Compared with the galvanizing pad, the zinc layer on the surface of
the galvanizing pad is thick, with strong adhesion, and the zinc
layer is not easy to fall off. Generally, the thickness of the
galvanizing layer is 5-15 μ m, while the hot galvanizing layer is
generally more than 35 μ m, even up to 200 μ M. The coating is
compact and free of organic inclusions. As we all know, the
mechanism of zinc's resistance to atmospheric corrosion includes
mechanical protection and electrochemical protection.
Under atmospheric corrosion conditions, there are ZnO, Zn (OH) 2
and basic zinc carbonate protective films on the surface of zinc
layer, which can slow down the corrosion of zinc to a certain
extent. This protective film (also known as white rust) will be
damaged and form a new film. When the zinc layer is seriously
damaged and endangers the iron matrix, the zinc produces
electrochemical protection on the matrix. The standard potential of
zinc is - 0.76v, the standard potential of iron is - 0.44v.
When the zinc and iron form a micro battery, the zinc is dissolved
as an anode and the iron as a cathode is protected. Obviously, the
resistance of hot-dip galvanizing to atmospheric corrosion is
better than that of electro galvanizing.