How to Get Aged Look on Galvanized Roof

A. I have seen a slurry of fine pumice ⇦this on eBay or Amazon [affil links] used with tampico brushes, to mechanically polish down the shine of zinc and other hot dip coatings (during the sheeting manufacture, not after installation). Using a very fine - grade FFF pumice, should result in a pewter-like finish. It is not expected that the slurry will pick up any appreciable zinc off the sheet surface, but thinking environmentally, it might be best to arrange to rinse the slurry off the roof and collect it for proper disposal.

Your call, and this will take a lot of labor, I'm sure. Someone working with such roofing may give you an estimate of how long nature will take to give about the same finish. My estimate would be a year, or less.

Good Luck.

A. I have done a few Mexican restaurants that have this look, the electrical conduit was washed with sulfuric acid/water solution and I think the tin roofing was washed with the same. I have heard that Hydrofluoric Acid may be used but be very careful with this extremely dangerous acid. It will eat glass.... I would suggest testing of several solutions before trying on your project.

Good luck.

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Ed. note: Thanks Craig, but hydrofluoric acid has no role in this at all and is the most dangerous material you can imagine. Please see the entry of December 1, 2010 and don't even consider hydrofluoric acid.

A. Have used vinegar ⇦in bulk on eBay or Amazon [affil links] , bleach, strong salt solution, the main thing is you need "acid". I have never used any acid that would be harmful should my grandkids be around while I have worked on tin in the past. Set the tin on your drive way, pour on a vinegar & salt & let it set.... no scrubbing. Just be careful where you wash the salt off to, it will kill your plants.

A. There's a multi-step painting process by modern masters called metal effects that can be used on exterior metal roofing. I think it's a little pricey if I remember correctly, but it looks really nice. There are a few different finishes available....aged iron, copper patina, etc. hope this helps

It's a 4 step process....a coat of seal over the steel, then a coat of metallized paint that matches the steel over that, then a coat of rust activator (which supposed oxidizes in minutes) and then another coat of seal over that....you can read more about it at the modern masters website under metallic effects. There's also an image gallery with some examples of rust effects used on exteriors.

A. I have primed galvanized surfaces with vinegar before painting and I have completely removed galvanization with Muriatic acid. Any acid-weak or strong will work at removing the galvanization from sheet metal. The acid from years of rain will remove it, but stronger store bought acids will cause it to rust faster. Rust is nothing more than a burning action taken on the metal by oxidation just as ashes from a fire. The zinc coating just protects iron from oxidation. Remove the zinc with acid.

I've seen movie sets in New Mexico sprayed with varying degrees of diluted Sulfuric acid just a few weeks after construction that looked a hundred years old in a very short while.

A. Try phosphoric acid. It'll knock the glint off of galvanized surfaces and leave them quite dull. Repeatedly soak the panels and rinse with plain water. Phosphoric is a common fertilizer element so it's not dangerous to the ground in the concentrations you'll use. In fact, your grass may grow greener if its soil PH is too high!

You'll need to wear rubber glovesrubber gloves ⇦this on eBay or Amazon [affil links] and protective gear, but it won't hurt you if you get splashed (unless it's the eyes, nose, ears, and so on). I generally apply it with a red scotchbrite ⇦this on eBay or Amazon [affil links] abrasive pad. Remember to rinse the panels when you're done.

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Ed. note: Don't ever use acids or strong alkalis without wearing goggles ⇦this on eBay or Amazon [affil links] .

A. Try using diet Coke, the acid in it will dull even polished aluminum, and it will be environmentally friendly.

Thanks, Father Jameson, but don't use a torch on galvanized material. Welders who weld galvanized metal and inhale the zinc fumes get flu-like symptoms called "metal fume fever" -- which you can read more about by searching our site for that term.

Regards,

A. Hi, Billy. I assume we're actually talking about zinc coated steel sheet metal rather than tinplate or solid tin. But once the zinc is gone, rust will occur as soon as the same day or next day.

Vinegar plus salt, or diluted household bleach ⇦ bleach/sodium hypochlorite in bulk on eBay or Amazon [affil links] are probably a bit safer than sulfuric acid or muriatic acid. Good luck.

Regards,

A. Mac,
I'd be a bit cautious about believing your contractor there, I'd be more concerned that the zinc isn't uniformly applied than getting it to look uniform.

Outside that, mild vinegar solution (1 gal vinegar, 9 gal water) should help speed it along. I'd advise against it though, if it ain't broke, don't fix it.

A. Hello Inice,
When the roof was nailed or screwed to the rafters where there rubber grommets used to seal around the holes? If they were used, were the screws or nails over torqued so the grommets are not seated properly? Im not trying to be smart but I would address the leaks first so you don't have to keep cleaning furniture and the deck. It could very well be that a portion of the salt / bleach application was occluded in the treated galvanized steel, and was liberated after the roof heated up by the sun. I would assume that the drips appear after a rain. As far as the stains on the cedar deck, you may have to sand. I'm not a wood expert and don't know how porous treated cedar is.

