The product used for "saturating" rotten wood, is called "Get Rot" and often used in boats !!
The only real way to do rotten wood, is to remove it, but "Get Rot" does help in instances where removal is not possiable!!
This product, is actually just a thin epoxy resin, used to saturate the old wood, but the wood must be completely dry to work effectivly and usually holes are drilled into the wood, then the get rot is forced into the holes with a "squeez bottle", saturating the old wood..
Termites and carpenter ants are quite different from rot but both need moisture, insects are pretty easy to get rid of , by saturating the wood with a product containing Cuprous oxide, this being the green coating..
There used to be a product called "Termin-8" and another called "Cuprinol" but I,m not sure if either product is still available, as the EPA has outlawed many of these products..
Good luck with your indevour, Bill H...