descaling used galvanized pipe?

I'd suggest diluted muratic acid, maybe 10:1. leave a leak at the downhill end of the pipe. Fill at the top. It may take a lot of acid, but its only $2/gallon. Flush with drain cleaner (or any other base) diluted in water after flushing with plain water when done to stop future corrosion.

Muratic acid is commonly used. It will also dissolve the galvanizing unless it is "inhibited" or "killed". This type is saturated with zinc and is used for swimming pool PH adjustment, fluxing galvanized roofing for soldering, and for descaling. If you have one available, check at a place that sells chemicals for steam cleaners.

Don Young

I would consider finding some bore brush, like they use on guns, with rope on both ends. You can use a buddy to pull from two sides. I use one like this on my rifles. You can use some water and soap also, and then flush with a garden hose and then maybe compressed air when they dry. They just have to be clear of debris, and scale, right?

The muriatic acid idea is also a good one.

Fill each with a slury of sand and water, cap both ends and spin each in the lathe overnight.

You can use common nilon round pipe cleaning brush and ' Sulfomic Acid ' a white salt like substance cheap and available in chemical stores. Sprikle little 1 -2 tea spoonfull Sulfomic acid inthe pipe and with the help of the brush clean the inner surface. This acid is very mild and do not damage clothes like muteric and do not react with Zinc.

You will require 1/4 Lb to 1/2 lb of sufomic acid to clean a 20ft long pipe depending on salt deposit on zinc surface. I have cleaned radiator tubes and GI pipes sevreral times tis way.

Tipu

I think maybe you mean sulfamic acid. Interesting - I can actually buy the stuff. In searching for Aqua Mix, I discovered you can buy phosphoric acid by the gallon for $15.88 online.

Grant