That sounds about right. That crap is strong stuff but it can be cut with water. use very little acid and lots of water.
the only problem it that if you put that sending unit in and kind of acostic dip you are going to strip that pretty coating off of the rest of the unit. Every thing that fits inside the tank has a zink/cadium coating on it and it is not hard to strip off.
Once that coating is gone you can just sit there and watch the metal rust.
Also you really have to rins the parts after you use something like muriatic acid because if you don’t it will just keep on desolving what ever it is on.