Topic: Pretreatment of MS susbstrates

We are having following process for phosphating of MS / GI substrates.

Degreasing, Rinsing, Derusting, Rinsing, Hot phosphating, Rinsing, passivation.

Here I want to know; is passivation required before powder coating process also.

As passivation actualy passivate the surface or we can say it makes the surface inactive which is desired after phosphating as that time surface becomes charged and prone to corrosion.

So to delay this corrosion; passivation is done.

Now coming to powder coating; should we follow passivation also after phosphating.

Please help.