Using Ospho

[jiminbartow]

This is Model T related because Ospho can be used to neutralize rust on a Model T body. Ospho is a phosphoric acid based solution that converts rust to a black inert substance that ceases to deteriorate metal. Some equate the neutralized rust to a protective primer. I have not used Ospho (www.Ospho.com) in a very long time and need to use it to neutralize sections of rust on a metal shingled roof prior to coating it with a rubberized coating. If there is a section of rust surrounded by good metal, and you spray the Ospho on the rust, will the Ospho only treat the rust and not affect the good metal? In other words, after treating the rust and prior to painting, I plan on washing and scrubbing the entire roof with TSP with a long handled brush to remove the old oxidized coating. When washing the roof, will the Ospho wash off of the unrusted metal? The reason I ask is because if the Ospho will not wash off of the unrusted portions, I don’t know how the rubberized coating will adhere to the dried on Ospho. Thanks for your help. Jim Patrick

[Scott_Conger]

Jim

it looks like select shingles have lost their zinc coating allowing rust. For certain the Ospho will aggressively go after the good zinc coating. I use it to turn shiny new bolts/nuts into bare steel by soaking them in a jar of Ospho for about 5 minutes.

Since the rust is quite localized, I'd be inclined to spritz it onto the rusty shingle and then scrub with a scotchbrite pad to keep Ospho contamination off of the good shingles as much as I could. Paper towels blotting the area and then letting it dry should be fine. In high humidity areas such as yours, it will be VERY slow to dry if left on in any quantity and then become sticky where drips congregated. If toweled down to a film, it dries nicely, though you will see whitish powder where it accumulates in crevasses. A clean stiff brush will remove the excess and then primer/paint will stick really well...I do not know about your rubberized coating, though and suggest you test all of this on the ground, on something that is similarly rusted.

When I was in FL, I used gallons of Ospho on various projects and followed their directions and never had a disappointment much less a failure. In the past, I've seen folks on the Forum give advice that was seriously contrary to the products instructions and I never felt the need to have the product fail, when the instructions produce such good results.

Here in WY I have bought the stuff by the gallon both on-line, and at Ace Hardware (hardware stores are still hardware stores here). If you can wait a week for delivery, on-line can be much cheaper.

good luck and be very careful...you have a lovely home BTW.

[TXGOAT2]

One very good way to conserve forest products is to build a structure TO LAST.

[jiminbartow]

Thank you Scott. Very helpful. Is it best to brush it on with a paint brush or spray it on? If spraying, what type of sprayer do you recommend that won’t stop up or be attacked by the acid in the Ospho? I have not used Ospho since 1985 and seem to recall that, at first, it went on well with a brush, but as I brushed it on, the brush and surface I was applying it to started to get sticky. After 35 years, or so, is that still the case? Jim Patrick

[George House]

Jim,... I’m in agreement with everything Scott said but have no idea what Pat meant. I’ve used Ospho a lot specifically on Model T parts over the years. I ve always brushed it on. It’s not a good idea but it can get on your hands and not hurt you but dripping on cement it will eat into the cement. Only when I used it on sheet metal did I feel the need to neutralize it with baking soda and water. I’d advice you to brush it on rusty shingles and wash it off after a few minutes. I hope this helps.

[George Mills]

I went to Florida on the Gulf Cost and only then found Ospho. I'd defer to Scott who lived long on the Suncoast before heading to Y-oh-ming for 'retirement'.

I have used it to 'restore'/'age' Model T tools and am happy with the results. I was going to have a big patio set redone in powder coat and then hung up on 'cleanliness' that on went Ospho on everything...and that's where the stickies come from if you let it dry...places it had no use. Ammonia wiped that off over the stuck paint and then rather than powder coat I went with a Jim from Bartow approach and finish rattle canned with Rustoleum Appliance Enamel. House there is less than 1/2 mile from the salt water, and normal factory paint usually gets 4 years before base steel starts to eat itself. Now on year 3 and there is not one pickle spot anywhere on any of the pieces. FWIW.

