Metallgesellschaft Aktiengesellschaft

Dynamit Nobel Aktiengesellscha

Horst Gehmecker

Thomas Kolberg

Werner Rausch

Dieter Hauffe

Peter Schubach

Gerhard Muller

Hardy Wietzoreck

Thomas Wendel

Joachim Heitbaum

Peter Jorns

Georg Blumlhuber

Heinz Dosch

Dirk Meyer

Thomas Nitschke

Rudiger Rein

Lothar Kaul

Process of phosphatizing metal surfaces

The invention is in a composition and process for the chromium free passivating postrinsing of conversion layers on metals before the application of a paint or adhesive. The conversion layers can be on the bases of phosphate layers, at least two polyvalent metal ions with complex formers, titanium, zirconium and/or hafnium. The postrinsing agent is an aqueous solution which has been adjusted to a pH value of up to 5 and which contains an aluminum fluorozirconate having an Al:Zr:F mole ratio of (0.15 to 8.0):1:(5 to 52), and in which solutions the total concentration of Al+Zr+F is 0.1 to 8.0 g/l. The postrinsing solutions may additionally contain at least one of the anions benzoate, caprylate, ethyl hexoate, salicylate in a total concentration of 0.05 to 0.5 g/1 and may preferably be adjusted to the required pH value with cations of volatile bases, such as ammonium, ethanolammonium and di- and triethanolammonium. The paint is subsequently applied suitably by cathodic electrocoating or powder coating or from a low-solvent high-solids paint. The rinsing treatment is over a period of 1 to 120 seconds at temperatures of 20.degree. to 80.degree. C. The invention is used as a pretreatment to the application of a paint coating, film coating or adhesive coating.

Process for a passivating postrinsing of conversion layers

In a process of phosphating metal surfaces phosphating solutions are employed which are substantially free of nickel and contain

Process for phosphating metal surfaces

A process for forming phosphate coatings on metal surfaces is provided which comprises the steps of contacting said metal surface with an Fe(II)-containing phosphating solution comprising

Process of forming phosphate coatings on metal surfaces

For phosphating metal surfaces which consist at least in part of aluminum, by means of phosphating solutions which contain zinc, phosphate and fluoride, any titanium which has entered the phosphating solution and would disturb the formation of the layer is precipitated by an addition of SiO-containing compounds and after the precipitate has been removed, the content of free fluoride is readjusted to the required concentration. Particularly suitable compounds which contain SiO, consist of alkali metasilicate, alkali orthosilicate and/or alkali disilicate, preferably used in an amount of 0.05 to 1 g/l of the phosphating solution, or of silica, which is preferably used in an amount of 0.5 to 10 g per liter of the phosphating solution (calc. as Si).

Phosphating process

In a process of removing complexly bound titanium and/or zirconium from acid aqueous solutions the solution which contains the complexly bound titanium and/or zirconium is conditioned in that its pH value is raised to at least 8, any precipitate thus formed is removed and the solution thus treated is passed through an ion exchange plant comprising a cation exchange material and an anion exchange material. The solution is preferably passed through an ion exchange plant which contains the cation exchange material in the H.sup.+ form and the anion exchange material in the OH.sup.- form. The process is particularly intended for the treatment of solutions obtained by the chemical treatment of surfaces preferably of metals, which solutions contain titanium and/or zirconium in the form of fluoro complexes.

Process for removing titanium and zirconium from aqueous solutions

A process to form phosphate coatings on individual parts of metal which at least on part of their surface consists of iron or steel. The individual parts are contacted at a temperature in the range of from 60 to 100 degrees centigrade for 3 to 30 seconds with an aqueous phosphating solution which contains 10 to 80 g/l zinc, 12 to 80 g/l phosphate (calculated as P.sub.2 O.sub.5), 40 to 150 g/l nitrate and, in addition 0.1 to 10 g/l fluoride, 0.01 to 10 g/l nickel, 0.0001 to 0.1 g/l copper, and may also contain tartaric acid, citric acid and/or manganese and in which the ratio of free acid to total acid has been adjusted to (0.1 to 0.3):1 and which contains at least 80 points of total acid and is virtually free of iron(II) ions. Prior to phosphating treatment, the individual parts may be cleaned and may optionally be treated to remove rust, scale and phosphate layers and/or be activated. After the phosphating treatment they may be passivated with an after-rinse solution. Each of said process steps is carried out for 3 to 30 seconds.

Process of forming phosphate coatings on metals

Described is a process for determining the zinc content of an acid aqueous phosphating bath. A bath sample is titrated at a pH value between 1.2 and 1.7 in the presence of ethylenediaminetetraacetic acid, hexamethylenetetramine and alkalihexacyanoferrate (III) with an alkalihexacyanoferrate(II) until the potential at an oxidation-reduction electrode immersed into the bath sample reaches an inflection point. Any content of nitrite and/or iron(II) ions must be removed by an addition of nitrite-destroying substances and by an oxidation to iron(III) ions at a pH value above 8. The process is particularly suitable for determining the zinc concentration of phosphating baths which contain 0.4 to 2.0 g/l Zn. The presence in phosphating baths of additional cations such as manganese and/or calcium and/or nickel and/or magnesium does not interfere with the process. The analysis can be automatic and may directly be used to control a metering device for supplying make-up concentrates to the phosphating bath.

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Hofheim, Germany

Horst Gehmecker