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
  • C23F3/00—Brightening metals by chemical means
  • C23F3/04—Heavy metals
  • C23F3/06—Heavy metals with acidic solutions

Definitions

• the present invention relates to the composition of baths for the chemical polishing of stainless steel surfaces.
• Chemical polishing of metal surfaces is a technique well known (electrolytic and chemical polishing of metals - W.J. Mc G. TEGART - Dunod - 1960 - p. 122 and following); it consists of treat the metal surfaces to be polished with oxidizing baths.
• baths generally comprising a mixture, in aqueous solution, of hydrochloric, phosphoric and nitric acids.
• suitable additives such as surfactants, viscosity regulators and brightening agents.
• Patent application EP-A-0 206 386 proposes to solve this problem using polishing baths consisting of hydrochloric acid, acid nitric, phosphoric acid, ferricyanide complex ions and an additive capable of breaking down nitrous acid.
• the invention aims to provide polishing baths without phosphoric acid designed to perform slow and efficient chemical polishing of steel surfaces stainless.
• hydroxybenzoic acid plays the role brightening agent.
• Hydroxybenzoic acid can be unsubstituted such as salicylic or substituted acid such as 5-sulfosalicylic acid or acid aminosalicylic acid.
• Salicylic acid and 5-sulfosalicylic acid are preferred.
• the cationic surfactant comprises advantageously a quaternary ammonium salt.
• Quaternary ammonium salt is preferably selected from those which include at least one alkyl radical with long chain, linear or branched. If necessary, we prefer select the quaternary ammonium salt from those in which the long chain alkyl group contains at least 8 carbon atoms, of preferably at least 10 carbon atoms, such as lauryl groups, cetyl and stearyl, for example.
• at least one other alkyl radical, linear or branched, or a radical benzyl, substituted or unsubstituted may be present.
• Examples are the salts cetyldimethylbenzylammonium, distearyldimethylammonium, lauryldimethylbenzylammonium and lauryltrimethylammonium.
• Ammonium salts specially recommended quaternary belong to the class formed of salts water-soluble alkylpyridinium, especially cetylpyridinium and laurylpyridinium.
• Quaternary ammonium salts comprising a long-lasting alkyl radical chain as defined above, are preferably selected from halides, especially among chlorides.
• the alkylpyridinium chlorides are particularly preferred, in particular laurylpyridinium chloride. Salts of quaternary ammonium which can be used in the baths according to the invention are accessible among DEHYQUART® (HENKEL) brand products.
• HENKEL DEHYQUART®
• the ferricyanide complex ions are complex cyanides of general formula [Fe III (CN) 6 ] 3- , also called hexacyanoferrates (III). They can be present in the aqueous solution in the form of all dissolved compounds such as, for example, hexacyanoferric acid (III), ammonium ferricyanide and ferricyanides of alkali and alkaline earth metals. Preferred compounds are the alkali metal ferricyanides, potassium ferricyanide being especially preferred.
• the contents respective hydrochloric, nitric and hydroxybenzoic acids, surfactant cationic and ferricyanide complex ions are chosen depending on the grade of stainless steel subject to polishing as well as conditions of polishing, in particular of the profile of the steel object subjected to polishing, of its volume, volume of the bath, its temperature and the agitation at which it is possibly submits. They must therefore be determined in each case particularly through routine laboratory testing.
• the hydrochloric acid content of the aqueous solution is at least equal to 1, preferably 2, moles per liter and it generally does not exceed 6, preferably 5, moles per liter.
• Content nitric acid is at least 0.001, preferably 0.005, mole per liter of the aqueous solution and it does not generally exceed 0.3, preferably 0.03, moles per liter of the aqueous solution.
• the hydroxybenzoic acid content is at least 0.1, preferably 1, mg per liter of the aqueous solution and it generally does not exceed 15,000, preferably 7,000 mg per liter of the solution aqueous.
• the content of cationic surfactant is at least 0.1, preferably 1, mg per liter of aqueous solution and it does not generally exceed 1000, of preferably 100 mg per liter of aqueous solution.
• the content of ferricyanide complex ions is at least equal to 1 ⁇ 10 -5 mole per liter. Very particularly preferred is a content at least equal to 3 ⁇ 10 -5 moles per liter.
• the content of ferricyanide complex ions does not exceed 1 mole per liter and in a particularly preferred manner, the content of ferricyanide complex ions does not exceed 1 x 10 -3 mole per liter. Particularly preferred is a content which does not exceed 3 x 10 -4 moles per liter.
• these contain, in the aqueous solution, an additive capable of decomposing nitrous acid.
• the function of this additive is to decompose at least part of the nitrous acid which forms during the polishing of a steel surface, as a consequence of oxidation of ferrous ions released in the bath during polishing.
• the additive capable of breaking down nitrous acid is preferably selected from urea and its derivatives, such as thiourea and ureines.
• the optimum content of additive capable of breaking down nitrous acid is 0.01 to 5 g per liter of the aqueous solution.
• the baths in accordance with this embodiment of the invention are specially adapted for polishing treatments in which the ratio between the surface in contact with the bath and the volume thereof is greater than 10 m -1 .
• the baths according to the invention may optionally contain additives usually present in chemical metal polishing baths, for example example of surfactants other than the defined cationic surfactant above, alcohols and viscosity regulators.
• additives usually present in chemical metal polishing baths for example example of surfactants other than the defined cationic surfactant above, alcohols and viscosity regulators.
• the baths according to the invention may also contain other acids minerals commonly found in chemical polishing baths, for example example of sulfuric acid. However, they are essentially free of acid phosphoric and phosphate ions.
• the baths according to the invention are suitable for the chemical polishing of stainless steel surfaces. They are well suited for polishing steels austenitics containing between 16 and 26% by weight of chromium and between 6 and 22% by weight of nickel, such as steels in grades 18/8 and 18/10. Baths according to the invention are especially well suited for polishing austenitic steels containing molybdenum. Austenitic steels, with or without molybdenum, are typically AISI-304, 304L, 316, 316L, 904 and 904L steels. Baths according to the invention has the distinction of carrying out the polishing of such steels at high speed slow. They can be used at all temperatures below the temperature of the bath.
• the baths according to the invention have the particularity of allowing slow polishing, which makes them suitable for polishing large industrial devices.
• the baths according to the invention have the additional advantage of performing good quality polishes welded joints according to the rules of art.
• the invention therefore also relates to a method for polishing a stainless steel surface, where you put the surface in contact with a chemical polishing bath according to the invention.
• bringing the metal surface with the bath can be carried out in any suitable manner, by example by immersion.
• the contact time of the surface to be polished with the bath must be sufficient to achieve effective surface polishing. He can not however not exceed a critical value beyond which the bath loses its polishing properties. The optimum contact time depends on many parameters such as the grade of steel, the configuration and the initial roughness of the surface to be polished, the composition of the bath, the working temperature, the agitation of the bath in contact with the surface, the ratio between the area of the surface to be polished and the bath volume; it must be determined in each particular case by work routine in the laboratory.
• the contact time of the surface to be polished with the bath is generally at least 1 hour, preferably at least 2 hours. In general, contact time does not exceed 24 hours, preferably not 12 hours.
• the setting temperature work of the bath is, in general, lower than its boiling point.
• the processing temperature is less than 80 ° C. Good results are obtained at a temperature less than or equal to 70 ° C.
• Temperature of implementation of the bath is, in general, at least equal to the temperature ambient. Preferably, the temperature is at least 35 ° C.
• the bath is operated at normal atmospheric pressure at a temperature of 35 at 70 ° C, and the surface to be polished is kept in contact with the bath for a time between 2 and 12 hours.
• the bath used is therefore different from the bath of Example 1 by the absence of potassium ferricyanide.
• Example 1 A comparison of the results obtained in Example 1 (in accordance with the invention) with those obtained in Example 3 (not in accordance with the invention) made appear the progress brought by the invention, as regards roughness and the shine obtained after polishing.