I also tried in on a patch of well stained old concrete...immediately followed by a neutralizer...and that patch looks sun baked white now 2 years later also...so it must be some mean stuff.

I bought a slightly used powerboat this year and the stern anchor was reported to be in the 'trunk' compartment under some massive fender (bumper) so it just got a check mark as being 'available' during the survey. Went to do some beaching on the barrier islands and...last guy has apparently put the stern anchor away wet! Big lump of rust, and the galvanized anchor chain looks welded by the rust! Since I'm life Steve Jeff on a lot of things...A new 175 buck fluke anchor with 4 ft of stainless bottom chain would make it all right in a heartbeat! Not me...lugged the anchor home...took off the chain using Kroil to get the shackle screws out...then wire wheeled the anchor itself to get crusty rust off, followed by an Ospho treatment, followed by a neutralizer wipe down. NO sticky the next day, bare spots now mellow. Did a cold galvanizing bucket soak...let dry in the Florida sun just before IAN came and anchor now good as new! Sure will have to see how it holds up but really does look great! The 4 ft bottom chain? I am encouraged to recycle that also, already did the shackles...but practicality says I will do that part in stainless because it is relatively cheap. Being me? I'm STILL going to do the old formerly galvanized bottom chain with the Ospho and cold galv....it will prob wind up as wall art....

Just a few examples...I think it is great stuff...I think you'd be better to dab it one rather than slosh...and DO pay attention to a neutralizing step before waiting 24 hours and moving along. I'd be tempered to try it on a hot tin roof, as I think the timing of neutrailizing is key based on my own experience...but I'd certainly defer to Scott Conger advice....

[Scott_Conger]

Jim

I keep a gallon jug for resupply, and a spritz bottle from any hardware store filled for whenever I need it. It will not decompose any portion of the spritz bottle so there is no worry there.

Now, I have always used it in no-wind, low-wind applications and have never had a problem but once...a small cloud of the stuff came back at me ONE time when I got carried away and it is an understatement to say that even a small amount of aerosol is bad for the lungs!

Over time, it will decompose scotchbright pads, so I have no doubt that it will decompose some brushes over time...it is not supposed to get on your skin, and will burn cuticles or cuts like crazy so utility gloves are a good piece of safety equipment along with eye protection and if you can stand it, a face mask.

Primarily, have something to mop up excess so that runs and splatters on ajoining bare shingles is minimized. It seems to have little effect on painted surfaces, so a judicious wipe occasionally on "good" shingles is prudent, while splatters on bare zinc should be wiped up ASAP within reason...it'll really FIZZ.

[jiminbartow]

Thanks to everyone for your help. Still trying to figure out what Pat said, LOL! Jim Patrick

[TXGOAT2]

Building flimsy housing rather than substantial housing capable of serving the needs of generations wastes lumber.

[TXGOAT2]

Would it be possible to remove the rust-affected shingles or sections of the roof and have them hot-dipped?

https://finemetalrooftech.com › pressed-pieces
Pressed metal shingles and panels....

[jiminbartow]

Pat. Absolutely not. Each individual 8” x 12” metal shingle (mfg. by W.F. Norman, www.wfnorman.com) locks into the shingle to its’ left and secured to the roof with two roofing nails on its’ right edge which is covered by the next shingle. Metal shingled roofs which were perfected in the 1800’s, last twice as long (50 years) as traditional fiberglass or asphalt shingles (25 years if your lucky). My roof has weathered 8 direct hits from hurricanes with no damage while every other traditional roof in the neighborhood has been replaced while mine, aside from a little rust, is still going strong. Much easier to coat it than replace it with something less durable. This next coating will last the rest of my life. Jim Patrick

[nicklm]

My experience with Ospho started years ago and when our 26 was stripped to bard metal in California it sat for a few years with no rust. It came to FL in 70's and started to rust as it passed over the state line. Rust stopped with Ospho and it provided the primer for painting. The fenders, splash panels and running boards were powder coated and the powder coating company did not want Ospho on the surface before they would do the powder coating. (Powder coating was another issue all together.)
I think is a perfect product for stopping rust before painting and have recommended it many times usually with great success. Caution if you use it near a mirror, it will damage the coating and continue even after trying to stop it from trying to rinse it away.
The next coating should be tested to see if Ospho could prevent bonding, I would think.

