Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
  • C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
  • C23F11/18—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids using inorganic inhibitors
  • C23F11/182—Sulfur, boron or silicon containing compounds
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
  • C23F11/04—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in markedly acid liquids
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31652—Of asbestos
  • Y10T428/31656—With metal layer
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31652—Of asbestos
  • Y10T428/31663—As siloxane, silicone or silane

Definitions

• Oxidizing acid media especially nitric acid, aqua regia and chromosulfuric acid, do not, or only slightly attack titanium and titanium alloys even at temperatures exceeding 100 C., when acting in the presence of silicon or siliceous substances.
• the anticorrosive effect is observed in practically all siliceous substances, even in those known to be inert towards oxidizing acid media.
• the corrosion attack in the vaporous phase is particularly avoided by vaporizable or sprayable siliceous compounds.
• the present invention provides a process for protecting titanium and titanium alloys against the corrosion caused by oxidizing acid media at temperatures exceeding 100 C.
• oxidizing acid media there are, in particular, understood nitric acid and mixtures of nitric acid and hydrochloric acid, so-called aqua regia, moreover the mixtures of concentrated sulfuric acid and chromic acid, known as chromosulfuric acid.
• Oxidizing acid media of this type vigorously attack titanium and titanium alloys which may especially contain aluminum, vanadium, molybdenum and palladium, at elevated temperatures, in particular at temperatures exceeding 100 C.
• the oxidizing acid medium contains, for example, quartz sand or glass powder.
• the protection is even more effective in the presence of siliceous compounds which are less inert.
• Compounds of this type are, in particular, precipitated silicic acid, iron silicide, alkali metal silicates. kaolin and asbestos powder. It is a matter of course that elementary silicon is also effective.
• Silicone oils are particularly suitable for carrying out the process of the invention since they are easy to handl-e and to dose and since their handling involves no hazards.
• the amount of siliceous substance is not critical.
• the spaces to be protected should, however, always contain such an amount of siliceous substance that, per square meter of the surface to be protected, 10 milligrams of silicon are present, when siliceous compounds are used, it should be an amount equivalent to that of the silicon.
• the silicon level may be maintained by a continuous or portionwise feed.
• non volatile siliceous substances can be added to the oxidizing acid medium in an excess sufiicient to do without a feeding over prolonged intervals.
• Example for the corrosion tests tubes of pure titanium were used which served as testing vessels and as corrosion samples simultaneously. They had an inside diameter of 20 mm., an inner height of mm. and an inner surface of 97 cm. One end of the tubes was closed by welding with a pure titanium plate. On the other end the tube was closed so at to be gastight by means of a metal cover and a sealing plate of polytetrafiuoroethylene with the use of a clamping device.
• the titanium tubes were filled to about /5 of their height with the corrosive medium, placed in thick-walled steel containers and heated at the required temperature in a furnace with circulating air. The temperature was maintained constant by means of a regulator.
• Tables 1, 2, and 3 are indicated the test results obtained, i.e. the anticorrosive effect on pure titanium against nitric acid and mixtues of nitric acid and hydrochloric acid.
• Table 2 contains the experimental data with respect 3 to the stability of pure titanium towards HNO with different additions under varying conditions.
• V stands for vaporous phase and L for liquid phase.
• the plus means that no corrosion could be observed.
• the minus indicates that the nitric acid condensed in the vaporous phase did attack the metal.
• the corrosion velocity in each case was about 2 millimeter per annum, corresponding to the value indicated in Table 1 for an about 30% nitric acid at 100 C. to indicates that the protection was not uniform, some spots of the metal surface having been attacked.
• Table 3 indicates the linear corrosion velocity of titanium under the action of mixtures of nitric acid and hydrochloric acid of varying concentrations and at different temperatures and illustrates the anticorrosive effect obtained by carrying out the process according to the invention.
• the weaker anticorrosive effect obtained in Tests Nos. 11 and 14 is mainly due to the fact that glass powder and quartz powder are attacked to a very small extent only by nitric acid so that the protection develops only slowly.
• a phenyl-methyl silicone oil was used; density 1.02 g /co., viscosity 200 centistokes at 25 0; thermal stability in air at 250 0. 1,000 hours.
• titanium alloys For the tests with titanium alloys corresponding metal samples were placed into the specified tubes of pure titanium. Tests were carried out with the following alloys: titanium with 6% of aluminum and 4% of vanadium, titanium with 5% of aluminum and 2% of molybdenum, and titanium with 0.2% of palladium.
• a process for protecting titanium and titanium alloys, having as an alloying component aluminum, vanadium, molybdenum or palladium with the base metal being titanium, against corrosion by a strong oxidizing acid medium at temperatures exceeding 100 C. which comprises allowing the oxidizing acid medium to act upon titanium or titanium alloys in the presence of silicon and a siliceous substance selected from the group consisting of iron silicide, Si .xH O, quartz, sodium silicate, calcium silicate, glass, kaolin, asbestos, SiCl halogenosilanes, and silcone oils.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Paints Or Removers (AREA)

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Citations (10)

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• 0
  • GB GB1052064D patent/GB1052064A/en not_active Expired
  • NL NL299448D patent/NL299448A/xx unknown
• 1962
  • 1962-12-07 DE DEF38483A patent/DE1300416B/de active Pending
• 1963
  • 1963-12-09 BE BE641012A patent/BE641012A/xx unknown
• 1967
  • 1967-04-04 US US628268A patent/US3457103A/en not_active Expired - Lifetime

Patent Citations (10)

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