Summary for pvc coating on galvanized wire Discussion
PVC coating on galvanized wire is the central issue here: JanapaReddy VinodKumar reports that 25.5 swg low-carbon, low-silicon wire with a 25 gsm hot-dip zinc coating looks fine before coating, but after PVC coating at up to 150 °C the zinc appears to be removed and black spots show up on the GI wire. The thread excerpt does not include any replies or diagnosis, so no specific cause or remedy is given in the source text. Based on the question alone, the problem seems to be a post-PVC-coating surface defect or adhesion/heat-related damage, but the archive excerpt provided does not contain an answerer’s explanation. Any conclusion beyond that would be speculative.
Q. We are using hot dip galvanization for galvanizing 25.5 swg low carbon low silicon wire.
The Zinc coating is 25 gsm. There are no white spots or black spots on the wire. But after PVC coating if we check the wire the zinc coating is getting removed from the wire. There are lot of black spots appearing on the GI wire after PVC coating. We are not able to find the reason. The PVC coating is done at a maximum of 150° C temperature.
Kindly please explain the reasons behind this and suggest so that there is no peeling of zinc after PVC coating.
JanapaReddy VinodKumar
working as Manager(production) in a wire galvanization unit – Hyderabad, AndhraPradesh, India
February 7, 2012