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Corrosion resistance of crystalline zinc phosphate coating

I am an in charge of an industrial paintshop. we are using stoving synthetic enamel for protecting small mild steel chassis type of fabricated jobs. We are using seven tank pretreatment (hot process) before painting. After the pretreatment we are achieving a crystalline Zinc phosphate coating of 1.1 to 4.4 gm/m2 on mild steel which has matte finish & grey in colour. what is the maximum time after phosphating ,in hours after which I can spray the primer coat? which is the desirable period in which primer is to be applied to get the best results?
This question is being asked since we are encountering some situations, wherein we are not in a position to spray primer immediately after phosphating.

Rmaesh Babu Pagadala
Paint shop Incharge - Hyderabad, Andhra Pradesh, India
August 21, 2008

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Dear Ramesh,

Generally it is advised to paint within 24 hours of coating. Thats the maximum time limit. even then if you observe any red marks within 24 hours
it means your PT is not good enough.

Regards

S.V. Aurobind
plating process supplier - Bangalore, India
October 10, 2008