Why does steel rust fast while iron is more passive

Why does steel rust fast while iron is more passive  

Steel is an impure form of iron, the most common contaminants being carbon (from the coke that fuels the smelting process) and sulphur from the iron oxide ore. 

Pure iron is relatively reactive, so, given time and suitable conditions of water and oxygen, it forms a layer of red hydrated iron oxide ( rust )  

Many iron ores also contain iron sulphide, which is commonly called fool s gold. 

By contrast, steel is considerably more reactive, and rusts faster extent. 

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