any acid based cleaners are going to eat the steel or at least components out of it. Given the cleaning agents you are using are comparatively mild, are not in super strength or sitting for a long time, it will probably be minimal. For what its worth, any caustic / alkalii / basic.. based cleaners have the ability to do the same, especially on aluminum.
If your problem is scale buildup then yes an acid base is probably going to a bit better on it, if your problem is organic buildup ie grease / oils / gunk, then a alkaline base will probably work better for you. For the non chemists out there, alkaline base is the opposite of the spectrum of acid based.
A powerful drain cleaner is mostly sulphuric acid, a very strong acid base, the opposite of that spectrum would be to use Lye. Both will tear up metals real good, especially aluminum. Do not EVER mix them.
One thing I have found that works good is Sodium Carbonate, its mild enough not to tear stuff up yet will get grease and gunk out. You can get a small 4-6 ounce bottle of the brand name 'brew rite' for about 4 bucks. Or you can goto the pool cleaner isle and it's called Ph ADD by Aqua Chem and a quart bottle will cost about the same. Same ingredient.
Rinse several times after cleaning and you should be fine.
Aaron
