The Stovebolt Site Forums The Shop Area Paint and Body Shop Old and New Enamel, and a Durability Test

Now I know everyone has some sort of an idea or guess or supposition or theory but I’m looking for the real reason, like a scientific explanation of, why is rattle can enamel not as durable or hard as the original paint?
I’ve spilled gas down the side of the factory Mariner Blue paint of my 1950 truck dozens of times and it seems to have no effect on the paint. She was top coated by an amateur painter many decades ago with fire engine Red for her duty as, a fire truck. That had just about every problem that one could possibly encounter with a paint job, i.e., drips, sags, wrinkles, dry spots, fisheye and over the years has now gone flat. It is also pealing from the old original paint in many spots from an ill prepared surface. Yet gasoline seems to have no affect on that paint either.

Now I had the running board sandblasted last year and painted them with several coats of Rustoleum rattle can enamel paint. So the paint has had nearly a year to cure now.
Last week I was topping her off with that cheap $3.79 gas, in anticipation of some $4.00 a gallon Labor Day gas. Like an idiot I drove it straight home and parked it in the warm garage, which is attached to the kitchen. I kept smelling gas all afternoon but that is not unusual since she always smells bad after we come home from our exercise. Later in the day I went out to get a tool off the bench and I noticed a small puddle on the floor. Thinking that the durn puppy couldn’t hold it and had soiled my garage floor I grabbed the paper towels, twern’t pee! The cool 55° gas had expanded in the 70° garage and had run down and filled the ridges in the front half of the running board. The paint was blistering up like I had applied a stripper to it.
So that’s the question, what is the difference between this enamel and the other two that are on the cab?
Denny Graham
Sandwich, IL

Ive also pondered this one, rattle canned a few old dirt bike tanks for teh boys and they look great till they get gas spilled on em and the paint is ruined.
Would it be the hardner that is added in the factory paint???
Tim

There are some pros here that can expand on this but in the mean time I'll take a shot.

I suspect the last paint job was lacquer. Lacquer can soften with any number solvents. it's not very resistant. In fact even a damp rag can cause a white haze.

Keith

Enamel hardener is a relativly new compound, I don't think the the enamels of 40, 50 or 60 years ago used a hardener. They were thined with an enamel reducer and simply cured by oxidation. That was why they forced dried them with heat ovens at the factorys and better paint shops. Generally in the body and paint shops it would take over night (24hrs) for the paint to set up and around a month before you could wax or clean it. Also the older enamels gave you a high gloss and they were not rubbed out like a lacquer job. If you tried rubbing them out with a buffer you killed the gloss.

Rustoleum is enamel keith, not lacquer. And the old paint, factory and repaint holds up just fine gasoline doesn't touch it.
Also the AD trucks were painted with enamel and the cars with lacquer back then.

Denny G

Boy Denny,
you opened up a discussion I am interested in ..the WHY is some thin i would like to know.

Well Tim there are obviously different flavors of "enamel” to day. I've used Rustoleum for general protection for tons of items literally for decades and always had good luck with it. They’ve come out in the last couple of years with hundreds of different colors and textures, my Home Depot has a whole isle just dedicated to Rustoleum now. I’ve use the semi-gloss for all the under hood and under frame stuff and haven’t noticed any of it lifting or blistering. Which reminds me, what sort of magic paint does Eastwood use that justifies the doubling or tripling in price over hardware store enamel.
The newer spray enamels are act more like lacquers in that they go on thinner, dry a lot faster and don’t seem to have that glossy look that the old enamels had.
I was hoping that one of our paint gurus would chime in with some facts that we could sink our teeth into.
All of the rattle can paint that I use I either dry in the wife’s oven (don’t ya tell her now) or if it’s to big of a part I set up a few halogen lamps a few inches away and under the part and let it cook over night, that usually gets the part up to around 130° or 140°.
Denny Graham
Sandwich, IL

Denny,

Here in Southern California I just put the parts out in the sun. After awhile the parts are so hot you cannot touch them. Natures oven.

I am also interested in this. I primed a bunch of frame parts with Rustoleum Professional primer about a month ago. It is still what I would call "not dry". When it is sanded the paper loads with paint. I tested a spot with paint thinner "mineral spirits" and in a matter of seconds the primer was gone to bare steel.

