Corrosion Resitance of 99.5% Aluminium

[DEGS2]

Good day anybody.
I posted this query in Mechanical Eng but in hindsight this may not get me any responses since its more a "metal micky" problem than a "metal basher's".
I am currently designing a 98% Nitric Acid Storage Vessel as a horizontal vessel on support rings. Shell material is 99.5% aluminium. I intend to manufacture the vessel support rings in 5083 aluminium due to its superior strength and weld the rings direct to the 99.5% Al vessel using 5356 consumables. The tank wall is 14mm.
Will the corrosion resitance of 99.5% Al be effected by the direct external welding of the 5083 Aluminium rings?
Should I add a 99.5% Al dillution plate between the 5083 rings and the vessel wall?

Its almost 10.00am here in Falkirk, Scotland the weather is dull and dank. Hope the sun has got his hat on where you are.

All comments/advice appreciated.

 

[metengr]

DEGS2;
From what you described and information I reviewed, I don't see a problem with fillet welding the AA5083 shell stiffeners directly on the AA1050 shell material. The AA 1050 is not heat treatable, and given that the welding is on the exterior of the shell and the shell thickness is 14mm, I do not believe that the heat from welding to the exterior surface will adversely affect the shell interior surface exposed to concentrated nitric acid. Keep in mind that girth and/or seam welds (with heat generated) are done on fabricated aluminum tanks.