surfRenegade wrote:
Went to Lowes last night to get material for my cross bars I am making. I am looking at 3/4"diameter. I guess I have to buy a 10' because I need over 7' of material it looks like. My question is, there where two different types, one was galvanized steel, the other black iron. Whats the difference? They both were pretty heavy when I picked them up. Is it necessary to have that thick of walls?
Black Pipe is a type of cast iron typically used for natural gas and propane lines in homes and businesses. It's very tough and takes a lot of abuse, but it's not really meant to be "strong" the way a structural member would. It's intended to maintain its integrity as a vessel for a volatile gas or other fluids (i.e. keep the gas in, the contaminants out, and stay where it is for a long time with minimal fuss). It's also really heavy and rather ugly.
Galvanised steel conduit/steel is usually a mild steel alloy with a protected zinc coating impregnated in the outside (by heat or electricity) that forms an oxygen barrier and prevents corrosion. Typical galvanised conduit you'll find at the big box store is for use with electrical runs and is meant to protect wires from damage. It's not meant to be all that strong as it's usually really thin-walled.
Either would technically work in a pinch, but neither is really ideal for what you're doing. Have you tried a local steel scrap/recycler to see if they have some scrap steel tube the length diameter you need? Unless it's bent or really badly corroded, steel tube cleans up nicely with a grinder or sanding (depending on your level of elbow grease) and a good coat of rustoleum.
Dan
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