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

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• 1994
  • 1994-03-28 FR FR9403732A patent/FR2717829B1/fr not_active Expired - Fee Related
• 1995
  • 1995-03-11 TW TW084102328A patent/TW311942B/zh active
  • 1995-03-13 CA CA002186401A patent/CA2186401A1/fr not_active Abandoned
  • 1995-03-13 US US08/702,435 patent/US5762819A/en not_active Expired - Fee Related
  • 1995-03-13 DE DE69524072T patent/DE69524072T2/de not_active Expired - Fee Related
  • 1995-03-13 CZ CZ962857A patent/CZ285932B6/cs not_active IP Right Cessation
  • 1995-03-13 ES ES95913105T patent/ES2168360T3/es not_active Expired - Lifetime
  • 1995-03-13 PL PL95316536A patent/PL316536A1/xx unknown
  • 1995-03-13 ZA ZA952067A patent/ZA952067B/xx unknown
  • 1995-03-13 HU HU9602669A patent/HU214367B/hu not_active IP Right Cessation
  • 1995-03-13 SK SK1282-96A patent/SK281732B6/sk unknown
  • 1995-03-13 CN CN95193129A patent/CN1044264C/zh not_active Expired - Fee Related
  • 1995-03-13 JP JP7524929A patent/JPH10500732A/ja active Pending
  • 1995-03-13 BR BR9507264A patent/BR9507264A/pt not_active Application Discontinuation
  • 1995-03-13 UA UA96093741A patent/UA48129C2/uk unknown
  • 1995-03-13 AU AU20702/95A patent/AU2070295A/en not_active Abandoned
  • 1995-03-13 PT PT95913105T patent/PT753083E/pt unknown
  • 1995-03-13 WO PCT/EP1995/000942 patent/WO1995026428A1/fr active IP Right Grant
  • 1995-03-13 EP EP95913105A patent/EP0753083B1/fr not_active Expired - Lifetime
  • 1995-03-13 IL IL11296695A patent/IL112966A0/xx not_active IP Right Cessation
  • 1995-03-27 YU YU19895A patent/YU48903B/sh unknown
  • 1995-03-28 HR HR950163A patent/HRP950163B1/xx not_active IP Right Cessation
• 1996
  • 1996-03-13 RU RU96119757A patent/RU2124577C1/ru active
  • 1996-09-24 BG BG100865A patent/BG62338B1/bg unknown
  • 1996-09-27 NO NO964114A patent/NO964114L/no not_active Application Discontinuation
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