Some common mistakes I've seen people make is not prepping bare metal properly for good primer adhesion. Keep in mind epoxy and DTM type primers need the metal to have some texture and it also needs to be perfectly clean. The perfect texture is achieved by sandblasting or sanding with 80 grit on a DA, some fiber discs like 3M's Clean-n-strip discs also work well. Failure to texture the metal and clean it well can lead to less than adequate adhesion. Blasting jambs and similar areas is usually no problem but outer sheetmetal should be left to a professional to avoid warpage-(Shine should do a thread on blasting techniques). Hand held gravity fed spot blasters are an economical way for anyone to clean small areas-they work well. When sanding change your paper often so it produces a sharp scratch pattern and not a shiny polished surface. Clean the bare metal with solvent based wax and grease remover then follow that with waterborne wax and grease remover-spray the cleaner on and wipe it off while it's wet, or you can pour the cleaner on one towel then wipe it on and wipe it off with a clean towel. Why two cleaners?-they each offer their own benefits. (Update: New SPI guidelines call for waterborne to be used first, then solvent base.) Should sandblasted metal be cleaned-definitely and especially if you recycled your sand. I've seen primer fall off of sandblasted steel when the person didn't clean it before priming. You'll end up with some towel fuzzies on a blasted surface as the texture grabs the fibers-no big deal just give it a light scuff with a red scotchbrite and a blast with the blow gun and they are gone and they need to be gone! Simple Green, 409, Dawn dish soap, Ajax, Fast Orange, Engine Degreaser????-- these can all be handy during the precleaning stages of a job but you shouldn't be cleaning your bare metal with them for the final clean before primer. Will a wire wheel work for texturing the metal-No they mostly provide a polished or burnished surface, they do work well for rust removal though. Will an acid etched surface provide enough adhesion? No, if you use acid make sure to neutralize it well and then mechanically texture the surface with sanding or blasting. Acid works great for rust removal but needs to be completely removed for any primer application. Safety concerns? you need to understand the safety concerns for all autobody products and tools-every one is dangerous in one way or another. Feel free to add or modify as needed.
FAQs
What do you clean bare metal with before priming? ›
Avoid using water to clean metal; instead, use a solvent such as acetone. It will dry quickly and leave a clean surface. If necessary, use a rust remover beforehand to clean surface rust.
Do you need to sand bare metal before primer? ›After the metal is clean, it needs sanding. Sanding helps create a rough surface. Painted metal which isn't sanded will be more prone to peel or flake off. If you're prepping metal that's already painted, you need to sand off and smooth.
Can you clean metal with vinegar before painting? ›The only nontoxic rust-removing chemical I'm aware of is white vinegar. It's an amazing rust remover for very light rust on metal. I saturate a paper towel with the vinegar and press it onto the rusty metal. Within a few hours the rust is almost always gone and I don't even have to rub the metal.
How do you clean body fillers before primer? ›When the panel has body filler, clean as stated on the unsanded portion of the panel. On the filler itself, use only the waterborne cleaner after blowing it off, and then blow any residual cleaner dry after wiping it off. The “why” is to remove any sanding dust left by the bodyman and allow for a better inspection.
How do you treat metal before primer? ›If the metal surface has been painted before, you'll need to remove old paint, rust, debris, grease, and dirt using sandpaper, a scuffing pad, or wire-brush tool. If the metal is smooth and has nothing on it, you'll still need to scuff up the surface of the metal by sanding so the primer can stick to the surface.
Can I use denatured alcohol to clean metal before painting? ›As a degreasing agent, it removes spots, grease, scuffs and surface soils from hard surfaces, including metal, tile, wood and plastic. It should be applied via a cloth or rag. We often use it to help clean surfaces prior to applying a coating or paint.
What is the best product to clean metal before painting? ›Instead of using water to clean metal, opt for acetone. This dries very quickly, so there will be no delays to your work. If you notice there is rust on the metal, use a rust remover to clear this first. After cleaning your metal with acetone on a clean rag, make sure you don't touch the surface again.
What grit sandpaper for bare metal before primer? ›Really, it does depend on what you are doing, and what the surface is like at the moment you start. If it's a fairly smooth surface, grades around 180–400 is probably what you want. For coarse work, 40, 60 or 80 may be a start. For a very smooth finish, 600 and up will be what you need.
Can I use brake cleaner to clean metal before painting? ›Common items used to clean surfaces before painting include solvent cleaners, brake cleaners, solvent wipes, alcohol wipes, and tack cloths. While all of these do a good job, they leave residue that can interfere with the adhesion and flow out of paints and coatings.
Can I paint after cleaning with vinegar? ›According to PROHousekeepers, when cleaning before painting, you only need warm water and a little dish soap for greasy kitchen walls. If you have stubborn spots that are not responding, you can use one of the cleaners they recommend, based on paint finish: Flat or matte paint: White vinegar or plain water.
How long can metal sit in white vinegar? ›
To tackle items with significant corrosion, submerge your rusty tools or knives in a bowl of white vinegar and let them sit overnight or as long as 24 hours. Once they have had a good soak, remove them from the vinegar and scrub the rust off with steel wool, a scouring pad, or a wire brush.
What do you clean primer with before paint? ›On filler and primer, use plain old Rubbing Alcohol. You can mix it 50/50 with water if you like, but I just use it straight. Use soft cotten rags like those you get in Rags in a Box which is just T-shirt material. Wipe it on with a rag in one hand, and wipe it off with a rag in the other hand.
What should I sand filler primer with? ›For best results, allow Filler Primer to dry for 1 hour before dry sanding. Test in an inconspicuous area to be sure Primer is dry enough for sanding. Block sand the area using 320-400 grit sandpaper.
Can you wash bondo before primer? ›I ussually try to avoid it if I can, bondo is like a sponge and absorbs water which isnt good for the bare metal underneath. The best way I have found to clean it is to blow it off with air gun and then wipe it down with prepsol to get any contaminants off before paint goes on.
How do you clean surfaces before priming? ›For surfaces that have exposure to oil or grime, like kitchen walls, wash with a solution of water and grease-cutting detergent and follow up with clean water to remove any residual cleaning agent. Finish by wiping the walls with a damp cloth.
What do you clean metal with before powder coating? ›The Best Ways To Clean Your Metal Surfaces For Powder Coating. First, determine what you'll be coating the most often. If you are coating sheet steel, for example, you will usually only need light oil cleaning. Angle iron or castings often need sand/shot blasting to remove scale and surface rust.
Can I use paint thinner to clean metal before painting? ›Hence the main points why NOT to clean the surface with automotive paint thinners are as following: 1. The main problem with acrylic (or any other type) of thinner used in a body shop, is that it dries too fast.