I will throw in my $.02 worth because I have been considering the same. All sheet metals are not the same. I used some cheap galv. from Ace hardware for a ground contact application and it did not last long (I am in a wet area). I am using a better grade of steel now for my roof and plan on finding a project to use up my leftovers, if any. The material I am using now is Galvalume which seems to resist rust better.(also reflects heat better) It is also 36" wide while the other was 24" wide. Both galvanized and galvalume will react with the copper in the treated wood. If I do go this route I will try to protect the metal with some type of coating, which may be paint, building felt or plastic, I have used driveway sealer, but the best thing I can say about driveway sealer is that it is cheap. To make long cuts like is shown on the link, your best bet is a friction disc. They come as an abrasive disc and a diamond coated disc, which will cost between 8 and 20 dollars. (all of these cuts can be made with metal snips if your hands are young enough to use them) A cutting torch would be nice, but I dont have one. I think you will need to shield the edges because the metal in so thin that it would be easy to cut yourself on. You will also need special nails or screws to work on this type of project. I like the idea of using the composite board, but I understand it is very costly. Larry

There's no harm in trying vinegar as your "mild acid". But first you must remove the oils and greases. The Holy Grail of metal cleaning is to get the metal to the point where "water has no tendency to bead." This mysterious state is very difficult to achieve by ordinary means. Orange oil will work, but NOT if it contains dyes as is usually the case. Hydrocarbons like acetone, BBQ fluid, gasoline (not!) are often recommended, though you may need some lite work after because they, too, often have dissolved oils. I finish (and start, in fact) with a "heavy duty degreaser" meant (I think) for restaurant grills based on 2-butoxyethanol. It;s cheap, like $7 a gallon. But regardless of the chemicals, the elbow grease required is also substantial. And the parts must not be touched with bare hands or with contaminated gloves. Also, any exposed steel will start to rust immediately after being cleaned in this way: watch out for threads if treating pipe fittings, consider greasing the threads immediately after drying. Once clean, the preferred acid is phosphoric. This is available as a wide range of products, meant for etch prepping galvo and many other uses. It's very cheap on a large scale, but you get reamed to one degree or another in gallons and less. I only needed a little, and found a dusty old 32 Oz. bottle of "rust remover" for $4.99. It was quite strong at %50, when I cut it 3:1 I had a gallon of 12.5%. It's not hard to pay $15+ a gallon for the brand name stuff. Any concentration in the range of %5-20 is commonly used. Figures of 5-15 minutes are usually given. For a large project, I'd use a low concentration and apply with a new (and degreased) all plastic, all poly sponge mop. The low concentration will give you time to assess what's going on before things get out of hand, and time to zap any drips onto inappropriate materials with the garden hose/sprayer. You don't need to neutralize it, but you do need to rinse it off thoroughly, don't let it pool or get into any holes/pipes/connector threads. How to know when to stop depends partly on the original finish. For thin, shiny electroplate as on "zinc plated" fasteners, remove immediately upon discoloration to grey: it may only take seconds. For sheet metal with a checkerboard appearance, you can use your finger in glove. Initially the (wet) surface will feel smooth. After a few minutes you should notice a significant change in texture, like fine sandpaper, or at least feel _weird_. When you start thinking to yourself "Hmmm! This is really doing something!", you can probably stop there, or let it go on about as long again. At least four things make phosphoric acid a good choice. It's biodegradeable, it doesn't fume, it's non-poisonous (used in food), and it won't eat through your concrete, much. But more interestingly, if it should happen upon some (iron/steel) rust, in theory it will convert the rust to a more passive, primeable, paintable surface compound that resists further corrosion. There are limits to it: the acid attacks the steel directly, and converts it more as an afterthought. So if it contacts the steel accidently, rinse it off immediately. Should a bit of rust form later before you get a chance to paint or oil it, a rub-down with the acid and a good rinse after is better than painting rusty metal. Oh, and for hot dipped galvanized? Cleaning is doubly hard: check the flammability and volatility of your degreaser, get it hot if suitable, and stew the parts for an hour or so. Small parts I sometimes submerge, when I'm satisfied it's had a good scrubbing bubble and appears a few shades lighter than at the start I rinse. For poles and conduit, I slop it on and rub it back and forth. up and down with a sponge, until it looks and feels right. Do you have to be so thorough and methodical to successfully paint galvo? It probably depends on how you define success. But in general, it's details like these that make the difference between a good, fair, or fail result by DIY'ers. Some people get the knack real quick, others seem to struggle forever. When it comes to surface treating, electroplating, and electropolishing of metals, the importance of proper cleaning can't be overemphasized. You should wear gloves and eye protection when doing any of this stuff: and while at low concentrations phosphoricic acid may lead to a bit of phosphate "blooming" of plant life, at the concentrations I've mentioned or with associated rinse water you should definitely expect it to burn your lawn.

I`ve used a product that called oxisolve, it works good you spray it on an let it sit. This stuff is safe and easy to use. One gallon with last a long time it`s on the expensive side around $30.00 for a gallon. But it looks like this is getting to be a yearly repair. they have new products for treating rusty surfaces, but this is the only one I`ve used. This is what the web site says about this rust remover This specially formulated Rust Remover is a powerful, rust-fighting liquid created to meet the needs of auto restorers. It reaches even inaccessible areas, quickly dissolving iron oxide completely and leaving a zinc phosphate coating. Rust Remover can be sprayed, brushed, or used as a parts dip. It is non-toxic, non-flammable and reusable. I just used it to remove rust from a expensive commercial lawn mower deck, It`s treated now and just needs paint.Nice and smooth surface all the heavy rust deposits are gone.I also used it the treat a running board from my wifes grandfather model TT ford truck that was rusting away. It`s now painted satin black with wrought iron shelf brackets she uses it for her angel collection, looks nice on a wood paneled wall. Here is a link that might be useful: Eastwood

Early last summer I painted a metal porch roof that's about 45 years old. (Galvanized but it had some patches of rust.) I used Ben Moore's IronClad Low Lustre Metal & Wood Enamel. I used the Latex, I had used it the prior year on metal siding on an outbuilding and was impressed with application, appearance and a year later it still looks fresh and new. Rusty areas I patched with Rustoleum oil-based primer for heavy rust. But I prepped well, sanding with a wire disc on a drill to get as much of the rust off as possible, then wiping with mineral spirits. Not sure about longevity of the roof yet, it's only been about 6 months, but did take a beating from hot late summer sun this year, still looks good and fresh so far! (I used a light gray on the roof, they can custom mix any color from their line.)