Rust, Primer, Paint, Body Filler questions

[Zeeman]

I'm working on an old Craftsman tool chest, and some advice from you experts in body work please.
I need to be able to cover some lightly rusted/pitted areas with body filler. How do I do this right?
My metal is lightly rusted. I've removed most of the major rust, but there is some light rust in the pits, etc. I want to be able to put a thin coat of body filler over some fairly large areas of the sheet metal.
Do I use an epoxy primer, then body filler on top of that?
Does every bit of the rust have to go away? I doubt I can get it all shiny.
Thanks, and here's a few pictures of what I'm wanting to fill.

 

[mfrantz90]

You will want it cleaner than that...if you had access to a media blaster that would be best but if not a cupped wire wheel on a 4 1/2" grinder will do pretty well. No need to prime first just make sure your metal is clean and free of any oils. And mix little bits of filler at a time and mix it with a little extra hardener than they call for work quickly. good luck


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[Blake150]

There's a product called rust mort that is supposed to neutralize the rst on metal.wire wheel it to baste metal then use the neutraliser.filller then epoxy prime should be good to go from there

 

[Zeeman]

Thanks guys. I sanded with 100 grit first, then wire cup on 4.5" grinder. The cups I have are not knotted, and don't seem to get off more than what you see in the pictures. Would a knotted cup be better? Thanks.

 

[countryroad82]

You will definitely want to get that a little cleaner than what you have. Sometimes I have to go to a very fine wire brush to get into the pits. On things that don't seem to matter I am guilty of painting directly over top of that, but those are jobs that zero time is consumed into it. I was always taught that filler went over bare metal but in recent years I've changed my tune and now go over my primer in most cases. I've had bad experiences with rust convertors other than POR15, Chassis Saver, and the like so I don't buy into the stuff that's supposed to neutralize rust as a primer. Keep up the good work.

 

[Zeeman]

Thanks countryroad82. Are epoxy primers required for a job like mine if I get more of the rust off, or can I use something cheaper that will still allow the filler to stick? I plan to definitely get the paint out of the pores, and will try a finer brush. I appreciate the advice.

 

[Abeo]

if you want the rust to not come back, you have to eliminate it. Using a rust neutralizer (like Rust Mort, which I've used) only takes care of the top layer of rust... if there are flakes or scale, the rust will continue to grow.

I would personally blast the rust, using fine silica or crushed glass... the "fine" part is so you aren't too aggressive on the panel, and that you get to the bottom of the pits (having clean, bright metal). After that, it's a matter of putting on whatever filler over top of the panel, then epoxy prime/etc over that.

In a dry environment, you could get away with doing less... but if you put products over active rust, the rust will just come back. I saw it time and again at the collision shop I worked at back east.

 

[Botje]

I would use acid to remove the rust, neutralise, then primer, then filler.

Wire brushing, imho, is only good for removing part of the rust. To get it perfect takes too long for me, so i switch to acid or media blasting. And if it isnt spotless, no rust, after wire wheeling, chances are the rust will come back. Rust that has been wire wheeled cant easily be soaked by the rust stopping primers. At least thats what ive learned and seen over the years.

 

[Zeeman]

What type of acid, citric? And what would you neutralize with. Thanks.

 

[Botje]

I used Phosphorous acid, it is easier to find here.
Things like Evaporust are easier to source stateside, not sure what the main ingredient is.

 

[Kevin54]

Over epoxy primer or over bare metal has always been up in the air for the last few years. I use RAGE body filler, and it recommends roughing up the metal, and applying directly over bare metal, I put it over metal that has been sanded with 80-100 grit paper.

 

[Nor'Easter]

For a toolbox you can probably get away with filler over bare metal.

Wouldn't dare do such a thing on a vehicle, filler is porous and does not aid in corrosion resistance.

 

[Zeeman]

I used Phosphorous acid, it is easier to find here.
Things like Evaporust are easier to source stateside, not sure what the main ingredient is.

Thanks. I talked a friend of mine to let me use his bead blaster, and he has some media that is like flakes as he described them.

 

[Zeeman]

For a toolbox you can probably get away with filler over bare metal.

Wouldn't dare do such a thing on a vehicle, filler is porous and does not aid in corrosion resistance.

