Undercarriage question

[truckinman466]

If I am going to undercoat the car, do I need to put finish coat on or can I seal and prime it and undercoat?

[jimynick]

if by "undercoating" you mean rustproofing, I'd paint the car and then rustproof it. Doing it the other way around you stand a chance of having the rustproofing/undercoating contaminate the substrate which may pose a problem when later painting the car. but then, that's just my 

[JS29]

 

[Burdar]

I think he's asking if he can undercoat over primer instead of fully painting the underside first.  The factory never fully painted the bottom with exterior color.  They undercoated right over primer.  So...paint the exterior body and then undercoat but you don't have to fully paint the bottom with color first.

[RUNCHARGER]

The original primers would soak up moisture, not sure about new primers. I believe you are better off to paint it to seal out the moisture and then undercoat over the paint.

[jimynick]

The original primers would soak up moisture, not sure about new primers. I believe you are better off to paint it to seal out the moisture and then undercoat over the paint.

Yep, what the man said. Unless you're one of the "the factory never painted the bottom" guys and are afraid that'd cover some of your chalk marks! 

[JS29]

Urethane primer's are not pores. But I think even a shot of single stage before undercoating would be the way i would go.   

[jimynick]

Urethane primer's are not pores. But I think even a shot of single stage before undercoating would be the way i would go.   

  Yep, that's the way I went, too. 

[truckinman466]

Ok, thanks guys. I think I'll go ahead and put some finish coat on before I undercoat.