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
  • C23C22/78—Pretreatment of the material to be coated
• • 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
  • C23C22/78—Pretreatment of the material to be coated
  • C23C22/80—Pretreatment of the material to be coated with solutions containing titanium or zirconium compounds

Definitions

• the invention relates to an improved method for cleaning, degreasing and activating metal surfaces, in particular surfaces made of iron and steel and corresponding composite parts with aluminum and zinc, before a subsequent treatment thereof for the layer-forming phosphating.
• Such cleaning solutions usually contain surface-active substances, such as wetting agents and emulsifiers, and so-called builder juices, for example sodium hydroxide, alkali, to strengthen the emulsifying, saponifying and dirt-carrying capacity metal carbonates, alkali metal orthophosphates, corresponding condensed phosphates, such as sodium pyrophosphate or sodium triphosphate, and optionally also silicates and borates.
• surface-active substances such as wetting agents and emulsifiers, and so-called builder juices, for example sodium hydroxide, alkali, to strengthen the emulsifying, saponifying and dirt-carrying capacity metal carbonates, alkali metal orthophosphates, corresponding condensed phosphates, such as sodium pyrophosphate or sodium triphosphate, and optionally also silicates and borates.
• builder juices for example sodium hydroxide, alkali
• condensation phosphates such as sodium pyrophosphate or sodium triphosphate
• a characteristic feature of such solutions is their content of those builder substances which require free alkalinity in aqueous solution - that is to say whose alkalinity exceeds that of secondary orthophosphate. and a content of condensed phosphates.
• the pH of these cleaning solutions is in the range from 8.5 to 11.5.
• the cleaners described above have a number of serious disadvantages.
• the material to be treated usually passes through a rinsing zone following the cleaning zone and is then introduced into the phosphating zone.
• the material first comes into contact with the so-called pre-spray from the first spray ring in the phosphating zone.
• the rinsing water solution adhering to the metal surface - still contaminated with an alkaline cleaning solution - is washed off by the phosphating solution, while at the same time the formation of the phosphate layer begins.
• the object of the present invention is therefore a method for pretreating metal surfaces to be developed before phosphating, in which the disadvantages of the cleaning solution described above, which have a negative effect on the subsequent phosphating, are avoided.
• the cleaning and degreasing process characterized above can be used to achieve excellent cleaning effects with regard to the metal surfaces to be treated as well as perfect phosphating layers in the subsequent phosphating. Due to the choice of the low pH range according to the invention of the cleaners, their total together with reduced free alkalinity and the lowest possible amount of condensed phosphates, the difficulties which have been observed up to now in layer-forming phosphating can be avoided without the quality of the desired cleaning success suffering.
• the surfaces are treated with solutions which have a pH in the range from 6.5 to 8.0.
• the cleaning solutions to be used in the process according to the invention contain as builder components mainly alkali metal or ammonium salts of the primary and / or secondary orthophosphate, the content of primary or secondary phosphate primarily depending on the pH of the cleaning solution - within the scope of above limits - depends.
• Alkali metal borates such as disodium tetraborate, and / or alkali metal bicarbonates, for example sodium bicarbonate, are particularly suitable as further builder substances for the cleaning solutions - which require an improved cleaning action thereof. Accordingly, the metal surfaces are treated according to the invention with solutions which contain alkali metal borates and / or - at pH values of the solutions in the range from 7 to 8 - alkali metal hydrogen carbonates.
• the latter carbonates are expediently only used in neutral or weakly alkaline solutions, since acidic cleaning solutions would cause these active ingredients to decompose.
• Condensed phosphates for example tetrasodium pyrophosphate and / or pentasodium triphosphate, are used as builder substances according to the invention only to the extent that they are required to compensate for the water hardness of the process water used to prepare the cleaning solution.
• the cleaning solutions used to treat the metal surfaces do not contain any condensed phosphates.
• hydroxypolycarboxylic acids such as citric acid
• aminopolycarboxylic acids such as nitrilotriacetic acid or ethylenediaminetetraacetic acid
• phosphonic acids such as ethane-1-hydroxy-1,1-diphosphonic acid or aminotrimethylenephosphonic acid