Thanks. I guess I'm still confused over whether the common practice in using filler is to prime then fill, or fill then prime. Yep, it's just going to stay in my garage, so it's not going to be exposed like a car. I still don't want it to mess up though, if you know what I mean.

 

[Zeeman]

Over epoxy primer or over bare metal has always been up in the air for the last few years. I use RAGE body filler, and it recommends roughing up the metal, and applying directly over bare metal, I put it over metal that has been sanded with 80-100 grit paper.

This is what I've done in the past, but then I've read that some people use the primer first, then filler.

 

[97nismo]

Always heard you get down to clean bare metal, filler then acid etch primer so if it chips rust won't spread

 

[RW-7]

Most Body fillers on the market today are DTM (Direct To Metal) and can be applied to bare metal. Save yourself some money and skip the Epoxy Primer.
Be sure and treat that metal once you have removed all the rust. You can coat the area with a rust inhibitor, or convertor. Let that cure, clean very well, and use your filler. Prime, and paint. Good luck!

 

[gahrajmahal]

A vehicle exposed to the weather in Georga might rust if not cleaned better than you have done, but since this is in a garage with most, exposure to high humidity would probably never have a problem. There are some products from Eastwood, like metal wash that leave a phosphorous coating on the bare metal. I used to use 3M metal prep, which is like a diluted muratic acid which you then rinsed with water to neutralize. I think primer then ez sand or something heavy would fill those pits, no bondo needed. Keep us informed with your results.

 

[FunkyfullWidth]

Get one of those small hand held blasters. Here's one at east wood just as a reference.

http://www.eastwood.com/speed-blast...4-pWD0nuWI5w25dMFhV80IoTJQs5eNdwyNRoCEmXw_wcB

no experience with that one. There's a bunch of them out there. I used one once, I believe it was a blue point. Worked good for small jobs. Like real small.

 

[K13]

The common practice for body filler is over bare metal. That is the way every body shop does it. The only time it gets put over epoxy in the real world is during restorations where a car is epoxy primed after being stripped. You will be fine either way as long as you get primer/paint over the filler in a relatively short period of time. If it is going to sit with just filler for any length of time put an Epoxy underneath but make sure it is fully cured before you put the filler on as polyesters will react with uncured epoxies.

 

[Zeeman]

Thanks for the info K13. I sandblasted it, but all the rust and paint did not come off. I would say 90 percent is bare, shiny metal. It will probably be several months before I can paint the finish coat on it. I could just fill it, then primer, then take inside til it gets warm enough to paint. What do you think about that?

 

[bgarrett]

I have been fighting rust on 1930s and 1950s cars for almost 50 years. The best method I know is to follow directions for POR15 and prime while tacky.

Dont take advice from professional body and paint men. They have different goals in life---they only care about - make it look good quick and sell it while you want it to last forever

 

[Nor'Easter]

Dont take advice from professional body and paint men. They have different goals in life---they only care about - make it look good quick and sell it while you want it to last forever

Yikes, that's painting with a pretty wide brush if you ask me. Not all of us are in the insurance game.

 

[sanddan]

A few things to keep in mind.

Epoxy primer/sealer like DP40 is not intended to be sanded. It should be used as a base and top coated with a 2 part sanding filler/primer. For DP40, it can be top coated for up to 1 week, if longer it has to be sanded before top coating. From experience it dries very hard and loads up sand paper when sanded.

For your project (tool box that will always be out of the weather) any filler/primer that's intended to be sanded will work fine. For light rust like you show 2-3 coats with a high build primer would likely fill the imperfections and when sanded give you a ready to paint surface. I'd try that first before resorting to filler.

 

[madoc1]

evaporust is just that and works great. on a flat surface you need to use an old towel or something to keep it in contact with the metal. i have also used ospho, available at ace hardware and other places. it converts the rust to a black substance you can then sand off. the idea of using a good high build primer and sanding between coats should give you a good base for finishing is the best way to go if there are no deep depressions. good luck

jim

 

[edl]

macdoc1 - what sort of paints did you use over ospho?

i have two projects, one uses a sherwin williams industrial single stage lacquer and the other i am using ppg alk-200 (without hardner) - like the op, the machines i am refinishing have pits and you can never get all the rust out

ospho advertises itself as converting rust from iron oxide to iron phosphate - they say you can paint right over that...but i wonder what happens to the phosphoric acid? - does it convert to something else? - or is the idea that it is so thin (like water), the amount is irrelevant to the top coat?

thanks!

