Development of Free Nitric acid, Non-P Desmut Solution for Surface Treatment Aluminium Alloys

The purpose of this study is to develop non nitric acid desmut to cope with environment regulation and at the same time, to obtain the effect comparable to nitric acid in removing smut. For this, some desmut solutions were produced adding 2~3 chemical reagents to basic components such as peroxide, ammonium group, ferric group compounds and acid. And, electrochemical treatment was tried to remove ammoniacal nitrogen(NH3-N) in desmut solution after desmut treatment. Consequently, we could gain smut-removing ratio of 90% using the solution mixed with peroxide, ammonium group, ferric group compounds and sulfuric acid at 35°C for 70 seconds, and the ratio is almost the same with that using nitric acid type desmut solution. In this work, most nitrogen(T-N) was confirmed to be ammoniacal nitrogen(NH3-N). In addition, we succeeded in controlling ammonia-nitrogen below 60 ppm corresponding to environment regulation by electrochemical treatment in the wastewater.