Corrosion of Steel: Equilibrium & Rate Drop

[supasupa]

Say is a piece of steel is placed in still water and is corroding. Why will the corrosion rate drop away after time??

Is it because the system reaches some sort of equlibrium??

 

[supasupa]

thats ment to say : "Say if a piece of steel..." NOT " Say is a piece..."

 

[haynewp]

I believe the layer of corrosion protects it. Corrosion rates are higher in moving water because the corrosion covering is always being washed away.

 

[supasupa]

that makes sense... what you are saying is the oxide around the steel (rust) slows down the corossion rate

 

[Hootenanny]

that makes sense... what you are saying is the oxide around the steel (rust) slows down the corossion rate

That is correct. This is the theory behind anodising aluminium (although aluminum oxide also exhibits excellent thermal insulation properties)