Yesterday I was running errands and stopped at a store that carries a very large selection of various cleaning products. Perhaps one of the largest selections of types, brands, and applications I've seen in a long time. I searched through many of them, looking at their labels for contents/ingredients and intended uses. A couple of interesting findings....
In another thread "Hasbro" mentioned the use of "Bar Keepers Friend" cleaning powder for rust removal on surfaces:
https://xwebforums.com/forum/index....-powder-cheap-rust-remover.35851/#post-311115.
The principle ingredient is Oxalic Acid, which we have discussed here as well. At the store I noticed there are a couple versions of that cleaning product. The dry powder as referenced, a cream 'polish', and a liquid cleaner. All have Oxalic Acid as the main ingredient, but the liquid one also has Citric Acid. That is another of the acids noted for scale removal when I was searching the topic. I assume these household cleaners are very weak versions of the acid(s). But the mixture of the two types (oxalic and citric) in the liquid version is interesting. The price for a bottle of the liquid was around $4, and a couple bottles might be enough to fill the just coolant passages. Although I think it is too weak for our use.
Coffee pot cleaners vary considerably in their contents. At least one had Oxalic Acid as its key ingredient and some had Citric Acid, while others use a base (more on alkalines later). No idea just how strong these solutions are.
Some cleaning products for toilets, hard water deposits, lime, etc use acids like Hydrochloric, Muriatic, and Sulfuric. Again, I assume they are rather weak solutions of those acids because they are very strong otherwise.
Some drain cleaners also have strong acids like those above, another uses lye which is a strong alkaline. According to what I read previously, acids should work better for scale than bases.
I suppose some of these products are easily available sources for some agents that might work to clean the scale out of a head. The problem is their labels do not say how much of the acid(s) or what dilution they contain. I assume all of them are very weak. And frankly many of them are very expensive for their quantity. So I think it is better to stick with buying the actual ingredient (eg. acid) of choice and mix it to your preferred solution strength. I remember one of my intro chemistry professors saying that most household cleaning products are just really expensive dilutions of an otherwise inexpensive chemical.
I also looked around for other sources of Oxalic Acid. It is a common wood cleaner ("wood bleach") in some areas, but not around here (where there is zero humidity and therefore no wood staining). The local paint store carries a liquid version of it mixed with water, but the label does not specify the percentage or strength. And it was very expensive. In the past I have purchased straight Oxalic Acid in powder form online for a reasonable cost (but it isn't super cheap). At least that way you know what you have based on how you mix it.
Not many places carry the old "Naval Jelly" rust remover anymore, especially not the one for aluminum. One hardware store had both versions (for steel or aluminum). Both labels say the key ingredient is Phosphoric Acid, which is a well know rust remover. I imagine the one for aluminum use is just a weaker solution of the acid? But it might have other buffers to protect the aluminum from too much corrosion. A fairly small bottle was around $6, and it would probibly take at least four or more bottles to fill the coolant passages. Not super cheap but also not too expensive compared to some of the other options. The thickened 'jelly' form of the acid might be easier to fill the coolant cavities without getting it all over the rest of the head (I think). Maybe it could be 'injected' into the passages with a huge syringe or something? No idea how well it works to remove the scale and deposits. It may still be too weak for this use.
I filtered the used, weak phosphoric acid I have. Took forever due to the heavy contamination. It should be good enough to experiment with on my trash head. If it looks promising then I'll look more at the phosphoric options. Otherwise Oxalic Acid is seeming more promising, based on the research and the labels I saw at the stores (for their intended uses). I still have some of it to test as well. Should be able to get some results in a few days.
