The hot-dip galvanized nut is matched with the hot-dip galvanized bolt, that is, the reaming nut is subjected to hot-dip galvanized surface treatment. Because hot galvanizing is coated with zinc, reaming is necessary. Hot galvanizing is characterized by unsmooth surface but strong corrosion resistance. It is generally used outdoors and has 4.8, 8.8, 10.9 and 12.9 high strength grades.