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The Spokesman-Review Newspaper
Spokane, Washington  Est. May 19, 1883

Ask the Builder: Painting rusty metal can be a lifesaving DIY job

The rust on this large natural gas line could eventually eat through the pipe and cause a catastrophic gas leak and explosion.  (Tribune Content Agency)
By Tim Carter Tribune Content Agency

Did you see in the recent news the catastrophic gas explosion that killed nine people on the island of Jersey in the English Channel? It’s early in the investigation, and the experts may not ever be able to pinpoint the cause, but I have my own idea based on something that happened to me two years ago.

I was hired by a small condominium association to do a thorough inspection of some outdoor covered decks that had leak issues and wood rot problems. This building was located just a mile or so from the Atlantic Ocean in New Hampshire. The flats in Jersey were subject to the same marine environment.

My inspection started at the uppermost deck, and I worked my way down to the ground-floor deck. When I was underneath the deck in a passageway that led to a basement door, I saw black iron gas lines that extended from the outdoor meters into the basement. These connected to the water heaters and furnaces.

The iron pipes weren’t black. They were a crusty brown, as they were completely coated in rust. I immediately informed the president of the condo association that these pipes must be painted with a special rust primer and then two coats of finish paint. I instructed her to make sure she read the instructions on the label of the special metal rust primer to prepare the pipes so the primer adhered well.

I was reminded of a quote from the captain of the Norwegian Dawn cruise ship. I had attended a talk of his five years ago while on a short cruise. He said, “The sea eats iron and men.”

If you remember some of your high school chemistry, you know this to be true. Saltwater is extremely corrosive to unprotected steel and iron.

I’ve been a master plumber since 1981. I’ve installed miles of black iron gas lines in my lifetime. I’ve hand-threaded each and every pipe with cutting dies. You may have never thought about threaded pipe, but where the grooves are, the pipe wall thickness has been cut away and reduced to create the threads.

This means the pipe is much weaker in these grooves. If rust has been working on the pipe eating away at the iron, and then the pipe is bumped or becomes stressed or bent by accident, the metal at the base of the grooves can crack as easily as you can pop the top of a soda can. Gas now starts flowing from the pipe like air from a blown-up balloon.

You don’t need to live near the ocean for this to happen. Normal rain or humidity in the air will cause rust to form and grow on unprotected iron or steel. Your house has all sorts of structural steel elements that are rusting. Many ignore this rust at their peril.

What about your deck joist hangers? I know they were galvanized when they were installed, but has that zinc coating worn off and do you see rust?

What about the nails that attach the deck joist hangers and other structural connectors to the wood? Is the copper in the treated lumber leaching out with each rain event, causing rust and corrosion?

What about those cheap electroplated roofing nails the roofer used to install your shingles? I’ve seen new roofing nails transform to rusty fasteners in as little as five to seven years. The best roofing nails are ones that are double-dipped hot galvanized. Period.

What about any steel support posts in your basement or crawlspace? Do you see rust on these? What happens if the rust eats through the post and someone bumps into it?

What about rust on any horizontal steel I-beams in your basement or crawlspace? Are you ignoring it?

If so, you’re making a sad mistake.

The good news for you is that painting rusty black iron pipe, as well as all the things I listed above, is absolutely a simple DIY job. Most of the high-quality rust primers and special rust finish paints are available in spray cans for those who don’t like to use a brush.

I recorded a video about five years ago showing the difference between two top rust-paint brands. The test panels in the ASTM scratch test were like night and day. I urge you to watch this video so you buy a paint that will last for many years, even in a marine environment.

The video can be found at this URL. Be sure you type in the word GO and the period that you see before