The stainless steel tubes have a 5mm internal diameter so i would like to use a chemical to clean them rather than brushing or sandingOriginally i thought the white substance was dried NaOH but HCl or water have not removed itNow i am thinking that it must be some kind of aluminium depositPlease help by identifying what may have formed or even better how to get rid of it
Aluminium metal reacts with NaOH to form a number of substancesThe most common is sodium aluminate, but it is also common to form the hydroxide - Al(OH)3This latter product is insoluble in water, but it should dissolve in acidThe choice of acid is a problemIf you are using type 304 stainless steel - or whatever the local equivalent is - do not use HCl because this grade of steel is atttacked by chloride ionsIf you are using type 316 stainless - you do not have a problem in this regardI suggest that you use H2SO4 to be safeYou need quite a concentrated solution of acid - so something like battery acid should be oKGive it time to reactI do not know what you were doing, but mixing NaOH with Al is not advisable, as you have discoveredAlso - unless you have specific training - be careful when dealing with concentrated acidsThey are dangerous.