[Dave Young]

I use a lot of Ospho in my fabricating shop and whenever repainting a trailer or other steel items. I apply it with a typical pump-up sprayer for spraying round-up, cleaners or whatever. Warm temperatures definitely matter. It doesn't react at all under maybe 60 degrees. I wire brush the surface, spray the crap on and then after maybe 15 minutes, go at it with an airhose nozzle. The air blows any excess and/or puddles around to thin out the application. It seems to just blow off of painted or galv surfaces. I don't wipe anything. After 24 hours, I go ahead and paint. I've stopped sandblasting stuff like trailers and the results are just as good.

[jab35]

Jim: What would professional roofing companies in your area do to repair/restore your roof? You can't be the only person with this type of roof facing this problem. I would find out and go from there. Gool luck with your project, jb

[jiminbartow]

James. None of them want to coat it, they all want to replace the metal shingles with fiberglass at a cost of $20,000.00. Coating it myself will cost half of that and I will end up with a better, more attractive, more durable, historically correct roof for my 19th century house. Since metal shingled roofs, such as mine, are a rarity these days, the roofing contractors don’t have the experience necessary to coat the roof and my roof has such a steep slope (8-12 pitch), and is as slippery as a playground slide, none of them will touch it. Too dangerous I guess. Since I have painted it twice since 1985, I suppose I have as much experience as anyone else, but this time, instead of using an epoxy primer, I plan on using a rubberized roof coating called “Storm Shield”, made specifically for this type of roof, guaranteed for 25 years. Hopefully, if I do it right, and don’t get killed in the process , this will be the last time I have to do it. Jim Patrick

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[jiminbartow]

Thank you all for your help.

I wanted to run this by you to see if you think this would be a good list of procedures by which to spot treat the rusted areas of my roof with Ospho, keeping in mind that, with an 8/12 pitch roof is very steep and as slippery as a playground slide, so the procedures must be effective, but simple and kept to a minimum.

1. Scrub the entire roof with a solution of water, bleach and TSP using a long handled scrub brush to remove as much of the old oxidized coating, mold/mildew and dirt, as possible.

2. Coat only the rusted spots with Ospho, by hand, using a 1 1/2” polyester brush, making sure there are no runs and the Ospho is as smooth as possible and keeping the Ospho off of the unrusted areas bordering the rusted spots.

3. Allow to dry for 24 hours.

4. After the Ospho has dried, rinse with water and, using a soft bristled vehicle washing brush, scrub off the powdered residue.

5. When dry, wipe treated areas down with Mineral Spirits.

6. When dry, prime and coat.

Thank you.

Jim Patrick

[Scott_Conger]

No, I sure wouldn't rinse with mineral spirits and I would bet your coating doesn't want to see anything which leaves such a film

rinse and dry...yes
mineral spirits...no

please be careful...that whole job gives me the willies...out here we'd use a long reach forklift on huge tires to lift someone up there to work from a platform

[jiminbartow]

Thank you Scott. I’ll skip the mineral spirits. “United Rental” in Lakeland has a 45’ Genie bucket high lift that can be rented by the month for about $2,500.00 that is what I was considering renting to do the really steep portions but I will not rent it until I have all the areas I can reach from a ladder and from adjoining roofs done, because, while I have it, I also want to do some much needed repairs and maintenance work to my house. I’ll be careful. My wife insists.
Jim Patrick

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[Scott_Conger]

outstanding choice in equipment, but practice controlling that beast or you'll be working from inside the attic before you know it!

I will sleep better knowing this!

[RVA23T]

Hang your Christmas Lights before you return it!! Kinda jealous you get to play with the cherry picker!

[jiminbartow]

I agree. I painted my roof before and rented a high lift for a month about 25 years ago and they are a blast and easy to use. Jim Patrick