Sanding Grit / Primer Questions

[trukman1]

I took the bottom seat mount off because wet carpet rusted it BAD. Anyway, I had to file down the rust and am going to treat it with vinegar/water solution to neutralize rust in pores then skim with bondo. My question is what grit papers do I use to blend the bondo area to the painted area then scuff the whole thing so I don't get a line showing? I know this is pretty basic stuff but I thought I'd ask so I can get it right. This will be practice for more extensive bodywork later.
As long as I'm asking, can I use self-etching primer on the bare metal and over the bondo or should I use some other kind? I have some here so I thought I'd see if it can be used on bare metal and bondo.
Thanks for any and all advice.

 

[bp71k5]

I took the bottom seat mount off because wet carpet rusted it BAD. Anyway, I had to file down the rust and am going to treat it with vinegar/water solution to neutralize rust in pores then skim with bondo. My question is what grit papers do I use to blend the bondo area to the painted area then scuff the whole thing so I don't get a line showing? I know this is pretty basic stuff but I thought I'd ask so I can get it right. This will be practice for more extensive bodywork later.
As long as I'm asking, can I use self-etching primer on the bare metal and over the bondo or should I use some other kind? I have some here so I thought I'd see if it can be used on bare metal and bondo.
Thanks for any and all advice.

Depends on what kind of damage, but best plan is wirewheel the rust away... even the neutralized parts if you can. I try to get any filler as close to the finished surface as I’m applying it if at all possible. If you just have tiny pores in otherwise clean metal, skim the surface with a plastic trowel (or whatever it’s called) so the good metal shows through the filler and only the pores are filled. That way you don’t have to sand much of anything. Then just use sandpaper with grit rough enough to remove any material that’s too high but not so rough that you can’t use finer paper to remove any scratches from the previous sanding.

Long winded way of saying I start with ~220 and adjust up or down from there. I also wouldn’t blend bondo straight into paint. It should be blended to bare metal. You need to sand the old paint off several inches away from the damaged area and taper it off to nothing before you get to a paint edge. Then primer/ finish over that.

I also hate bondo and so my advice isn’t a professional opinion, just some experience.

 

[trukman1]

bp71k5, Thanks for the information. That helps a lot. I didn't have a clue about what sandpaper to use and didn't know about the bondo over paint thing. trukker1

 

[tenderfoot]

This is under your seat? I don't understand the Bondo under a seat thing. They make primer that's a filler too. It's been a long time but I think what we used way back when was called slick sand. Can any current body guys confirm slick sand still exists?

 

[bp71k5]

This is under your seat? I don't understand the Bondo under a seat thing. They make primer that's a filler too. It's been a long time but I think what we used way back when was called slick sand. Can any current body guys confirm slick sand still exists?

Yea, hard to picture what the damage is. Definately don’t use bondo to fix holes or compromised metal. Catalyze Glazing compound would be easier for pin holes or to fill surface scratches.

This should keep you busy reading, lots of great info from a professional.

https://ck5.com/forums/threads/ryokens-guide-to-rust-treatment-and-bodywork-101.283048/

 

[diesel4me]

I would wire brush the rust off as much as possible--sandblasting is the best way,it gets all the rust out of the pores,but not everyone has the means to do that..

Vinegar & water might help remove the rust that remains after wire brushing,but some might not get neutralized and come back to haunt you later--pure vinegar might work better,the water may work against you and encourage it to rust..they sell some better products like "Rust-Mort" or even Naval Jelly,or any of the many phosphoric acid rust converters and or latex based ones like Duro Extend that will kill the rust better..

I used to sell a product called "Feather-Fill" (by Evercoat) that is a sprayable primer sealer that is sandable and will build up and fill pits and other minor imperfections--if I remember right it uses a hardener ,so you must use it rather quickly before it starts curing,it forms a shell like coating and a lot of body shops liked it..
I looked on google,the stuff is still around,I last saw any about 20 years ago when I left the auto parts and body shop supply store..

 

[Maroon_Madness94]

X2 on the wire wheel with taking the rust away. I would highly suggest using a product to chemically treat the rust other then water and vinegar. I had a spray can of stuff I used but for the life of me cannot remember what it is called. On a side note why not just clean it up the best you can and use an encapsulator like por15? Or are you not putting carpet back in the truck

 

[trukman1]

X2 on the wire wheel with taking the rust away. I would highly suggest using a product to chemically treat the rust other then water and vinegar. I had a spray can of stuff I used but for the life of me cannot remember what it is called. On a side note why not just clean it up the best you can and use an encapsulator like por15? Or are you not putting carpet back in the truck

Putting new carpet in. Not a big fan of POR-15. I think I'm going to rust treat, epoxy prime, bondo and prime with regular primer then paint.

 

[diesel4me]

POR-15 worked well for me,I did the floor in my van with it 15 years ago,and lifting up the rubber mat ,it still looks great,no rust has returned even with it sitting parked over a decade outside..
Most backyard restorers make the mistake of sandblasting ALL the rust off--the stuff doen't work well on clean bare steel,it'll peel off after awhile..but on top of rust it is practically indestructible ..

I found POR-15 needs "some" rust to remain in order to work,it reacts with it and makes it turn into a black coating--the high gloss it has sometimes prevents topcoats from sticking well,but if left as-is it will also repel water better--it is not UV resistant though,it'll fade and turn chalky if exposed to sunlight for a long period..

 

[trukman1]

POR-15 worked well for me,I did the floor in my van with it 15 years ago,and lifting up the rubber mat ,it still looks great,no rust has returned even with it sitting parked over a decade outside..
Most backyard restorers make the mistake of sandblasting ALL the rust off--the stuff doen't work well on clean bare steel,it'll peel off after awhile..but on top of rust it is practically indestructible ..

I found POR-15 needs "some" rust to remain in order to work,it reacts with it and makes it turn into a black coating--the high gloss it has sometimes prevents topcoats from sticking well,but if left as-is it will also repel water better--it is not UV resistant though,it'll fade and turn chalky if exposed to sunlight for a long period..

I didn't realize POR-15 had metal prep. I may try that then topcoat with bondo or spot putty to fill in the rough areas then apply SEM color after priming. Thanks for the information!

 

[blazer74]

There’s also a silver primer for over the 15 so you can topcoat. Had good results. Follow prep and instructions.
Had it strip off in a few places where I got lazy.
Many don’t like it.

 

[trukman1]

There’s also a silver primer for over the 15 so you can topcoat. Had good results. Follow prep and instructions.
Had it strip off in a few places where I got lazy.
Many don’t like it.

Thanks blazer74, I went ahead and ground it down to bare metal, metal prepped and am going to prime and paint. Since I've bought a complete seal kit, that will hopefully keep it from coming back.

 

[Maroon_Madness94]

Being on the interior you should be fine for years to come. As I tell everyone it is all in the prep, do it right the first time and you won't have to worry about it.