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
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/73—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process
• • 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
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/68—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous solutions with pH between 6 and 8

Definitions

• This invention relates to a method of treating steel stocks under pressure and has an object to provide protective coatings having excellent corrosion resistance comparative to that of zinc plated sheet when immersed in water.
• a method for protecting the surface of steel stock against corrosion comprising a calcium or magnesium molybdate solution, an alkaline solution of magnesium oxide, a sodium sulfide solution containing a calcium or magnesium molybdate, or a sodium sulfide solution.
• Steel sheets are immersed in one of said solutions contained in an autoclave maintained at a temperature of from about 240 C.
• the sheets can be immersed thereafter in chromic acid, if required.
• steel sheets are formed on the surface of steel sheets, these iron compounds cooperating to provide excellent corrosion resistance. Since the surface condition of the films varies dependent upon the pressure and since the films are porous, steel sheets can be subjected to an after treatment by dipping them in a chromic acid solution. Sodium sulfide solution incorporated with a small amount of M.Mo0 results in oxides or sulfides similar to those formed by said sodium sulfide solution in addition to compounds of molybdenum and alkaline earth metal, thus further increasing corrosion resistant properties. In each of these cases, it is advantageous to after-treat the products with a chromic acid solution.
• Example 1 TABLE 1 Sample numbers Conditions 1 2 3 4 Temperature, C 240 285 325 385 Pressure 38 70 300 TESTS IN ACIDIC SOLUTIONS Test pieces shown in Table 1 were immersed in solutions of various pH values of from 2 to 7. It was noted visually that in a strongly acidic solution of pH 2 the surface film of each of test pieces 1-5 was dissolved in about 24 hours. However, after this time, weight loss of Samples 2-5 thereof was smaller than that of untreated cold rolled steel sheet (Sample 1) which demonstrated that corrosion resistance was influenced substantially by pressure and heat. These test results are shown in Table 2 below.
• Example 2 This example shows the results of treating cold rolled steel sheets in accordance with thisinvention followed by an after treatment with an aqueouschromic acid solution.
• the steel sheets were treated in a 0.25 mol aqueous solution (Na,S:1.95 wt. percent) of sodium sulfide at a temperature of 325 C. and under a pressure of 1 10 atmospheres pressure for 24 hours, and then treated in a chromic acid solution of a concentration of 0.3 to 2.0%.
• Corrosion tests were performed by immersing test pieces in a running water tank of the dimension 100 cm. x 100 cm. x 50 cm. through which water was circulated at a rate of 125 cc./min. to determine the weight loss by corrosion.
• Example 3 This example shows comparison of results obtained by treatingwith above described various solutions.
• Table 5 shows the conditions of surface corrosion after standing for 30 days in a warehouse.
• Sample No. 1 is a steel sheet treated with an aqueous magnesium molybdate solution (MgMoO 4.6 wt. percent).
• Sample No. 2 is a steel sheet treated withan aqueous calcium molybdate solution (CaMoO 3.2 wt. percent).
• Samples No. 3 is a steel sheet treated with an alkaline aqueoussolution of magnesium oxide (NaOI-I: 1.85 wt. percent; MgO: 1.85 wt. percent).
• Sample No. 4 is a steel sheet treated with a chromic acid solution (CrO 2.0 wt. percent).
• Sample No. 5 is a steel sheet treated with an aqueous sodium sulfide solution containing a small quantity of magnesium molydbdate (MgMo0 0.5 wt. percent).
• Sample No. 6 is a steel sheet treated with an aqueous sodium sulfide solution (Na S: 1.95 wt. percent).
• Sample No. 7 is an untreated cold rolled steel sheet.
• Table 6 below shows conditions of surface corrosion after standing 7 days.
• Example 4 Cold rolled steel sheet was treated with an aqueous sodium molybdate solution (2.0 wt. percent) or with an aqueous magnesium molybdate solution (1.8 wt. percent) at 280 C. under a pressure of 100 kg./cm. for 24 hours.
• this invention provides highly corrosion resistant protective films on steel stocks by immersing them in a solution selected from a molybodate solution, such as a calcium molybdate solution (.l3-6.42% by weight) or a magnesium molybdate solution (0.18-9.21% by weight), a mixture of magnesium oxide solution (0.4-8% by weight) and alkaline solution such as a sodium hydroxide solution (O.4- 8% by weight) or a potassium hydroxide solution (0.56-l1.2% by weight), a sodium sulphide solution (0'.39-7.8% by weight), or a sodium sulphide solution (0.39-7.
• a molybodate solution such as a calcium molybdate solution (.l3-6.42% by weight) or a magnesium molybdate solution (0.18-9.21% by weight
• a mixture of magnesium oxide solution 0.4-8% by weight
• alkaline solution such as a sodium hydroxide solution (O.4- 8% by weight) or a potassium hydroxide solution (0.
• Method for protecting the surface of steel stock against corrosion which comprises immersing said surface in an aqueous solution selected from the group consisting of a solution consisting essentially of from 0.13 to 6.42 percent by weight of calcium molybdate and water, a solution consisting essentially of from 0.18 to 9.21 percent by weight of magnesium molybdate and Water, an alkaline solution consisting essentially of 0.4 to 8 percent by weight of magnesium oxide, an alkali and Water, and a solution consisting essentially of 0.39 to 7.8 percent by weight of sodium sulfide, a calcium or magnesium molybdate and water wherein there is 0.13 to 6.42 percent by weight of calcium molybdate or 0.18
• magnesium molybdate a solution consisting essentially of sodium sulfide and water, at a temperature of from about 240 C. to about 400 C. and a pressure of from about 40 to about 300 kg./cm.
• aqueous solution is a sodium sulfide solution containing magnesium molybdate.
• aqueous solution is a sodium sulfide solution.
• aqueous solution is a sodium. sulfide solution containing calcium molybdate.

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• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Treatment Of Metals (AREA)

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• 1967
  • 1967-02-18 DE DE19671621499 patent/DE1621499B2/de active Pending
  • 1967-12-14 GB GB56846/67A patent/GB1195990A/en not_active Expired
  • 1967-12-18 FR FR1549749D patent/FR1549749A/fr not_active Expired
• 1970
  • 1970-10-01 US US77372A patent/US3701693A/en not_active Expired - Lifetime

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