Question : The zinc is actually chipped of. So why doesn't the iron rust?
Answer : It will, just give it some time.
Even after chipping, the zinc metal will protect the very surface of the iron with a very thin layer of zinc atoms which must be removed first. Rain water will usually be able to accomplish this.
There is also an electrochemical effect of the other zinc atoms in contact with the iron which will help prevent immediate oxidation of the iron.
A drop or two of dilute acid on the exposed iron surface will show rust usually within 24 hours or less. Natural exposure may take a little longer.
Question : (Name all the metals that can rust, please.)
Answer : Steel is actually made from iron, so yes, it can rust.
Some other metals (like aluminum) will oxidize.
Question : For example, what would be the chemical reaction (as simple as can be) of an iron nail rusting?
Answer : The rusting of iron is an electrochemical process that begins with the transfer of electrons from iron to oxygen.The rate of corrosion is affected by water and accelerated by electrolytes, as illustrated by the effects of road salt (calcium chloride) on the corrosion of automobiles. The key reaction is the reduction of oxygen:
O2 + 4 e- + 2 H2O 4 OH-
Because it forms hydroxide ions, this process is strongly affected by the presence of acid. Indeed, the corrosion of most metals by oxygen is accelerated at low pH. Providing the electrons for the above reaction is the oxidation of iron that may be described as follows:
Fe Fe2+ + 2 e
The following redox reaction also occurs in the presence of water and is crucial to the formation of rust:
4 Fe2+ + O2 4 Fe3+ + 2 O2
Additionally, the following multistep acid-base reactions affect the course of rust formation:
Fe2+ + 2 H2O -> Fe(OH)2 + 2 H+
Fe3+ + 3 H2O -> Fe(OH)3 + 3 H+
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