PRECAUTIONS FOR GALVANIZING CAST IRON PRODUCTS

Precautions for galvanizing cast iron parts mainly include the following points:

Thoroughly Remove The Oxide Skin:

the surface of cast iron will form a layer of non-conductive oxide film during high temperature casting, which will hinder the deposition of zinc-nickel alloy plating. Therefore, the oxidized skin on the surface of the work-piece should be thoroughly removed before plating, and it is recommended to use shot blasting machinery to polish the surface, which not only effectively removes the oxidized skin, but also enables the high carbon layer formed during casting to fall off, resulting in microscopic roughness, which is conducive to improving the bonding of the plating layer.

Adjustment of Current Density

The cast iron substrate has a loose and porous structure, with a large number of sand holes and uneven surfaces, resulting in a surface area much larger than the macroscopic area. Therefore, in the process of electroplating zinc-nickel alloy, the current density should be 1~2 times larger than other steel substrates, instantly activating the surface through the impact of high current, so that the loose surface is covered by dense plating layer.

Strengthen the Pre-treatment Process:

Since a large amount of contaminants such as grease, lubricating oil and freezing liquid will remain in the cast iron parts during processing, the pre-treatment process such as pickling and ultrasonic cleaning should be strengthened when plating zinc-nickel alloy to ensure the formation of a uniformly clean, conductive and easy-to-plated coating.

Avoid the Use of Pickling and Descaling Process:

For castings that need hot-dip galvanizing, do not use pickling and descaling process in pre-treatment. It is recommended to use sand blasting to remove the oxide skin on the surface, so that the surface can be basically cleaned of oxides and sand residues.

Adequate Preheating:

cast iron castings should be fully preheated before dip plating in the tank before going down to the hot dip galvanizing tank dip zinc, through the heating of the pores of the water vapor and other repellent, conducive to the infiltration of zinc liquid on the surface.

Through the above measures, you can improve the quality and corrosion resistance of cast iron parts galvanized to ensure the combination of coating and protective properties.