Re: What bactericides could be used in preventing the growth of rust on nails?

As I do with so many of the questions I answer on MadSci, I have to add the 
disclaimer that I have no direct experience in this area and I have not 
specifically read papers dealing with the particulars of this issue.  First 
one must recognize that rust will be formed on iron surfaces without the 
action of bacteria.  Killing off the bacteria will not prevent rust from 
forming.  This is a purely electrochemical process that can occur 
chemically.

Bacteria have been implicated in contributing to the process of corrosion.  
It is suggested that bacteria produce organic acids during normal metabolism 
and that these organic acids then complex metals ions near metal surfaces.  
The acids help to dissolve the metals.  Increased acid production occurs 
when bacteria or fungi are grown under anaerobic conditions (no oxygen) 
where they perform fermentation reactions.  The acids produced, lactate, 
oxalate, citrate, etc., can be corrosive to metals.  In addition, 
extracellular polysaccharides produced by microbes can also bind metal ions.  
Thus, as metal ions dissolve from a surface they are captured from solution 
by the extracellular polysaccharides, driving the reaction towards 
dissolution through mass action (removing the product, a dissolved metal 
ion).  

There is extensive research covering another aspect of microbially induced 
corrosion.  Here metal dissolution takes place at an anodic site on the 
surface, with transfer of electrons to a second cathodic site where they are 
removed from the metal in one of a number of possible reactions.  Such 
galvanic cells can be formed under colonies of bacteria on metal surfaces.  
Sulfate-reducing bacteria are often implicated here through their formation 
of ferrous sulfides.  This is a complex and not completely understood 
process.

Finally, there are some microbes that specifically oxidize metals to 
generate energy.  Thiobacilli and related organisms.  Iron is oxidzed by 
these bacteria.  Often these bacteria are used in mining operations to 
liberate iron and other metals from iron sulfide ores.  When colonies grow 
on surfaces, corrosion pits can form under them through the formation of a 
galvanic cell.

All that said, now the answer to your query.  The bacteria most likely to 
stimulate corrosion are the sulfate-reducing bacteria or the iron-oxidizing 
bacteria.  Both of these groups fall into the broad class of Gram-negative 
bacteria.  This means that their cell walls have a certain configuration and 
suggests antiobiotics to which they would be most sensitive.  Here is a list 
of compounds that may be effective against Gram-negative bacteria:  
streptomycin, ampicillin, methicillin, aztreonam, cephalosporins, 
carbapenams, tetracyclines, neomycin, gentamicin, chloramphenicol, polymyxin 
B, sulfonamides, and a host of others.  Sensitivity of a particular strain 
of bacteria to a particular antibiotic needs to be tested in the laboratory.  
There are a number of disinfectants that are generally bactericidal like 
Lysol, 70% alcohol, benzalkonium chloride, Listerine, etc.  Again, it is not 
clear that rust formation is microbially induced.  Corrosion is not rust 
formation per se.  It is the creation of pits or weaknesses in the metal, 
not really the oxidation of mineral surfaces.

I hope this helps.

Cheers,

Mark.