rust treatment before paint

[bing_kee66]

i intend on having my car properly  painted in a few months, however the previous owner went a little crazy with a sander and left the car with a handful of areas with surface rust.  my question is, what can i do now to treat the rust that wont have to be redone or create a problem(i.e. more work) when it comes time to paint. im planing on using por15 on the engine bay/underside/floor pans, can i use it as a body primer? or will a product like  Rust-Mort hold for a few months or will i have to cover it? 

[Crashtd420]

Are you talking the external body panels?

If you are I wouldnt use it for what your talking about.... once the por 15 is dried its extremely tuff to sand.... plus if its just random spots, those will make the other layers of paint inconsistent.....

 

I actually encased my entire 521 in por15, body panels, Inside and out plus all the frame components.... it can be used as a primer but it was a pain to spray and work with.... I did a garage paint job, no body work, just removed old paint down to bare or semi rusty metal,  coated  with por, then a top coat.... anywhere that isn't exposed to the sun doesn't need that.....

They do make a metal prep and other products that remove rust....

 

Personally I would talk to who ever is going to paint it.... you may cause them more work by trying to apply something.... 

But it's good to use everywhere else...

 

[bing_kee66]

yea body panels. its more than a handful of spots of rust, that was underestimation, if i were to por15, id do the entire car. how did your truck turn out? so i should treat the rust and leave it as bare metal?  also can i apply bando in advance or does that absorb water the same way primer does?

[Draker]

I would use metal prep to get it neutralized then spray epoxy primer over it.

[tr8er]

Bondo causes rust.  Epoxy primer over metal.  Than bondo if you must.  Por15 is awesome stuff, but can be a big issue on thin metal.  If it flexes, it cracks, it will allow moisture between the paint and metal.  So best for metal that won't flex like chassis and frame.  But I still use it all over the place and love it almost always.  

[bing_kee66]

5 minutes ago, tr8er said:

 bondo if you must.

 

 the bondo is for dings a scratchs nothing crazy. 

 

it didnt seem right using por15 on the body but i heard that its been done.  ill look into epoxy primer, thanks for the advice guys

[Crashtd420]

9 hours ago, bing_kee66 said:

 

 the bondo is for dings a scratchs nothing crazy. 

 

it didnt seem right using por15 on the body but i heard that its been done.  ill look into epoxy primer, thanks for the advice guys

Yes look into the epoxy primer.... probably a lot easier to work with...

This was my first paint job so I had a lack of knowledge and a learning curve to deal with... 

The biggest reason I wouldn't is because it's really hard to sand once dry.... It did spray on pretty smooth so overall my finish is smooth.... My paint job came out good but I honestly regret doing the por 15 all over.... just a real pain to work with..... but once I started I wanted to continue for consistancy....

Dry time is long, and spraying is a pain... you need to constantly clean the gun.... the stuff is best left to floors, firewalls and chassis ... 

[bing_kee66]

might have been a pain in the ass, but your truck turned out nice from the looks of it. 

 

 ive settled on this , i dont have a large enough compressor to use a gun, and its mostly patch work

[Crashtd420]

7 hours ago, bing_kee66 said:

might have been a pain in the ass, but your truck turned out nice from the looks of it. 

 

 ive settled on this , i dont have a large enough compressor to use a gun, and its mostly patch work

Thanks for the compliment..... 

It's not show quality but I was never going for that.... its rust proofed and there is no bondo, and dont care about the dents, it's a truck, it adds character.....

 

And with what your trying to do the spray cans will be a lot easier to deal with... 

 

I actually did all my paint with I think a 50 gallon compressor... had the compressor set to the max and the gun had it's own regulator so that was set low to the gun and paint spec.... the only problem was I just couldn't stay on the trigger a long time..... 

Just remember it's all about the prep work, it will show, .. goodluck.... 

 

 

[rosso]

What about using Gempler's Rust Converter or Rust Sergeant from RCMP? Both will convert any rust to Zinc or some other oxide and work as a primer that you can paint until you are ready to have the whole car painted.

 

I have not tried this on body panel, but the rust converters work great for converting rust on chassis and then simply painting with a black enamel. I have some and will be using it on some spot rust on body panels on the 510 goon project. I'll post pictures when I get to it next month.

[bing_kee66]

i will test it out,  i curious how well it will sand down

[DanielC]

You cannot convert rust to zinc.  Rust is a compound of the chemical elements iron, and oxygen, zinc is another chemical element.  Rust converters typically contain phosphoric acid, and can convert the top most layer of rust to a compound of iron, phosphorus, and oxygen. 

The products mentioned above may have some zinc in them. 

 

Rust is an electrolytic reaction.  That means you have to have two or more different materials, and an electrolyte.  Water is the electrolyte, the carbon in steel alloys and the iron are the two different materials.  

Different metals have a different electrolytic potential.  They make a battery.  For example, if you put a piece of zinc and a piece of copper in lemon juice, the zinc is corroded, or used up to make electricity.

 

The problem with rust is that once rust starts, the rust has a lower electrolytic potential than the iron, and rust then increases the rate of rusting.

 

Zinc is used to prevent rusting because it has a higher electrolytic potential than iron, and the zinc corrodes, protecting the iron, until the zinc is gone.

 

The way to prevent rust is to seal the steel from water, and air.  I believe this is best done with an epoxy primer.

 

[rosso]

Daniel,

 

Regarding Gempler's I guess I should have said "Chemically converts rust into an inert, black barrier." but I thought I had seen a rust converter that mentioned zinc. My poor memory, thanks for the clarity.

 

I'm not sure how it all works, but Gempler's say it functions as a primer and can be painted over. I plan to use it on my frame and running gear then paint.