Summary for nitric acid changed colour Discussion
The thread on nitric acid changed colour of aluminum sheet centers on a coil/anodizing job where a particular lot was cleaned in caustic soda and then apparently showed an unexpected colour change after an overnight nitric acid dip. The excerpt provided does not include the full diagnosis or final remedy, so the safest takeaway is limited: the issue appears tied to that specific lot and to the cleaning/deoxidizing sequence rather than to a general nitric acid effect on all aluminum. The visible response text only identifies Ted Mooney, P.E., and the context suggests the discussion was about process troubleshooting in anodizing preparation. Because the full answer is not present in the excerpt, no firm corrective action can be attributed beyond noting that the problem was lot-specific and process-related.
Q. Dear Sir,
Good Day,
Sir, once again I am here. Recently I took a lot of anodising. This coil job first was cleaned in caustic soda ⇦liquid caustic soda in bulk on
Amazon [affil link]
. After rinsing it was dipped in dilute nitric acid for neutralising. After overnight dipping (which was by mistake), in the morning I found that the colour of the nitric solution became golden. It is not the same for other lots. Whether there is any particular problem with aluminium sheets we do not know.
Please help. How to retrieve nitric to original.
S. Tambe
Hobbyist – Raipur, Chhattisgarh, India
April 6, 2012
A. Hi, Tambe.
Sorry, but I can’t quite be sure whether you are saying that the aluminum became yellow or the dilute nitric acid became yellow. But if it is the nitric acid, your only practical option seems to be to treat and discharge it and replace it.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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April 6, 2012