- the thickness of the plating layer is different
Hot-dip galvanised coating is generally thicker zinc layer, about 40μm or more, or even up to 200μm or more, hot-dip galvanised layer is generally 10 to 20 times the electro-galvanised zinc layer.
The electro-galvanised zinc coating is very thin, about 3～15μm, and the weight of the coating is only 10～50g/m2.
- the amount of zinc plating is different
Hot-dip galvanised sheet zinc plating is not too small, generally the smallest double-sided 50 ~ 60g/m2, up to 600g/m2.
And electric galvanised sheet of zinc coating can be very thin, the minimum of 15g/m2, but requires a thicker layer, then the production line speed is very slow, do not adapt to the process characteristics of the modern unit, the general maximum of 100g/m2. Because of this, the production of electric galvanised sheet is greatly restricted.
- the plating organisational structure is different
Hot galvanised sheet of pure zinc plating and steel plate substrate between a layer of slightly brittle compounds, pure zinc plating layer crystallisation mostly form zinc flowers, plating uniformity without porosity.
The zinc atoms of the electro-galvanised layer are only deposited on the surface of the steel plate precipitation, and is physically attached to the surface of the steel strip, there are many pores, very susceptible to pitting due to corrosive media, so hot galvanised sheet is more corrosion-resistant than electro-galvanised sheet.
- heat treatment process is different
Hot-dip galvanized sheet is generally cold hard plate as raw material, continuous annealing and hot-dip galvanizing in the galvanizing line, the steel strip is heated and cooled after a short period of time, so the strength and plasticity are affected to a certain extent, and its stamping performance is worse than that of the same cold hard plate degreased and annealed by a professional production line of cold rolled sheet. Hot-dip galvanised sheet is cheaper to produce, has a wider range of applications and has become the main variety of galvanised sheet market.
Electric galvanised sheet to cold rolled sheet as raw material, basically to ensure the same processing performance of cold rolled sheet, but its complex process also increased production costs.
- different appearance
Hot-dip galvanised layer surface is rough, bright, serious zinc flower;
Electro-galvanised zinc layer is smooth and grey (hair stain).
- the scope of application and process differences
Hot-dip galvanising is suitable for large parts and equipment; hot-dip galvanised sheet is the first steel pipe is pickled, in order to remove the iron oxide on the surface of the steel pipe, after pickling, it is cleaned by ammonium chloride or zinc chloride aqueous solution or ammonium chloride and zinc chloride mixed aqueous solution tanks, and then sent to the hot-dip galvanising tank.
Electro-galvanising is suitable for small parts. Electroplating solution is used and positive and negative electrodes are applied to the steel plate and electroplating solution respectively.
