Corrosion vs. oxidation:
Oxidation is the loss of an electron (this is always coupled with another substances gain of electrons since electroneutrality must be maintained). So Cu--> Cu2+ +2e- is an oxidation of elemental copper to copper ion.
Corrosion: Closely related (in natural systems) to oxidation, the reaction of a metal ion with (usually) water to form hydroxides and oxides.
Cu 2+ + 2H2O --> Cu(OH)2 + 2H+
Rust is a ubiquitous corrosion product.
Strictly speaking, galvanic corrosion is when metals with different redox potentials come in contact with one another in an electrically conductive medium (water). Here is a good explanation from my alma mater:
http://www.ocean.udel.edu/mas/masnotes/corrosion.html
Regarding the chemicals in water wetter:
Bacteria and fungi typically grow in slightly to moderately acidic conditions. Water wetter is basic and so the pH of the water is not as hospitable to microbes. Surfactants may or may not participate in the reduction of microorganisms; not my field. I would tend to think of them as a carbon source and therefore potentially another food source for microbes.