I tried muriatic acid to de-rust some bolts, worked great. Thought about soaking a rusty NH carb but the float hinge part that is riveted on is brass. Will the acid attack the brass?
It will but not nearly as much as it will eat at the cast iron. If you use it,and I recommend you don't,you will have to neutralize it with baking soda bath to stop it from eating a hole in the carb body. Media blast it and eliminate the problem.
OK, I'll blast it. Sometimes easier is not better, figured I'd ask before I messed it up. Thanks.
I use muratic to clean brass but usually brass lights. It will take it to clean brass in nothing flat (nothing flat = about 2 to 3 minutes). My guess is it attacks the zinc in the brass. (I've stuck a piece of pot metal in the acid and it really makes it bubble.) So, if you are dunking the whole carb in the acid, you may not have any brass left when the cast iron finally becomes rust-free. When the brass comes out, it will still look black but just rinse it off and use your fingers or tooth brush style wire brush to clean the black off. It will look like a new brass sheet. The acid I use is very mild. I've done this for years (my acid is about 38 years old now) and have had no problems with the brass afterwards but again, I only leave brass in a couple of minutes. I would start out with some water and add a litle acid to try it. If you need to add more acid, you can. See the caution below about the acid...
From “General Chemistry Online”
Why is acid always added to water, and not the reverse?
A large amount of heat is released when strong acids are mixed with water. Adding more acid releases more heat. If you add water to acid, you form an extremely concentrated solution of acid initially. So much heat is released that the solution may boil very violently, splashing concentrated acid out of the container! If you add acid to water, the solution that forms is very dilute and the small amount of heat released is not enough to vaporize and spatter it. So Always Add Acid to water, and never the reverse.
PLEASE USE CAUTION WHEN USING ACID
Wear protective clothing to keep the acid off of your skin. Wear a face shield. Work with acid outdoors. Keeping a bucket of acid in your shop will rust everything up! Acid should not freeze in our climate. Don’t breath the fumes. Don’t let the fumes from acid accumulate. They are rich in Hydrogen, which, in certain concentrations, is highly flammable. Just a spark can set it off (remember the Hindenburg…it was a hydrogen filled dirigible). So, don’t weld or grind over a bucket of acid.
DO NOT use muriatic acid to clean any ferrous metal. Initial results will look good, but it can keep slowly eating away for decades. Baking soda will not neutralize the acid that gets into the grain of the metal. There are industrial metal cleaning and stripping processes that use acids and neutralizers to achieve the same results, but they are very specific chemicals and processes which are monitored for just the right PH, etc. in order to get acceptable long term results.