I had a look at Brownells MSDS sheet and found that Hydrogen chloride and Potassium Antimony Tartrate is used in the mix, not sure how the chemical reaction takes place or what its meant to do or how toxic it is, anyone know or if there are other ways. I was reading that the Black phosphate process is the most overlooked functional metal finish process around today. I had a chat to a Canadianicon company and they are looking for an agent to set up in Europe that sells the black phosphate process etc., anyone interested I can pass on details.