Is bronze tarnish electrochemical corrosion or chemical corrosion?

[Yeahaight]

Homework Statement

Is bronze tarnish electrochemical corrosion or chemical corrosion?
Bronze is outside, reacting with air.

Relevant Equations

no

I can't figure it out.

 

[Borek]

What definitions of chemical and electrochemical corrosion are you expected to use?

My bet is that it is one of these cases where an attempt at classification is futile and a waste of time.

 

[Andrew Mason]

Homework Statement:: Is bronze tarnish electrochemical corrosion or chemical corrosion?
Bronze is outside, reacting with air.
Relevant Equations:: no

I can't figure it out.

Since all chemical reactions are rearrangements of atoms due to electric forces, whether a reaction is considered chemical or electrochemical depends on how it occurs, not what it results in.

My understanding is that if the reaction occurs with the atoms of both elements physically together at the same location then it would be classified as a chemical reaction. If there is a distance between the atoms of both elements so that the electronic reconfiguration occurs at a physically separate distances with the bonds between the two atoms resulting from the movement of ions and electrons from physically separate locations, then it is classified as electrochemical (since movement of charges - ions and electrons - constitutes an electric current).

Since tarnish occurs because the oxygen atoms in the air come into contact with the copper atoms in the bronze surface, it would be classified as a chemical reaction.

AM

 

[Borek]

Trick is, metal corrosion often happens with red and ox counterparts being separated and charge being transferred between them through metal and electrolytes - that why salty water speeds up this type of corrosion (by making it easier to transfer the charge). Then, despite everything being in place, the process is definitely electrochemical. As there can be any combination of reactions, classifying arbitrarily "this is chemical" or "this is electrochemical" is in some cases either difficult, or futile.