Q: What can you tell me about painting rusty metal? I want a fast and easy method to repaint an assortment of things in my garage and shed. Do you have to remove all the rust before you paint? Are there secret nontoxic chemicals that will remove rust? What paint would you use? Thanks. — Debbie M., Ely, Nev.
A: Nevada is dry. Debbie lives in the Great Basin, the place where rivers go to die. Even so, there’s enough humidity to rust bare metal.
I’ve had tremendous success over the years painting rusty metal. The good news is, you don’t have to remove all the rust. Not by a long shot.
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!
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Last weekend, I restored a wonderful two-wheeled hand truck that delivery people use. It was almost 50 years old and very well made. Cheap ones you see online or at home centers don’t come close to matching its strength or design. This is one reason I try to restore old things: I find that many of my older implements and tools are constructed much better than the ones I can buy today.
Years ago, the best metal primer I used had both zinc and chromate dust in the paint. Oh my gosh, was it a great rusty metal primer! I believe this paint was discontinued over litigation worries about heavy metals in consumer products.
I now use a name-brand rusty metal primer on rust-coated steel. So far, it has performed very well. I tested it just last year painting some rusty steel, and on purpose I didn’t coat the primer with finish paint. I subjected the primed steel to the harsh New England winter, including all sorts of salt spray from highway driving. Months later, the primer looked like the day I applied it.
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Step one is to read the label instructions on the can of the rusty metal primer you decide to use. Follow the instructions to the letter. The instructions often say to remove rust scale and as much loose rust as you can brush away with a wire brush or coarse 60-grit sandpaper. You can use a wire wheel on a spinning electric grinder to make this work go very fast. Wear leather gloves and full eye protection. A breathing mask is also a good idea, as some of the old paint you might be turning to dust could contain lead.
Share this articleShareOnce you’ve got the rust under control, take an old paint brush and use it to brush away any rust dust. Apply the primer and allow it to dry. As soon as the label on the primer says you can apply the finish paint, do it. This is often in just a few hours. Doing it this way allows the finish paint to get a much better bond to the primer than if you prime something and then paint it weeks later.
Purchase the most expensive gloss finish paint you can afford. Higher prices often (but not always) equate to better ingredients. Once again, follow the instructions on the label of the finish paint for professional results.
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Q: Tim, can you share advice about whether or not it’s a good idea to spray water on a hot outdoor AC compressor so it runs more efficiently? I saw an ad for a special sprinkler made for this purpose. It seems like it would work, as water refreshes me when I’m hot. — Jim McM., Boca Raton, Fla.
A: I absolutely love questions like this. I get them week in and week out on my AsktheBuilder.com website. Jim did the right thing, in my opinion, by reaching out to me to ask about something before spending money or doing something that might cost thousands of dollars to repair.
I prefer to apply critical thinking skills to questions like this. The first thing that pops into my mind would be the owner’s manual for the AC unit. I would want to read it to see if the manufacturer recommends for or against spraying the unit with water. I know, it rains on outdoor AC compressors, so how bad can it be to spray it with hose water?
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For one, the water from the hose might be hard, and limescale could start to build up on the cooling fins of the machine. Second, water from a sprinkler might not hit the compressor the same way rain does.
I would then think about whether I’m really saving money. In my case, I get my water from a well, so the water is free. I do have to pay a very small amount of money for electricity to get the water from the well, but maybe that’s a few pennies per day.
You may have to pay lots for water at your home. You would also have to time the water so it runs only when your compressor turns on. How much is this complex timer setup going to cost?
For all of this to make sense, you would have to save more on the electricity to run the AC compressor than you pay for the water plus the cost of the special sprinkler and timer setup. I’m willing to bet money that it would take decades, or longer, just to break even.
Subscribe to Tim’s free newsletter and listen to his new podcasts. Go to: https://www.AsktheBuilder.com.
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