PRODUCTION W a r O n Scale Turco and Temco find n e w w a y s to descale titanium. One is chemical, the other electrolytic JL w o N E W PROCESSES m a y take some
headaches out of descaling titanium. O n e is a chemical method (C&EN, Jan. 14, 1957, page 7 8 ) offered b y Turco Products, Los Angeles. T h e other, an electrolytic method (U. S. Patent 2,780,594), comes from Temco Aircraft Corp., Dallas. Both are said t o h a v e a goodly edge over present descaling methods: molten salt baths, sand or vapor blasting, a n d acid pickling. Turco's process is for u s e after hot forming or heat treatment. It can serve also t o prepare titanium for welding or simply to improve surface condition. It satisfactorily removes oxides formed a t heat treat and annealing temperatures on all titanium alloys known to date, says Turco, and is n o w in commercial use. Briefly, t h e process works like this: • Scale conditioning: Turco 4 3 1 6 in water, 275° F., 10—15 minutes for oxides formed below 1200° F . , 4 0 - 4 5 minutes for oxides formed above 1200° F . • Cold water rinse, 3 - 5 minutes. • Scale removal: Turco 4272 in 2 5 - 3 0 % nitric acid, 145° F . , 5 - 1 0 minutes.
• Cold water rinse, 2 - 3 minutes. • Pressure spray rinse. T h o u g h Turco will not give detailed chemistry of its process, it does say t h a t chelation is involved. It says, also, t h a t T u r c o 4 3 1 6 , a strongly alkaline comp o u n d , reacts with scale oxides to m a k e t h e m m o r e soluble. And Turco 4 2 7 2 combines surface activity with fluoride ions. U s e of a fluoride salt in nitric acid to descale titanium isn't new, b u t normally you get rapid release of t h e active ingredient. Turco 4272 is buffered t o give controlled release, t h u s holds metal loss to a minimum. While Turco's process doesn't r e q u i r e pretreatment, used often t o inhibit oxide formation, it does call for precleaning. Otherwise, surface contaminants m a y alloy with t h e titanium d u r i n g h e a t treatment, making resulting oxides tougher t o take off. Low metal loss, absence of intergranular corrosion, a n d little or no h y drogen pickup are strong points of its process, says T u r c o ; these are n o t readily attained in molten salt baths, s a n d or vapor blast, and acid pickling. Also, t h e process reduces w a r p a g e of thin gauge metal. I t works a t a t o p
Temco Aircraft's descaling process is electrolytic, is used after h e a t treatment a n d fabrication. H e r e , J. J. Dailey ( l e f t ) , Temco supervisor rug Manufacturers Association.
