INVESTIGATION OF CORROSION INHIBITORS FOR FUMING NITRIC ACID. Period covered November 21, 1955 to June 7, 1957

Technical Report · Thu Sep 12 04:00:00 EDT 1957

OSTI ID:4342256

Bergdorf, W H; Kinsey, Jr, E J

Development of a corrosion inhibitor for fuming nitric acid that has corrosion-inhibiting and scale and sludge-formation properties superior to those of hydrofluoric acid was investigated. Amonium hexafluorophosphate in amount equivalent to 0.30% by weight hydrofluoric acid was found to provide better inhibition to the corrosion of 61S-T6 aluminum alloy and 17-7PH and AISI Type 304L stainless steels than 0.70% by weight hydrofluoric acid under the test conditions. Optimum inhibitor concentrations for Types I and III specification acids and inhibitor depletion rates for eight inhibitors including hydrofluoric acid were determined. Effects of inhibitor up to five times optimum inhibltor concentration of each of the several inhibitors were measured in terms of slush or freezing point of inhibited acid media which bad been subjected to wide variation in temperature and short time storage conditions. Measurements of the mechanical properties of welded specimen of the aluminum and stainless steel alloys that had been immersed in the liquid and vapor phases of eight inhibited acid systems for thirty days at 120 deg F showed that no significant change in properties was efected by these exposure conditions. Filmformation studies were conducted on aluminum and stainless steel specimens that had been exposed to the liquid and vapor phases of the several inhibited systems and subsequently rinsed in water and methylene chloride. Both rinses removed the inhibited acids from the specimens, but methylene chloride failed to remove corrosion products. Hydrofluoric acid, phosphoric acid plus hydrofluoric acid, and ammonium hexafluorophosphate at optimum concentrations dissolved in specification Types I and III acid media were tested in vessels fabricated from the aluminum and stainless steel alloys for a period of 60 days at 70, 120, and 160 deg F. Ammonium hexafluorophosphate produced the greatest pressures during the test period. This inhibitor, however, suffered the smallest loss in concentration and in general provided the best inhibition. (auth)

• Research Organization: Bell Aircraft Corp., Buffalo
• NSA Number: NSA-12-010582
• OSTI ID: 4342256
• Report Number(s): WADC-TR-57-302; AD-151116
• Country of Publication: United States
• Language: English

Related Subjects

ALUMINUM ALLOYS
AMMONIUM COMPOUNDS
CHLORIDES
CORROSION
FILMS
FLUORIDES
HYDROFLUORIC ACID
LIQUIDS
MATERIALS TESTING
MECHANICAL PROPERTIES
MINERALOGY, METALLURGY, AND CERAMICS
NITRIC ACID
PHOSPHATES
PHOSPHORIC ACID
STAINLESS STEELS
VAPORS
VESSELS
WATER
WELDS