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Old 11-12-2009, 05:31 PM   #1
h3llfir3
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Question about rust protection

I want to coat a piece of metal with paint so it doesnt rust. It is a random piece of metal i found in my house and it is going to be used to secure a piece inside my headlight. The area that the piece of metal will be touching gets very hot (too hot to touch without burning off your skin). If i use a rust paint on the piece of metal, will the rust paint burn up and cause fumes or not?

Does any paint work as rust protection or does it have to be a rust paint? If i used a high heat primer on the piece of metal, would this also stop rust?
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Old 11-12-2009, 07:02 PM   #2
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Smile Re: Question about rust protection

the high heat paint or primer would stop the rust. the idea is to seal the metal from the elements. no moisture and air, no rust.
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Old 11-12-2009, 07:06 PM   #3
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Re: Question about rust protection

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the high heat paint or primer would stop the rust. the idea is to seal the metal from the elements. no moisture and air, no rust.
-oh okay, i think i understand. but why do they make rust paint if any paint stops rust?

-and is it okay to use high heat primer by itself and this will stop the rust?

-what happens to rust paint when it gets very hot? (too hot to touch without burning your finger). Will it burn up and cause fumes?
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Old 11-12-2009, 07:10 PM   #4
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Re: Question about rust protection

high heat primer should be ok. the rust paint, if gets too hot can start to peel and crack exposing the metal to the elements. with the primer, use more than one coat to make sure the metal is sealed.
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Old 11-12-2009, 07:15 PM   #5
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Re: Question about rust protection

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high heat primer should be ok. the rust paint, if gets too hot can start to peel and crack exposing the metal to the elements. with the primer, use more than one coat to make sure the metal is sealed.
-ah ic, interesting. so with primer you have to use more than one coat and with rust paint you dont?

-also, i can use primer alone for rust protection. correct?

-one more thing. can the rust paint burn up and give off fumes if it gets too hot?
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Old 11-12-2009, 07:25 PM   #6
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Re: Question about rust protection

the rust paint is not made for high heat. dont know about the fumes. the primer preps the surface for paint, thats why it would be best to go with more than one coat. but that alone should work.
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Old 11-12-2009, 07:39 PM   #7
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Re: Question about rust protection

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the rust paint is not made for high heat. dont know about the fumes. the primer preps the surface for paint, thats why it would be best to go with more than one coat. but that alone should work.
oh okay thanks for the great info. so i can use primer alone and no rust will occur? and i have to use more than one coat of primer because that will act like a primer and a paint right? if i just use one coat of primer what will happen?
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Old 11-13-2009, 02:33 PM   #8
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Re: Question about rust protection

You want to use a high-heat primer so that it can withstand the repeated thermal expansion as the light heats it up. Normal paints will crack and peel off because they become brittle when repeatedly heated.

Just primer should be fine if the piece won't get much water slashed on it. Apply in multiple, thin coats rather than one thick coat to ensure that all the solvent has evaporated between coats. Trapped solvent in a thick coat causes bubbles, craters (especially when heated), and generally lowers adhesion because the paint underneath the surface isn't "cured".

When prepping the metal, sand away any rust and round off any edges. Wipe clean with clean dry cloth and degrease with brake cleaner. If you can hang it on a hole, it makes painting and drying easier and faster.

Finally, make sure the air temperature is warm enough...check the can label for minimum temperature, usually at least 50°F but some are up to 70°F. When I have to paint on a cold day, I position an infrared space heater to warm it after each coat. An infrared thermometer will help you get the right surface temp by getting the right distance from the heater...they're cheap and very handy.

Hope this helps!
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Old 11-14-2009, 01:35 PM   #9
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Re: Question about rust protection

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Originally Posted by jdmccright View Post
You want to use a high-heat primer so that it can withstand the repeated thermal expansion as the light heats it up. Normal paints will crack and peel off because they become brittle when repeatedly heated.

Just primer should be fine if the piece won't get much water slashed on it. Apply in multiple, thin coats rather than one thick coat to ensure that all the solvent has evaporated between coats. Trapped solvent in a thick coat causes bubbles, craters (especially when heated), and generally lowers adhesion because the paint underneath the surface isn't "cured".

