Great article and very really well written. I'm repainting an old steel
bird cage with a tiny bit of rust and some of the powder coating has come
off.
It's been maddening getting info from the HD store where I've been buying
paint. They almost had me talked into priming with latex or water based
primers. Or I got a lot of "I don't know's," isn't their job "to know."
I'm glad I read labels and picked the oil based primer 1st (Zinsser). I am
done sanding, am ready to paint. One tidbit of info I came across on a lot
of bird forums is that Zinc based paints or finishes can be poisonous for
birds and possibly children if they gnaw on the object. It wasn't easy
finding something WITHOUT a rust inhibitor (usually zinc, or sometimes it
says rust inhibitor, but you're really not sure what is doing the
inhibiting & I'm not taking chances).
Anyway, so if anyone is in my boat - doing a project for a steel object
that will be in contact with a curious critter - human or animal- look for
the words "safe for children's items"...it will mean there is no rust
inhibitor in your product, but it will be safer in the long run. I plan to
paint with a super high gloss latex based paint used for high
traffic/handling and chipping. The bird I have doesn't chew much, but this
should be fine for him - he weighs about 2 ounces, hardly a destoyer.
I've used a super high gloss cabinet/high use paint before on a metal desk
from the 50's. I'm sure everyone would groan at this thought (using latex),
but no kidding I could scratch my nails on it and bump it and it was tough
as nails. Only bad thing with this formulation - it's rather gooey to
apply, not as creamy as normal latex's for walls etc..
Ok, a mouthful there. thanks for your article.
Paint and Primer as Rust Inhibitor
Summary: The right paint and primer can deter rust.
Avoid the job of rust removal by using primer and paints with rust inhibitor.
Rust preventive primer contains rust inhibitors - check the labels. Oil based
paint makes the best primer to serve as a rust corrosion inhibitor.
Related Articles: Painting Tips, Primer, Prevention
Rust Inhibitive Paints and Primers
Corrosion is a killer. It does it to steel, aluminum, zinc, magnesium, lead, and tin in cold blood. Often there are two accessories to the crime - contaminated water and air. You have witnessed this process no doubt. A shiny penny becomes dull brown and eventually green. Bright aluminum turns dull. Fresh, bare steel can be coated with a fine haze of rust in a matter of hours. I know, I've seen it happen in front of my own eyes.
States of Energy
When you look at any metal product, did you ever think that the metal is unstable? Probably not. I didn't think about it until I wrote this column. When metals like steel, copper, aluminum, etc. are refined, they are taken from a stable state (ores in the ground or rock) into an unnatural state. Think. You just don't dig into the ground and pull out I-beams......
Thus, once the metal is refined, it tries to go back to its original stable state. Different metals go back quicker than others. The ones that require the most energy to refine, go back faster to their natural states. In other words they corrode more readily.
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- Copper
- Nickel
- 410 Stainless Steel
- Titanium
- 304 Stainless Steel
- Silver
- Gold
- Platinum
The Corrosion Process
Steel rusts or corrodes because the steel is actually being eaten alive. The steel rusts, flakes off and disappears. Water which contains impurities (most water does, including rain water!), contacts the steel and creates a battery much like the one in your car.
The water contains ions which create a small electric current. The electric current pulls the iron atoms right from the steel. Furthermore, the steel reacts with air and oxidizes. This is the rust you see. Corrosion can be stopped. Simply do not allow the steel or other metal to come into contact with water and air. This is not as hard as it seems. Think of your car. Many of the body parts are steel which doesn't readily rust if left protected.
The Key is in Chemistry
Paint manufacturers all have chemists who work for them. They know that you can inhibit corrosion by controlling the chemistry at the surface of the metal. In other words, you can treat the steel with a coating which chemically alters the surface of the steel to make it less likely to give up the iron atoms. Rust inhibitive pigments in paint do this.
Some excellent rust inhibitive pigments are metals which are active. Zinc, chromate, lead, barium metaborate, etc. all make great chemical coatings which can protect steel. However, we all know lead is very poisonous. As such, it is tough to get paints that contain lead. Navy ships for years had paints which contained vast quantities of lead. It really protected the steel hulls from rust.
Check the Label on the Can!
Priming steel can't be done with just any paint. Look at the label and make sure you have a primer that contains rust inhibitive pigments. If the paint has them, it WILL say so on the label. If it doesn't, keep looking!
Be sure the primer you use is oil based. Oil based paints can simply coat the steel better. They flow better into the microscopic surfaces of the steel. This provides much better holding power. Not only that, oil paints are great vapor barriers. Water vapor and air itself simply can't pass through. This is vitally important if you want to stop the corrosion process. Good luck on your painting project!
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