Soldering has been common practice in the metal roofing trade to ensure water tight joints and to strengthen seams. While some purists may frown upon using solder to mend together two pieces of metal, there is one thing for sure…the practice of soldering isn’t going anywhere in our trade. While very common, soldering can be a bit tricky for a beginner.
Check out this list of 8 common roofing materials and its “solderability” in the field:
Copper is one of the most easily solder-able metal available. When soldering copper, 50/50 lead-tin solder is preferable and a multitude of fluxes are available. Generally, Ruby Fluid works fine for new copper soldering, but if you are having issues, try a flux specifically made for copper. It may help to pre-tin the sheet edges to facilitate soldering.
Copper does not react with water but it does slowly react with atmospheric oxygen (patina) to form a layer of brown-black copper oxide which, unlike the rust which forms when iron is exposed to moist air, protects the underlying copper from more extensive corrosion.
2) Copper Plus (Copper Coated Stainless Steel)
Copper Plus is a copper clad stainless steel trademarked by Heyco Metals. This material is known for the high strength of stainless while providing the preferred aesthetics of copper at less of a cost. In simpler terms, it’s stainless steel bonded by a top and bottom layer of copper.
Copper Plus can be soldered very similarly to copper. Mild fluxes should be used and one must neutralize the seam immediately after soldering.
Sorry folks, Galvalume CANNOT be soldered. Galvalume is a steel roofing material that features an alloy coating of 55% aluminum-zinc. It’s an ideal material for roofing because of its extraordinary outdoor corrosion resistance and resulting long life. It is not recommended to abrade the surface to expose the aluminum-containing metal layer before soldering. This will void the warranty.
4) Galvanized Steel
Often people will say they are “working with galvanized” and we generally assume that this implies galvanized steel. FYI, to galvanize something is simply to coat (iron or steel) with a protective zinc layer. Galvanized Steel can be soldered as long as the zinc coating is removed. Try taking a wire brush to the material to get it bare. Once the coating is removed, use 50/50 or 60/40 lead-tin solder and try the Johnsons flux for Galvanized metals. Neutralize the seam after soldering
5) Lead Coated Copper
Lead coated copper will benefit from the added strength of using a 60-40 lead-tin solder. The higher the tin content in the solder, the higher the tensile/shear strength will be. Excessive fluxing should be avoided and be sure to neutralize the seam after soldering.
Lead coated copper does not extend the life of copper. Its purpose is to provide an alternative color to architectural copper applications.
6) Stainless Steel
Contrary to popular belief, stainless steel can be soldered. It benefits to use a stainless steel flux that is quite corrosive. It is also recommended that the soldering iron is kept slightly cooler and spends a longer time contacting the metal on the seam. Neutralize after completing the seam.
Stainless steel does not readily corrode, rust or stain with water as ordinary steel does.
Zinc is a material in the United States that will see growth in the years to come. The two biggest manufactures of Zinc are Rheinzink and VM Zinc. Zinc can be soldered and 50/50 or 60/40 lead-tin solder is acceptable. There are particular fluxes that work best with Zinc such as Express Zinc Flux. Here are VMZinc’s full soldering instructions in PDF format.
8) Freedom Gray (Zinc-tin-coated copper)
One of the great parts about working with freedom gray is that it solders just like copper. Remove all coatings (wire brush) and apply flux. Note that zinc melts at 784° F and solder begins to flow at 420°F. If too much heat is applied, a hole can easily be burned through the zinc.