When prepping the metal, sand away any rust and round off any edges. Wipe clean with clean dry cloth and degrease with brake cleaner. If you can hang it on a hole, it makes painting and drying easier and faster.

Finally, make sure the air temperature is warm enough...check the can label for minimum temperature, usually at least 50°F but some are up to 70°F. When I have to paint on a cold day, I position an infrared space heater to warm it after each coat. An infrared thermometer will help you get the right surface temp by getting the right distance from the heater...they're cheap and very handy.

Hope this helps!
hoooo weeee hahaha thats a lot of help ! thanks

hey, why did you say "as long as the piece wont get much water slashed on it".

------------------------------

the guy above also said something about me having to use more than one coat of primer because primer preps the surface for paint. can you explain a bit on this topic?
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Old 11-14-2009, 02:28 PM   #10
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Re: Question about rust protection

I meant to type "splashed"...oops. If it only occasionally gets wet, then the primer should be sufficient. But for more continuous wetness, you'd be better adding a topcoat to help repel the water. For stuff that needs to be protected but not right in plain eyesight (blacked out), I like to use ColorPlace RustControl Spray Enamel. Great stuff for primed brake drums and warranted to stop rust for 2 years.

Primer is kind of the go-between the metal and the color coat and does two things. It provides most of the corrosion protection because of its higher solids content and provides a matte surface finish for the color coat to physically adhere to. The primer and color coats are also sometimes formulated to bond chemically (you spray the color coat on after a certain period of cure time). But canned spray paints usually don't do this since primer/colors are not always used together or the same brands.

You want to use more than one coat to ensure that the bare metal is completely covered by the primer. Any tiny bare spots will be a weak spot for water to penetrate the color coat (if used), reach the bare metal, and start to form rust.
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Last edited by jdmccright; 11-14-2009 at 02:41 PM. Reason: added info
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Old 11-14-2009, 02:34 PM   #11
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Re: Question about rust protection

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Originally Posted by jdmccright View Post
I meant to type "splashed"...oops.

Primer is kind of the go-between the metal and the color coat and does two things. It provides most of the corrosion protection because of its higher solids content and provides a matte surface finish for the color coat to physically adhere to. The primer and color coats are also sometimes formulated to bond chemically (you spray the color coat on after a certain period of cure time). But canned spray paints usually don't do this since primer/colors are not always used together or the same brands.
oh, okay. but he said it is best to go with more than one coat of primer. why is that?

and since rust paint isnt for high heat, can it burn up and cause fumes when heated?
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Old 11-14-2009, 02:51 PM   #12
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Re: Question about rust protection

The difference between regular and "high-heat" paints are mainly the solids used for covering the part. Normal paints may use pigments (the color) and binders (the stuff that holds the color particles together and forms the barrier) that can break down when heated. High heat paints use special pigments and binders (usually mineral- or ceramic-based) that don't break down under high heat.
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Old 11-14-2009, 03:21 PM   #13
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Re: Question about rust protection

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Originally Posted by jdmccright View Post
The difference between regular and "high-heat" paints are mainly the solids used for covering the part. Normal paints may use pigments (the color) and binders (the stuff that holds the color particles together and forms the barrier) that can break down when heated. High heat paints use special pigments and binders (usually mineral- or ceramic-based) that don't break down under high heat.
but do the non high heat paints such as rust paint burn up when exposed to high heat and then give off fumes?
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Old 11-14-2009, 05:27 PM   #14
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Re: Question about rust protection

Paint formulations will vary, but there is the possibility of discoloration, smoke, and maybe fire. The pigments and binders have organic components...basically plastics...that can oxidize rapidly when heated. That's why you see a temperature limit, usually ~200°F, listed on the directions for use. Above that, plastics and similar organics start to break down, oxidize, or melt.

If you can't find a high temperature primer, you can use a paint for exhaust headers but not brake calipers. Exhaust paints are made for long sustained high temperatures whereas calipers are only intermittently hot.
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