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Cleaning Surfaces for Paint

So after wire brushing, sanding, wire wheeling or sandblasting old rusty metal for painting, what is the best solution for cleaning up the surface? So far I just airblast the thing to dust it off then splash the stuff with mineral turps and give it a good rag off, but I suspect this isn't removing most of the rust dust. It seems to help removing penetrating oil and stuff too, and flashes off in the sun fairly quick. Anyone got some pointers?
 

Andrew Mackey

Moderator
Re: Cleaning surfaces for paint

First, if blasted or sanded/wirebrushed, wipe down with a paiters tack cloth to remove most of the dust. Liberally flush with AAcetone. DO THIS OUTDOORS! Acetone is explosive in confined areas and can be set off with static electricity!:eek: Blow dry with compressed air and let set for a day or so so the volatile material can evaporate out of the pores in the iron. Make sure your air supply is dry or you will get rust spots on the clean iron! Mineral turps will actually soak into the iron - paint will peel off if painted over:eek:
 

cobbadog

Active member
Re: Cleaning surfaces for paint

Wax and grease remover is also another product similar to the tack cloths mentioned.
 

Mike in NC

Moderator
Re: Cleaning surfaces for paint

We use wax and grease remover, blow off with dry air, and lastly a tack cloth. Wax and grease remover is not similar to a tack cloth. A tack cloth will only remove dust, it will not remove wax, grease, oil, finger prints and so on. Brake cleaner is ok, but it will leave a residue, electrical contact cleaner is like brake cleaner but does not leave a residue.
 

Motorhead

Subscriber
Re: Cleaning surfaces for paint

If it is steel, I have used for years phosphoric acid or Zep shower tub and tile cleaner. It is hydrochloric acid based so use in well ventilated area. I scrub the bare metal down with the acid and a scotchbrite. it cleans all residue off and etches the metal. I rinse it clean with hot water and dry quickly.
 

PaintChemist

New member
Re: Cleaning surfaces for paint

Motorhead's method for cleaning is a good one but let me add some things. Hydrochloric Acid (sometimes called Muriatic Acid) is used by many industries to etch iron, steel and concrete. The hot-dipped galvanizing process starts by "pickling" steel in the acid to remove rust. Be aware however that this acid is real nasty stuff. Always wear eye protection and gloves when handling it. Make sure your work area is well ventilated or work outdoors if possible. Also, be aware that Hydrochloric Acid is VERY reactive when mixed with other chemicals and any inadvertent reaction can kill you. Don't underestimate my warnings. The acid will remove rust very quickly and can easily dissolve your part if you are not careful. I suggest you Google a safety data sheet for Hydrochloric Acid and read what it has to say. Happy rust busting!
 

mihit

New member
Re: Cleaning surfaces for paint

Wait until the wife is out and heat the parts in the oven. 50-200° celcius depending how quick you'll handle em and how thick.
Agree turps will leave oily residue.
Acetone, methylated spirits, moonshine, isopropyl will all degrease and evaporate quickly (VERY quickly, if the parts are warm) and will not etch.

As said, acids WILL etch. a 2-3% solution of HCL would be more than enough. Citric acid and acetic acid (vinegar) also work, are less toxic, easier disposed of, smell better. The downside is that it will take longer to etch, again this process is speeded by being warm.

When I paint I want my parts warm to the touch but not too hot to handle. Mist coat, then proper coat. This sets the paint smartly, if you don't have a paint-baking oven.
Thicker parts, cast iron etc will hold their heat for a long time, which acts a bit like an inside-out oven.
 
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Scotty 2

Active member
Re: Cleaning surfaces for paint

Hello all
Don't a lot of gloss paints (if not all)need time to 'flatten out' and 'wet' the item to achieve their high gloss and durability? Would a warm to touch, but not too hot to handle, surface allow this?
I don't think I'd want a heated surface to put paint onto.

Cheers Scott
 

mihit

New member
Re: Cleaning surfaces for paint

Don't a lot of gloss paints (if not all)need time to 'flatten out' and 'wet' the item to achieve their high gloss and durability? Would a warm to touch, but not too hot to handle, surface allow this?
I don't think I'd want a heated surface to put paint onto.
https://globalfinishing.com/2012/04/20/paint-booth-temperature-settings-a-practical-guide/
http://www.spraytechblog.com/product-knowledge/paint-curing-oven-drying-time-can-decreases-by-35-percent/
https://www.hotrodders.com/forum/baking-paint-106860.html
http://autobodystore.com/forum/showthread.php?5628-Why-do-body-shops-bake-cars-after-painting

Knock yourself out champ.
 

Scotty 2

Active member
Re: Cleaning surfaces for paint

My name is Scott...not champ.
Those websites all state drying temperatures can be elevated (up to a point) with the first site saying application of the paint is around 70 and up to 85 degrees F, which is about 21-29 degrees Centrigrade.
There is a difference between application temperatures and drying temperatures. Huge difference.

I quote from the first reference site: Since much of the country is warmer than 70 degrees for at least some of the year, paint companies have different catalyst and reducers to compensate for the rapid increase in cure times while applying the coating.

Using the rule of 15, it is easier to address why temperature control is so important. If you are spraying a product that takes 30 minutes at 70 degrees to flash before it can be coated with the next step, a shop could effectively cut that time in half (to about 15 minutes) if they have the ability to raise the temperature in the booth to 85 degrees

Remember that that website is American. They measure temperature in Fahrenheit.
 

mihit

New member
Re: Cleaning surfaces for paint

My name is Scott...not champ.
Those websites all state drying temperatures can be elevated (up to a point) with the first site saying application of the paint is around 70 and up to 85 degrees F, which is about 21-29 degrees Centrigrade.
There is a difference between application temperatures and drying temperatures. Huge difference.

I quote from the first reference site: Since much of the country is warmer than 70 degrees for at least some of the year, paint companies have different catalyst and reducers to compensate for the rapid increase in cure times while applying the coating.

Using the rule of 15, it is easier to address why temperature control is so important. If you are spraying a product that takes 30 minutes at 70 degrees to flash before it can be coated with the next step, a shop could effectively cut that time in half (to about 15 minutes) if they have the ability to raise the temperature in the booth to 85 degrees

Remember that that website is American. They measure temperature in Fahrenheit.
Yes. Scott Boofhead, if your Youtube is to be believed. Do you mind if I call you Mr. Boofhead? I just don't feel like we're friendly enough for a first-name basis yet champ. :O

Not sure about you, but when I put paint on things, I want it to dry. The fact that as soon as you open the tin/pack/add the hardener/start spraying the paint is "drying" seems to have eluded you.
Those were the pretty much the first four things that came up when I searched for "baking paint on parts".
By all means, have a search and come back with your well-researched opinion. I'm always interested in learning a better way to do things.

I've stated how I do it. You (baselessly, I feel) contradicted it.
Please feel free to jump in with your painting methodology.
 

cobbadog

Active member
I have used a commercial product that says it has hyperchloric acid in it and is sprayed directly oto the steel. This must be a diluted version of hydrochloric acid which I have also used inside a rusty fuel tank to clean it up.
I am about to spray my tractor but have damp weather here at the moment so I will wait for that to pass. But before spraying
i will also wait for the chill to go off the air air as I feel that cold steel tends to flatten the gloss at times.
I can't see any benefit in cooking up the parts before spraying as it may tend to have an adverse reaction in the way the paint is intended to dry. Years ago there was a process known as baked enamels applied to cook ware and cups and could be chipped if dropped but that was a totally different type of paint and would be like comparing water base paints to 2pac.
 
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