 

[countryroad82]

I have been fighting rust on 1930s and 1950s cars for almost 50 years. The best method I know is to follow directions for POR15 and prime while tacky.

Dont take advice from professional body and paint men. They have different goals in life---they only care about - make it look good quick and sell it while you want it to last forever

Ouch!

 

[BORING HOP YARD]

Greetings.
I use Rustmort and prep and tech from home depot.
I apply with a paint brush, let is sit, scrub with wire brush, re-apply over and over until all of the rust is gone. It looks like fresh metal that has rust pits cast into it.
Then I take a spray bottle of strong degreaser and spray the area being treated and scrub the area. I then pressure wash the part if it has any seems. then its right into blowing every nook and cranny with clean air and towel drying until the part is completely dry. I use CRE-X21 Series epoxy Primers when I etched parts and SPI epoxy when I don't etch.

 

[edl]

thanks BHY

anyone on the ospho questions?

thx

 

[mmouse]

ospho advertises itself as converting rust from iron oxide to iron phosphate - they say you can paint right over that...but i wonder what happens to the phosphoric acid? - does it convert to something else? - or is the idea that it is so thin (like water), the amount is irrelevant to the top coat?

thanks!

Ospho will leave an acid film. Epoxies will not adhere over the acid film. To remove the acid film, wet it with ospho, and while active (don't let it dry) scrub with scotchbrite and rinse with water. Most people call this "nuetralizing", but you are really diluting and rinsing the acid away while it is active. You must be super meticulous. Miss one spot, and you may get a blister or bubbling. Since the clean up after acid must be perfect, I won't use it for autobody. For indoor home or shop projects it will probably be fine.

 

[sberry]

I have been fighting rust on 1930s and 1950s cars for almost 50 years. The best method I know is to follow directions for POR15 and prime while tacky.

Dont take advice from professional body and paint men. They have different goals in life---they only care about - make it look good quick and sell it while you want it to last forever

There is SOME truth to this.

 

[BORING HOP YARD]

Your should look for a primer that will work with a surface treatment
Here is a clip from the CRE-X21 Series epoxy Primers data sheet.
A chemical treatment (or conversion coating) on non-sandblasted substrates will improve adhesion and performance properties of the finished coat.
I personally would never use a product that I apply, let sit and then apply primer. I have spent to much time and effort getting it to that point, I'm going to do everything I can to never have a problem. Washing with soap and rinsing with water is no big woop. I go the extra with a pressure washer because its in my shop, takes about a minute to set up and go.
Greg

 

[edl]

thanks

so even though ospho's directions say to not rinse it, to let it dry overnight and to paint directly over it, you guys who use it do not do that and instead rinse if off?

has anyone used it as per the instructions with success? - is the only issue with epoxy paints?

 

[BORING HOP YARD]

Do yourself a favor, When you have a chance to do some reading, go to google and search (ospho's primer issues) this was enough for me to steer clear of it.
Rust mort will also get a white powder and if its left to dry with out being rinsed and that will cause paint not to stick as well. I have seen this first hand
I have never used Ospho's so this is where my advise ends.
Good luck in your quest.
Greg

 

[don long]

I have been fighting rust on 1930s and 1950s cars for almost 50 years. The best method I know is to follow directions for POR15 and prime while tacky.

Dont take advice from professional body and paint men. They have different goals in life---they only care about - make it look good quick and sell it while you want it to last forever

There is SOME truth to this.

Now you guys have my attention. I could certainly argue with these statements
having owned and operated several bodyshops in my career and have seen those butchers you speak out about but our industry shouldn't be judged by the few. There are many more quality minded techs in our industry than those money whores you refer to.

I to restore old rusted things and usually blast the piece first then apply a thin coat of body filler over the bare metal. If I can't get to it after blasting like a large piece I will apply an epoxy primer to it only to prevent it from rusting again before I can finish the project. Body filler will adhere to primer if it is sanded properly

 

[Zeeman]

Thanks for all the advice and comments. I ended up media blasting most of it in a large cabinet, then cleaned it well and used body filler/putty. Then, I degreased again and primed/painted. Here's a few pictures.