Q. Yes, thanks. Grommets were used and properly placed and the moisture isn't from the top, but the bottom of the steel. This process has been used before with great success but we read that besides Muriatic Acid, the salt/bleach solution would speed things up. This was a BIG mistake. The muriatic acid had worked beautifully in the past - ALONE. We also agree that the salt/bleach part is the problem. I'm going to clean the rafters with Oxalic Acid and then the deck since my search for a remedy suggested this (I hope!). I'm keeping my fingers crossed this works, and next time stick with Muriatic Acid alone for roofing material!

Hello again Inice,
I don't have experience with the use of oxalic acid on cedar, and I hope this works for you. It seems odd that the moisture and drips are originating from the underside of the steel, especially if you are certain there are no leaks coming from the top of the roof. I would be interested to know how soon the roof panels were installed after the bleach/salt solution and water rinse process were completed.

That's a good observation that was bugging me but didn't make it to my conscious mind. Is it possible that the topside of the panels was well rinsed, but the bottom wasn't, so the condensation is causing drips of chemicals? Ever notice how slimy bleach is? It's very difficult to rinse.

Regards,

We're curious if the rinse needed to be more like a pressure washer [affil links]! It was left on the driveway 2 days actually, then sprayed with a hose. The next day it was put on. We're in high desert, no moisture really. Condensation was from early morning moisture only, no rain. I'll be doing the experiment with the oxalic acid this weekend. The dreaded droplets seem to have stopped. I'm thinking I might take a strong hose and spray the underside of the roof before trying the oxalic acid just to make sure most of it is off. I'm still thinking the salt/bleach should be eliminated if doing this for roofing material. Curious if this happens often when adding this step. Bad decision on our part. Hindsight 20/20 of course

Hello Inice,
Thank you for sharing your success. By doing this you have enlightened many readers and responders. We all learn something new every day!

A. Try to put a coat of decking oil on the aluminium sheets. Gives an aged look and protects the aluminium sheets, works really well. I would never use acid as it reduces the life span of the roof.

A. Instead of an acid, you should use sodium hydroxide. Some of the commercial oven cleaners ⇦this on eBay or Amazon [affil links] (e.g. "dirtoff") have concentrated sodium hydroxide as an active ingredient. Spray sparingly from 40 cm distance and you get a great aged effect.

A. Hi Ronda. If muriatic acid did nothing, when we all know that zinc reacts instantly with it, I'd start to suspect that the panels are painted rather than galvanized. There are a lot of faux finishes on roofing sheet these days. I once visited a plant that roll-coated the roofing sheeting with paint in every faux finish you can imagine.

Regards,

A. Hi Judy. Does a magnet stick to it? If it doesn't, it's solid aluminum. If it does, it's aluminized steel (assuming you are right that it's not galvanized).

If it's solid aluminum, spraying it with oven cleaner (caustic solution) should dull it. Note that this is dangerous and environmentally questionable. You must wear at least goggles ⇦this on eBay or Amazon [affil links] and rubber gloves ⇦this on eBay or Amazon [affil links] , while making sure no children or animals are around. Then you must rinse into a trough to capture the caustic and neutralize it with vinegar (most people think that consumers and homeowners should not mess with strong chemicals this way, and they'll foam a lot more than you expect).

If it's aluminized steel, I'd be concerned about losing most or all of your rust protection. Good luck.

Regards,

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A. Haven't tried this on galvanized yet, but I know that Urea is used to add age and patina to raw copper. While it used to be hard to find, it is now readily available as "Ad Blue" ... the liquid used in today's diesel car and truck engines to turn the NOX into N and O. You can buy it in any auto parts store.

A. Re: White spots from galvanized roofing. Zinc has different levels of oxidation. When left to sit in contact with an anodic material it will form a white chalky oxide and when heated above roughly 1400 °F it will form the toxic zinc oxide mentioned in this thread, which is yellow in color. The prior may have been your problem and the acid may have washed away an anodic material.

In regards to acids. Remember, all acids are compounds with available H+ ions. H+ ions bond to metals and oxidize them. The best acid, assuming equal mol, to dissolve any metal will [almost always] be an acid made of an element that forms the most soluble compound in water after the acid has oxidized the metal.

Strength is another factor, vinegar has a low mol (amount of acid available in solution, essentially) and is also a weak acid (less H+ per mol) sulfuric, nitric, phosphoric (the acid in Coke), hydrochloric are strong acids (H++). Diluted, these strong acids can be used just as safely, obviously because most of you have drank a soda in your life. Always add acid to water. A drop of water may boil if added to concentrated acid.

As for aging: I like a 7" angle grinder ⇦this on eBay or Amazon [affil links] with a 50 grit disk. Works great. Drink extra coffee and add 3 eggs to your breakfast. I think salt makes the most natural finish. Plenty of time for more coffee while it works.

A. I have found that "EASY OFF" over cleaner in the yellow can works great to remove the zinc coating and accelerate the aging process. The active ingredient is sodium hydroxide. Spray it on thick leave it for three hours then wash it of with clean water. You will need to rinse and wipe several times to get all the white residue off.