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View Full Version : How do I clean new steel for painting?



Shammy
11-29-2004, 11:22 AM
The brand new steel I bought for my table has some sort of oily substance all over it, probably to keep it from rusting too fast, and I need to know what to use to clean it off before painting it. I did a search but all I came up with was methods to remove rust. I don't have rust, just the film which turns my hands black after touching it. Is paint thinner or mineral spirits a good choice, or something that will just cut oil and grease like a degreaser? Appreciate your suggestions.

Shammy

Stimp
11-29-2004, 11:43 AM
I use Acetone

Zrexxer
11-29-2004, 11:50 AM
The brand new steel I bought for my table has some sort of oily substance all over it, probably to keep it from rusting too fast, and I need to know what to use to clean it off before painting it. I did a search but all I came up with was methods to remove rust. I don't have rust, just the film which turns my hands black after touching it. Is paint thinner or mineral spirits a good choice, or something that will just cut oil and grease like a degreaser? Appreciate your suggestions.Paint thinner and Mineral Spirits are usually one and the same, and will work although they're a little slow drying. I prefer to use acetone, which cuts oil quickly and dries clean without any oily residue. Some recommend lacquer thinner but it's no cheaper and I think acetone works better anyway. In any event, wearing chemical gloves and working in good ventilation or wearing a respirator is a good idea. Both solvents contain dimethyl ketones which can cause brain and central nervous system damage. If you're worried about these effects or have existing liver, kidney, or dermatological problems, you may want to just use the mineral spirits, which has a much lower toxicity and is safer to handle.

James D. Clark
11-29-2004, 11:57 AM
Suggested cleaners and methods by Stimp and Zrexxer all good. Make sure you don't have any open flames or do any welding until all the fumes are vented from the area. Clear the area of rags and towells too.

big rig guy
11-29-2004, 01:34 PM
Well your supposed to use whats called a silicone/grease remover, the methods mentioned with thinners etc will work, but what they do, is not lift the oil from the steel. The proper pre cleaner will lift oil and silicone from the material you want to paint. Generally what I do, is clean the majority of the oils with lacquer thinner and then wipe down with the precleanol. Leaving any residue on what you want to paint, can cause fisheyes and lifting of the paint later down the road.

This is available from your local autobody supply store and generally runs a little cheaper than lacquer thinners. I keep both in my shop, the pre cleanol, we use just before paint, as some urathanes are very fussy with oil/silicones. Sometimes have to wipe down multiple times prior to paint.

TJButler
11-29-2004, 04:03 PM
If the metal has a rust or mill scale I will typically use one of those Bear tex rapid strip wheels to get it down to bare metal first. A steel brush also can get much of the crud off.

I have generally used acetone with latex gloves to degrease but I am not real knowldgeable about it all.

I am real adamant about buying rust free steel when I purchase new. Many times they will try to sell me rusty metal as new. That really increases my workload in getting something finished.

TJB

49degreesnorth
11-29-2004, 04:45 PM
Let me just underscore that bit about being very careful with your acetone-soaked rags. I know from personal experience that an acetone rag becomes an instant fireball when hit by a grinder spark. :eek: Nothing damaged this time around but the rag; I got lucky. :rolleyes:

Chris

P.S. Simple Green works well and does NOT burst into flames. You will probably want to wire brush or sandblast to remove millscale, too, no matter what solvent you use.

enlpck
11-29-2004, 09:12 PM
P.S. Simple Green works well and does NOT burst into flames. You will probably want to wire brush or sandblast to remove millscale, too, no matter what solvent you use.

Be warned that ANY residue from simple green or any other detergent will cause problems with adhesion of the paint. A thourough rinse of four is needed, and any area's where it may get trapped need extra attention. It also won't get silicones off, and the alkali nature makes it unsuitable for some metals and alloys (aluminum, bronze, brasses among others) as it will remove alloy components near the surface. Mild steels arn't affected.

Side note: I am a converter believer. Makes for much better adhesion and helps protect the metal from rust if the finish gets dameged.

Shammy
11-30-2004, 10:45 AM
Side note: I am a converter believer. Makes for much better adhesion and helps protect the metal from rust if the finish gets dameged.

Not sure what you mean by "converter believer"?

enlpck
11-30-2004, 11:06 AM
Metal conversion coatings. Several types available, including phosphate types, which convert rust to iron phosphate, chromate types, and several others. The coatings don't flake, chip, are tough to scratch, and absolutely prevent rust. Also provide a better surface for paint to adhere to.

Shammy
11-30-2004, 03:23 PM
enlpck,

Now I know what you're talking about. I used to use Ospho and ChemPrime on rusty boat trailers and such. It turns iron oxide into iron phosphate. Will that work with this oily film I've described on my steel? I'm not sure what this stuff is, I just presumed it was some sort of coating put on at the mill to protect it from rusting too much before it was actually used for something. I hope it will because I have some on hand!

Shammy

enlpck
11-30-2004, 10:46 PM
enlpck,

Now I know what you're talking about. I used to use Ospho and ChemPrime on rusty boat trailers and such. It turns iron oxide into iron phosphate. Will that work with this oily film I've described on my steel? I'm not sure what this stuff is, I just presumed it was some sort of coating put on at the mill to protect it from rusting too much before it was actually used for something. I hope it will because I have some on hand!

Shammy

These won't remove oils in general. The oil isn't so much for protection as it is a remenant of the oil used in the rolling process. On hot roll products, it is cooked into the scale and burnt off to a great extent. Cold roll products usually have a healthy film.

Lots of good info already, but a few more points (worth every penny you are paying, and then some :) ):

detergents are dandy if you rinse well. Conversion coatings seem to be somewhat tolerant of detergent residue compared to straight painting.

Brake cleaner works well for flushing oil off small parts and in confined corners. Ventilation is real important. Read the can.

Acetone is quite good, but flamable as all heck.

Gasoline is useless as a paint prep, aside from the danger. It leaves residue.

Thinners do a good job.

Commercial paint prep cleaners are pricier, but can be stretched by using as a final clean (as Big Rig Guy said) after thinner.


I honestly don't worry too much for most things, like carts, shop racks-- Clean with whatever is most convienient (depends on the material condition-real oily, solvent first; light oil acetone; rusty oily old metal gets detergent and rinse first, as the water and detergent get into the rust well) hit with a conversion coat (I like phosphate converters for ease of use) and paint. I actually like older, slightly rusted metal for these jobs, because they take a converter well and take primer well. Most of what I do doesn't have to look perfect, fortunately.

Stuff where apperance really matters (vehicle finish, for example) gets left to our pro, primarily because he catches screw-ups before they happen. Cleaning is typically similar (detergent for heavy oil and dirt, rinse, rinse, general solvent, paint prep solvent)