• the metal surfaces are treated with cleaning solutions which contain other compounds complexing calcium ions.
• Further constituents of the cleaning solutions to be used according to the invention are customary anionic, cationic or nonionic wetting agents and emulsifiers.
• the nonionic types slaughter.jedoch preferably used, for example, addition products of ethylene oxide with fatty alcohols, alkylphenols, fatty amines or polyoxypropylene ylenglykole p.
• the layer refiners and activators for example titanium phosphates, which are customary and known for this purpose, can also be added to the cleaning solutions.
• Such an activating agent is described in DE-AS 20 38 105, which can also preferably be used in the sense of the method according to the invention.
• This activating agent consists essentially of titanium salt, disodium orthophosphate and gelatin or alkali metal or ammonium salts of polyuronic acids.
• the cleaning solutions contain the usual components mentioned in the usual concentrations.
• the use of the cleaning solutions described above in the process according to the invention is generally carried out in the manner known and customary for cleaning and degreasing processes.
• the temperature of the cleaning solution is usually in the range of about 40 to 70 ° C.
• the metal surfaces for which the method according to the invention can preferably be used include, in particular, those made of iron and steel and also composite parts of iron and steel with aluminum and / or zinc, as are often used, for example, in automobile body construction.
• the metal surfaces are generally rinsed after cleaning and then subjected to a layer-forming phosphating process - likewise in a known manner.
• Oiled iron sheet strips of deep-drawing grade ST 1405 were treated for 2 minutes under 1.5 bar spray pressure with a cleaning solution which had a temperature of 60 ° C. and contained 2.5 g / l of a cleaning agent mixture of the following composition: The pH of the cleaning solution was 7.4.
• the cleaned and degreased iron sheet strips were rinsed with a rinse water which contained 0.07 g / 1 of the detergent mixture, corresponding to 3 l / m 2 of fresh water supply, and then moved into the phosphating zone at a throughput rate of 1 meter / minute.
• the iron sheet strips were phosphated by spraying on a phosphating solution for 3 minutes at a spray pressure of 0.8 bar and a bath temperature of 65 ° C., the solution containing 3 percent by weight of a concentrate of the following composition:
• the ratio of total acid to free acid in the phosphating solution was adjusted to a value of 10 by adding dilute sodium hydroxide solution and furthermore a nitrite concentration of 0.015% by weight was added maintenance of sodium nitrite.
• the sheets were then rinsed thoroughly with deionized water, dried and then an optical assessment of the phosphating layer formed was carried out.
• the formation of the layer turned out to be perfectly good; that is, the layer was closed and even.
• Example 1 the procedure in the following examples was analogous to that in Example 1. These examples differ from Example 1 in the composition of the cleaning solution used and - as the attached comparative examples show - possibly in the formation of the phosphating layer.
• composition of the detergent mixture pH value of the cleaning solution: 7.8 Formation of the phosphating layer: perfect; extraordinarily even, closed and hard.
• composition of the detergent mixture pH value of the cleaning solution: 6.7
• composition of the detergent mixture pH value of the cleaning solution: 6.5 Formation of the phosphating layer: perfect; . extraordinarily even, closed and hard.
• composition of the detergent mixture pH value of the cleaning solution: 9.0
• Formation of the phosphating layer inhomogeneous, torn open in an island shape, partly blue passivation layers (iron phosphate).
• composition of the detergent mixture pH value of the cleaning solution: 11.0 Formation of the phosphating layer: completely uneven and streaky, strong appearance of blue passivation layers (iron phosphate).

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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)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Detergent Compositions (AREA)
• Chemical Treatment Of Metals (AREA)

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• 1979
  • 1979-12-21 DE DE19792951600 patent/DE2951600A1/de not_active Withdrawn
• 1980
  • 1980-12-12 DE DE8080107866T patent/DE3065089D1/de not_active Expired
  • 1980-12-12 EP EP80107866A patent/EP0031103B1/fr not_active Expired
  • 1980-12-18 JP JP17815180A patent/JPS5693880A/ja active Granted
  • 1980-12-18 BR BR8008327A patent/BR8008327A/pt unknown
  • 1980-12-19 AT AT0620980A patent/AT372116B/de not_active IP Right Cessation
  • 1980-12-19 CA CA000367202A patent/CA1151497A/fr not_active Expired
  • 1980-12-22 US US06/219,245 patent/US4384900A/en not_active Expired - Fee Related

Patent Citations (6)

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