Just a quick answer for #2:
Stainless steel - typically most spendy, will likely outlast the wood they are placed in. If you want a 'show' hive this might be the way to go. Uneconomical otherwise.
Hot-dipped galvanized (HDG) - regular steel (also referred to as carbon steel or mild steel) that has been dipped in a bath of molten zinc, leaving a heavy coat of zinc on the surface. Zinc acts as a sacrificial coating; over time, rather than the steel rusting, the zinc does. The zinc just doesn't look bad when it rusts.
Electro-plated or electro-galvanized or zinc plated or zinc-electroplated - carbon steel that has been dipped in a bath containing zinc ions. An electric current is passed through the metal, which chemically deposits zinc on the surface. The same effect as hot-dipped galvanized, but the coating looks better and lasts half as long (or less).
Cement coated - carbon steel coated with a non-corroding material. Works great when the coating is intact. . .
Aluminum - not as corrosive as steel, but will still 'rust' given enough time. Spendy, and difficult to hammer in without bending - the material is typically softer.
Bottom line - HDG is probably the best matched material for the life of the wood they are hammered into. Cheaper than stainless, but last longer than others. Other than the issues of finding 7d, readily available.
Stainless steel - typically most spendy, will likely outlast the wood they are placed in. If you want a 'show' hive this might be the way to go. Uneconomical otherwise.
Hot-dipped galvanized (HDG) - regular steel (also referred to as carbon steel or mild steel) that has been dipped in a bath of molten zinc, leaving a heavy coat of zinc on the surface. Zinc acts as a sacrificial coating; over time, rather than the steel rusting, the zinc does. The zinc just doesn't look bad when it rusts.
Electro-plated or electro-galvanized or zinc plated or zinc-electroplated - carbon steel that has been dipped in a bath containing zinc ions. An electric current is passed through the metal, which chemically deposits zinc on the surface. The same effect as hot-dipped galvanized, but the coating looks better and lasts half as long (or less).
Cement coated - carbon steel coated with a non-corroding material. Works great when the coating is intact. . .
Aluminum - not as corrosive as steel, but will still 'rust' given enough time. Spendy, and difficult to hammer in without bending - the material is typically softer.
Bottom line - HDG is probably the best matched material for the life of the wood they are hammered into. Cheaper than stainless, but last longer than others. Other than the issues of finding 7d, readily available.