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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/02—Apparatus characterised by being constructed of material selected for its chemically-resistant properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/16—Preventing evaporation or oxidation of non-metallic liquids by applying a floating layer, e.g. of microballoons
• • 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
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/02—Apparatus characterised by their chemically-resistant properties
  • B01J2219/0204—Apparatus characterised by their chemically-resistant properties comprising coatings on the surfaces in direct contact with the reactive components
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/02—Apparatus characterised by their chemically-resistant properties
  • B01J2219/025—Apparatus characterised by their chemically-resistant properties characterised by the construction materials of the reactor vessel proper
  • B01J2219/0277—Metal based

Definitions

• the substance may be, for example, a high boiling point parafiin such as liquid paraffin, petroleum jelly, a paraffin wax, an animal or vegetable oilmolin, tallow or castor oil, bitumen, a low molecular weight synthetic resin, or a low melting point natural resin.
• a high boiling point parafiin such as liquid paraffin, petroleum jelly, a paraffin wax, an animal or vegetable oilmolin, tallow or castor oil, bitumen, a low molecular weight synthetic resin, or a low melting point natural resin.
• the layer-forming substance must be inert, i.e. stable at the temperature of the bath against attack by the solution in the bath, by any hydrogen generated, or by atmospheric oxygen. It must, of course, also be less dense than the acidic solution. It is preferable that it contains very little or no material volatile at the temperature of operation of the bath and it should be of such viscosity at the operating temperature of the bath that the layer will readily reform after being broken by, for example, the entry or exit of articles to the bath, or the exit of bubbles of gas or vapour.
• the preferred layer-forming substances are, at the temperature of operation of the bath, liquid hydrocarbon materials such as various grades of oils, the viscosity being dependent largely on the operating temperature of the bath. It has been found that when pickled articles are withdrawn from the pickling bath through a layer of such liquid hydrocarbon material the hydrocarbon shows little tendency to cling to the article and is readily washed off. Of the liquid hydrocarbon materials those which are chemically saturated (i.e. contain no unsaturated carbon to carbon bonds) are preferred due to their high degree of stability.
• the inert surface layer is effective in substantially reducing evolution of acid fumes from the bath.
• the following table shows the time required to decolourise a piece of alkaline phenol phthalein paper placed above a solution of 20% HCl at 95 C. covered to various depths with layers of a hydrocarbon oil having a viscosity of 8 Patented June 6, 1961 centipoises at 95 C. A piece of the same paper was decolourised in 5 minutes by a normal atmosphere:
• the layer of substance should be at least 10 mm. thick.
• the depth of the layer can be varied between fairly wide limits, these limits being dependent on the viscosity range of the materials used, the temperature of operation of the bath and the amount of foam formed at the interface between the inert substance and the aqueous acid.
• the viscosity of the layer substance at the operating temperature can vary widely but it should preferably not exceed 100 poises. To ensure rapid removal of the layer forming substance from the metal article and to reduce drag out of the substance to a minimum the viscosity of the substance at the temperature of operation of the bath may be as low as 0.5-2 centipoises.
• a surprising feature of the invention is that the tendency of the surface layer to cling to articles entering the bath does not seriously affect the speed at which the acid reacts with the metal. in any case this tendency may be minimised by using a layer of a substance with a low viscosity at the temperature of operation. Removal of adherent surface layer from the articles being treated may also be assisted by the addition of surface active agents to the acid solution. It is preferred that the surface tension of the acid solution be reduced in this way to less than 40 dynes/cm., but the quantity of surface active agent added should be less than that required to disperse or emulsify the surface layer into the acid solution.
• the inert layers of the present invention are so effective in reducing fuming from hot acid baths it is desirable to colour them, for example by adding a red dye, in order to warn operators that the baths are, in fact, hot.
• Example I In the pickling treatment of rusty iron in 20% hydrochloric acid solution (200 gm. HCl gas/litre) in water at 90 C., a process which normally has to be carried out at a maximum temperature of 35 C., the loss of acid from a bath without surface layer was found to be 1550 gm./ sq. metre/hour.
• the bath was then covered with a 6 mm. thick layer of a hydrocarbon material having a viscosity of 3.5 centipoises at 90 C. and a flash point of 155 C.
• the loss of acid was less than 10 gm./sq. metre/hour.
• the pickling treatment was carried out in a 5 litre glass beaker lightly lagged with asbestos string. 308 watts of electricity were required to maintain a steady temperature of 90 C. without a surface layer. With the surface layer only 89 watts of electricity were required to maintain 90 C.
• Example II A bath was made up to the following composition:
• Non-ionic surface active agent 1 Water Remainder
• the surface active agent was an anhydrous condensation p wam rmm WW slightly soluble in the inert layer escri e ow, and reduced the surface tension of the bath to 36 dynes/cm.
• This bath was covered with a layer of saturated hydrocarbon material 12 mm. thick and operated at 24 C.
• the hydrocarbon material was an oil having a viscosity of 5.5 centipoises at the operating temperature and had a flash point of 125 C.
• Titanium panels were treated in this bath for minutes followed by rinsing in water and drying. All scale had been removed without noticeable evolution of acid spray or fumes from the surface of the bath, though the passage of small quantities of gaseous nitrogen oxides through the layer was, of course, not prevented.
• Example III A bath was made up to the following composition:
• the surface active agent was an akyl trimethyl, ammonium salt which reduced the surface tension of the bath to 30 dynes/cm.
• This bath was covered with an inert layer as in Exam- 70 ple II and heated to 60 C.
• Stainless steel wire was treated in this bath for 5 minutes followed by rinsing in water and drying. All scale had been removed without noticeable evolution of spray or fumes from the surface of the bath.
• Example IV A bath was made up to the following composition:
• S.G. 1.84 Percent by weight Sulphuric acid (S.G. 1.84) 15.0 Inhibitor 0.005 Anionic surface active agent 0.1 Oil soluble red dye 0.01 Water Remainder
• the surface active agent was a secondary alkyl sulphate which reduced the surface tension of the bath to 33 dynes/cm.
• the inhibitor was based on di-ortho tolyl thio urea.
• This bath was covered with a layer of hydrocarbon material 12 mm. thick and heated to 65 C.
• the bydrocarbon material had a viscosity of 5.5 centipoises at the operating temperature and a flash point of 155 C.
• Scaly steel panels were treated in this bath for 30 minutes followed by rinsing in water and drying. All scale had been removed without noticeable evolution of spray or fume. The trace of hydrocarbon material carried over on the panels was removed without difliculty in the water rinse.
• Example V A bath was made up to the following composition:
• S.G. 1.84 Percent by weight Sulphuric acid (S.G. 1.84) 10.0 Inhibitor 0.005 Water Remainder The inhibitor was based on di-ortho tolyl thio urea.
• a layer of castor oil (S.G. 0.962-0.966 at 15 C., viscosity 700 centipoises at 25 C.) 12 mm. thick was poured over the bath.
• Rusty iron bolts were treated in this bath at 70 C. for 30 minutes. The bolts were withdrawn from the bath through the oil layer and rinsed. After rinsing they still showed water break and the oil layer remaining was satisfactory at a temporary protective coating for the rust free bolts.
• a process of pickling metal which comprises providing an acid pickling solution, covering all of the surface of said solution with a non-aqueous surface layer of inert liquid which is substantially immiscible with said pickling solution and substantially nonvolatile and stable at the operating temperature of said solution, including in said surface layer and said pickling solution a surface active agent which is soluble in both said layer and said pickling solution, thereafter passing the metal to be pickled through said surface layer and into said solution, withdrawing the thus pickled metal through said surface layer, and then rinsing said metal with water whereby the surface active agent in said surface layer facilitates the removal of any adherent surface layer.
• a process of pickling metal which comprises providing an acid pickling solution, covering all of the surface of said solution with a non-aqueous surface layer of saturated hydrocarbon which is liquid at the temperature of said solution and substantially immiscible therewith, said liquid being stable and substantially non-volatile at the operating temperature of said solution and inert with respect to the constituents of said solution, said surface layer having a viscosity of from 2-10 centipoises and a minimum thickness of at least mm., including in said surface layer and said solution a surface active agent which is soluble in both said layer and solution, the amount of surface active agent dissolved in the solution being sufficient to lower the surface tension to less than dynes/cm., said surface active agent having suflicient solubility in said surface layer to take up any surface active agent separated out from said pickling solution, thereafter passing the metal to be pickled through said surface layer and into said solution, withdrawing the thus pickled metal through said surface layer, and then rinsing said metal with water whereby the surface active agent in said surface

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Chemical Treatment Of Metals (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=26238166

Family Applications (2)

Family Applications After (1)

Country Status (7)

Cited By (6)

Families Citing this family (14)

Citations (7)

Family Cites Families (17)

• 0
  • NL NL220946D patent/NL220946A/xx unknown
  • NL NL107385D patent/NL107385C/xx active
  • BE BE561107D patent/BE561107A/xx unknown
• 1956
  • 1956-09-25 GB GB29265/56A patent/GB865210A/en not_active Expired
• 1957
  • 1957-09-16 US US683975A patent/US2987425A/en not_active Expired - Lifetime
  • 1957-09-18 ES ES0237642A patent/ES237642A1/es not_active Expired
  • 1957-09-24 DE DEI13762A patent/DE1169759B/de active Pending
  • 1957-09-25 CH CH5094357A patent/CH366188A/de unknown
• 1958
  • 1958-01-27 US US711135A patent/US2987427A/en not_active Expired - Lifetime
  • 1958-01-30 DE DEJ14346A patent/DE1165378B/de active Pending

Patent Citations (7)

Also Published As

Similar Documents