Q&A / 

Restoring Rusty Paraphernalia and Water on AC Units

This 50-year-old two-wheeled hand truck was neglected and left outdoors for quite a few years. With less than two hours work, it looked brand new. (C) Copyright 2019 Tim Carter

Restoring Rusty Paraphernalia

QUESTION #1: 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 non-toxic chemicals that will remove rust? What paint would you use? Thanks. Debbie M., Ely, NV

Nevada is dry. Debbie lives in the Great Basin, the place were rivers go to die. Even still, 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 non-toxic 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!

Just this past weekend I restored a wonderful two-wheeled hand truck that you see delivery people use. It was almost fifty-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 as I find that many of my older implements and tools are constructed much better than what I can buy today.

hand truck finished

Years ago the best metal primer I used had both zinc and chomate 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’s 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.

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. Often the instructions 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.

Once 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. Often this is just in 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.

Water on AC Units

QUESTION #2: 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, FL

I absolutely love questions like Jim’s. 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 owners 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?

For one, the water from the hose might be hard and lime scale 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’d 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 electric 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’d also have to time the water so it only runs each time your compressor turns on. How much is this complex timer setup going to cost?

For all of this to make sense, you’d have to save more on the electric 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, to just break even.

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