The outside spray zinc wire of ductile iron pipe is carried out when the ductile iron pipe temperature drops to about 200 ℃ after annealing.
The application of spraying zinc wire:
1. Due to the lower electrochemical potential of zinc than iron, the ductile iron pipe is protected from corrosion by the reaction of zinc, that is, zinc corrosion is preferred to iron corrosion.
2. When the zinc layer is corroded by the salt solution, insoluble compounds such as zinc phosphate, zinc chloride and zinc sulfate will be produced, covering the outer surface of the pipe, thus slowing down the corrosion progress of the pipe.
Principle of spraying zinc wire :
The zinc spraying process generally adopts thermal spraying method, that is, the zinc wire is heated to the melting state during spraying, and then, with the help of compressed air, the melted zinc is sprayed into the atomization state, and the state of tiny zinc droplets is sprayed on the outer wall of the ductile iron pipe and adhered to it.
Precautions during zinc spraying:
1. Pay attention to dustproof during spraying. Operators of zinc spraying equipment must wear protective masks or masks during operation.
2. The zinc coating shall cover the entire outer surface of ductile iron pipes without any defects such as exposed spots or weak adhesion, otherwise it will easily cause corrosion concentration in the defects.The weight per unit area of zinc coating should not be less than 130g/m2.
