[Lynn Eades]

I'm no expert here but on hydrogen embrittlement, If you have an item that has been chrome plated , and you re chrome it you will severely weaken it as the process brings hydrogen to the surface of the metal which weakens the metal just as bringing nitrogen to the surface toughens it as in "nitriding"- dont re-chrome structural stuff like suspension/steering components.
Phosphoric acid is a food preservative. it is very good for cleaning ferrous metal (steel) Its probably the active agent in the HPsauce. If your going to use it talk to an industrial chemist first.
In an Impco book I read an article about how important it is to have good heat transfer from an engine block to the coolant, direct rather than through a layer of rust scale. The article reccomended cleaning the engine block out with muriatic acid, Which I understand is a particular strength of phosphoric acid to which an inhibitor is added to stop the acid continuing, once it has broken down the scale. I found it worked very well.
If you set up an acid bath with phosphoric, dont put cast iron or high carbon steel in it or every thing you put through it after that comes out black.
The great thing about any of the methods used in this thread is that they chemically stop the oxidation process whereas the purely mechanically process of blasting doesn't.
My carrier with its particular type of steel floor was quite rusty, the blasting took hours and hours because each little rust hole seemed to turn into a rust cavern inside, and although it was painted straight away the rust has re appeared. Because this has proven to happen quite a bit, I now like to combine mehanical and chemical cleaning. ....A great thread, Thanks guys.