Tomorrow I am going to do a "gas test".

The results to come.

Well guess what, the gas took off the primer as fast as the paint thinner.

This is off the Rustoleum web site under FAQ

Q Which product has the best resistance to gasoline?
A Only EPOXYShield Garage Floor Paint has gasoline resistance.

Sounds about right, but the question still remains, what's the big difference between the old and new enamels. It sure wasn't epoxy back in the early 50's.
Denny G

There are several types of enamel. Enamel paints are really just a group of paints that share a characteristics of crosslinking as it hardens and not being significantly softened by the solvent that originally bore them once try, and that they are hard and glossy like the vitreous fired enamel you find on appliances.

Early auto enamel paint was oil-modified polyester, later enamels are acrylic or latex based. Rustoleum "Enamel" shares very little chemistry with the real, old style polyester enamels. The gasoline is actually softening and breaking the crosslink. I can't figure out what is actually in today's Rustoleum (they changed the formula recently), but I suspect its probably latex based, which is softened by gasoline quite easily.

Lacquers don't crosslink like enamels, but they may also be gasoline resistant as long as the pigment doesn't loose adhesion from it.

I going to rethink the Rustoleum use on the chassis parts. Always had good luck with it before, but like 4ontheFloor said; Rustoleum has changed. I am going to get some Krylon and check it out. I always used their engine enamels with good results.

Check out this Krylon paint comparison chart.

Paint comparison chart

Very interesting Josiah, in all these years that I've been using spray paint I never new they were packaging it with Latex enamel. I was always under the impression that it was an oil based enamel. In this case though I don't think it is a water based Latex, if it were spraying it on bare metal would cause it to rust under the paint film and I've never seen that on any rattle can paint that I've used.

Good chart Lonnie, I printed it out, something more to add to the pile.

Denny Graham
Sandwich, IL

Most of the latex enamels aren't found in rattle cans, most of those are house paints. However, latex doesn't necessarily have to be water based, it just usually is.

There are some recent rattle can latex enamels, as Lonnie's chart shows, and latex and acrylics are often combined in the same paint.

The good rattle can paints are acrylic oil based, but
Rustoleum is something weird and they have a secret formula. I think Rustoleum is an alkyd enamel.

# Vitreous enamel, a smooth, durable coating made of melted and fused glass powder.
# Enamel paint, a paint that dries to an especially hard glossy finish, resembling vitreous enamel,
paint that supposedly dries to an extremely hard, usually glossy, finish. In reality, most commercially-available enamel paints are significantly softer than either vitreous enamel or stoved synthetic resins.

With respect to paints enamel is a fanciful term, implying that an ordinary latex or oil-based paint has the same properties as true, fired vitreous enamel.

Some enamel paints have been made by adding varnish to oil-based paint.

The term sometimes refers to oil-modified polyesters that were introduced in the early 1930s. The oil is required to stop or enhance the crosslinking of the paint in order to achieve sufficient flexibility of the paint film.

Typically the term "enamel paint" is used to describe oil-based covering products, usually with a significant amount of gloss in them, however recently many latex or water-based paints have adopted the term as well. The term today means "hard surfaced paint" and usually is in reference to paint brands of higher quality, floor coatings of a high gloss finish, or spray paint

i think it depends on the paint i got some napa spray can for a motor bike and gas wouldnt melt it painted my sons car added a hardner its gas proof but yes some paint gas will melt or dull the finish

What I'm wondering is are there any enamels now that are as good as the old ones ?
I know Rust olem is different than it was back in the 70's although I can't get them to admit what they did to change it. Todays RustO drys faster to the point of making it hard to keep a wet edge if I'm brushing when its warm. Doing it in the sun is real hard. Plus its not as easy as it was to keep a can of paint. It thickens up and I've bought a few cans that were thick right off the shelf.
Old RustO used to separate leaving the oil on top,now it just drys over the top and left long enough will be a thick dry cover over the top of the paint.
A tidbit-- I questioned GM back in the 60's as to how the lacquer they used would end up with a shine. I could never figure out how they got the door jams shinny as I always had to buff a shine into lacquer.
They said they used a sightly different lacquer and sprayed it hot.
Dan

thats a lot of information. my brain hurts.