Does rust have to "breath" to live?

[GreeCguy]

Kind of a weird question, but here we go.

Early this year, I rebuilt my BBQ grill which I made from a 55 gal metal barrel. I burnt it out and then painted it with flat black BBQ grill paint. However, even with two coats, it started rusting in about a months time. Shortly after that, I had some used cooking oil from one of our fish fries and I poured that oil over my grill, (as well as coat the inside of the grill) and since then, there's not a spot of rust on it. It was just getting to the point of wearing/cooking off so today, I coated it with another coat of used cooking oil from another family fish fry.

It got me to thinking, does rust have to "breath" in order to "live." Other than creating a pleasing odor while cooking on my grill, (it smells like fish frying,) does this oil "smother" the rust.

Somebody smarter than me give me the low down on the lifestyles of rust to help me understand how this works.

 

[SatinSilver]

There's only one that I know of that's a living, breathing form:

http://en.wikipedia.org/wiki/Rusty_Wallace

 

[190E26FTW]

Originally Posted By: GreeCguy
Kind of a weird question, but here we go.

Early this year, I rebuilt my BBQ grill which I made from a 55 gal metal barrel. I burnt it out and then painted it with flat black BBQ grill paint. However, even with two coats, it started rusting in about a months time. Shortly after that, I had some used cooking oil from one of our fish fries and I poured that oil over my grill, (as well as coat the inside of the grill) and since then, there's not a spot of rust on it. It was just getting to the point of wearing/cooking off so today, I coated it with another coat of used cooking oil from another family fish fry.

It got me to thinking, does rust have to "breath" in order to "live." Other than creating a pleasing odor while cooking on my grill, (it smells like fish frying,) does this oil "smother" the rust.

Somebody smarter than me give me the low down on the lifestyles of rust to help me understand how this works.

needs oxygen to rust....no air no rust

 

[zzyzzx]

It needs oxygen to grow, but if left in the oil it doesn't die, it's just dormant.

 

[dparm]

Rust is formed when iron comes in contact with oxygen.

 

[JethroBodine]

Originally Posted By: dparm
Rust is formed when iron comes in contact with oxygen.


+1 no O2 no rust...all oxidation (fire) requires oxygen.

 

[NHGUY]

The theory behind POR15 is that it has no pores and starves the rust of 02 so it cannot get worse.Regular paints have "fissures" that make it pourus.Why does it have pores? The thinning and transfer agents need to gas off,they actually come from under the paint and bubble their way thru the top.Leaving the paint not totally waterproof.This is why cars in the junkyards have rust growing thru the paint in specks...it takes wax to seal paint,no wax (and no care at all) and you get rust thru the paint.

 

[NorWest5]

Rust never... sleeps.

 

[hemitom]

Originally Posted By: NorWest5
Rust never... sleeps.


Neil young.

 

[dave123]

Originally Posted By: NHGUY
The theory behind POR15 is that it has no pores and starves the rust of 02 so it cannot get worse.Regular paints have "fissures" that make it pourus.Why does it have pores? The thinning and transfer agents need to gas off,they actually come from under the paint and bubble their way thru the top.Leaving the paint not totally waterproof.This is why cars in the junkyards have rust growing thru the paint in specks...it takes wax to seal paint,no wax (and no care at all) and you get rust thru the paint.


Properly treated and painted steel will not rust no matter if it's waxed or not.

 

[Shannow]

Yep, rust needs oxygen to progress....so much so, that if you are about to enter a sealed rusty tank, the oxygen levels in the tank can be so low as to kill a person. It's part of our training in the power industry to recognise spaces that may be affected.

http://www.gmitoxics.com/jan06_killer_article.html

Paint reduces the rate at which oxygen can get at a surface, not quite eliminating it. Paint manufacturers do all sorts of trick to reduce the porosity. One example (not here) is installing mica or glass flakes. Rather than having to diffuse through 0.6mm of applied paint, it has to follow a maze through the laminated flakes, reducing the rate, and the contact with oxygen.

Your oil approach is essentially painting. Original paints (and linoleum) were slow drying, seed based (usually linseed), formed by the polymerisation of the oil forming a durable plastic. Fish oil spray is the same sort of "drying" oil.

If your cooking oil leaves a crust around the bottle top (the weep that's exposed to oxygen), then painting steel with it makes way more sense than frying with it.

 

[KrisZ]

That is why oil spray is so popular in Canada. It coats a lot better than tar or wax, it creeps into areas that might've been missed and it stays wet. So not only it repels water and salt, but also limits the oxygen exposure.

 

[GreeCguy]

What if I were to take cinders from the fire, grind them up and mix them with some used cooking oil to create a thin paste - would this work effectively as a "paint" for my BBQ? I've discovered that the simple oil method lasts about five months before it needs to be re-coated. The BBQ is never covered but sits on it's frame outside in all weathers, (and we've had a ton or rain this year in these parts). Wouldn't the cinder/oil combination work like the old lamp black of years ago? Or would it be more like an oily whitewash, (but in this case, a blackwash).

 

[GreeCguy]

Originally Posted By: KrisZ
That is why oil spray is so popular in Canada. It coats a lot better than tar or wax, it creeps into areas that might've been missed and it stays wet. So not only it repels water and salt, but also limits the oxygen exposure.


Can you spray oil through a pump up sprayer? (The kind you might use as a sprayer in your garden or use to spray for bugs around the house).

 

[Tegger]

Originally Posted By: GreeCguy
What if I were to take cinders from the fire, grind them up and mix them with some used cooking oil to create a thin paste - would this work effectively as a "paint" for my BBQ?

Not with vegetable oils, no. Vegetable oils generally contain oxygen as part of their molecular structure, so the use of vegetable oils means you'd actually be presenting the steel with fresh oxygen to use for corrosion.

Your method might work better short-term using motor oil, since that is a non-oxygenated hydrocarbon. But even motor oil will eventually wash away, oxygen once again intruding.

Remember Cosmoline, the original gun preservative? It's no longer made, but Brownell's sells a decent substitute with the ridiculous name "Rust Veto". You could paint that directly on the steel and it would be very effective, but it would melt and run with the heat. Plus it stinks, just like Cosmoline.

POR-15 might be your best answer. It's a brushable, paintable, epoxy-based coating that resists heat and moisture extremely well. It works by sealing the metal perfectly. Rust will continue until all trapped oxygen has bound with the iron molecules, after which corrosion stops dead and stays dead. Great stuff.