It depends whether the citric acid will do the job. If it will, then it is a no-brainer - hydrofluoric acid is very much more dangerous than any other acid, so you should always look for a safer alternative. On the other hand, if it needs hydrofluoric acid to remove the contaminents, then you have to use it! Hydrofluoric acid in suitable concentrations can remove glasses; other acids won't.

According to their procedure to acidify the solution the dose with hydrofluoric acid to a concentration of 1% to dissolve the iron oxide scales and magnetite present.

Thanks all, Chris it was so informative.

HF is one of the most horrible acids I know of, where ever possible i never allow its use unless only in the most extreme of circumstances. http://www.hse.gov.uk/pr...coshh&cr=20-Mar-2013 http://emedicine.medscap.../article/773304-overview You say they dose the solution to 1% HF, what concentration HF are they dosing with? A skin burn from contact with diluted solutions of less than 20% concentration is characterized by pain and erythema (redness) with a latent period of about 24 hours. Delay of recognition of contact with diluted solutions often results in more severe burns because of the delay in washing or irrigation. The pain and erythema of the skin burn from contact with 20-50% solutions becomes apparent 1-8 hours after the exposure. When contact is made with concentrated solutions of above 50%, immediate pain and tissue destruction is apparent. There are various kinds of symptoms depending on the severity of the burn such as erythema alone, central blanching with peripheral erythema, swelling, serious burns, ulceration, blue-grey discoloration and necrosis. Systematic fluorosis may also occur with larger burns.