. The metals combined with iron in steel vary, and there are basically 4 types of steel

1. Carbon steels (generally contain .1-1.5% carbon in iron (most often 0.1-0.25%))

2. Alloy steels contain metals such as manganese, silicon, nickel, titanium, copper, chromium, and aluminum) in varying proportions in order to manipulate the steel's properties, such as hardenability, corrosion resistance, strength, formability, weldability or ductility

3. stainless steels (contain 10-20% Chromium to give corrosion resistance)

4. tool steels (contain tungsten, molybdenum, cobalt and vanadium in various amounts to increase heat resistance and durability.

 

Corrosion

To corrode steel you basically have a redox reaction and need both water and oxygen.

The anode reaction is Fe ---> Fe⁺² + 2 e^-

The cathode reaction is O₂ + 2 H₂O + 4 e^- ---> 4 OH^-

 

Together this gives you 2 Fe  + O₂ + 2 H₂O  ---> 2 Fe(OH)₂

 

 Oxygen then reacts with the Iron(II)hydroxide to form hydrated Iron (III) oxide

 

4 Fe(OH)₂+ O₂  → 2 H₂O + 2 Fe₂O₃.H₂O

 

All together this is:

4 Fe + 3 O₂ + 2 H₂O ---> 2 Fe₂O₃^.H2O