Abstract: A process of producing a phosphate coating on a metal surface of iron or steel by contacting the surface with an aqueous phosphating solution on the basis of magnesium phosphate. The solution contains 0.2 to 4 g/l magnesium, 1 to 20 g/l phosphate (calculated as P.sub.2 O.sub.5) and a peroxide compound as an accelerator. The phosphating solution is free of inorganic substances which are not precipitable with calcium hydroxide in a neutral or alkaline medium. It is preferred to use phosphating solutions which also contain activators, which are precipitable with calcium hydroxide in a neutral or alkaline medium.

Abstract: 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.

Abstract: 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 comprising0.4 to 30 g/l Zn4 to 30 g/l P.sub.2 O.sub.55 to 50 g/l NO.sub.3up to 10 g/l Fe(II) ; andup to 0.3 g/l (Fe(III)wherein the weight ratio of free P.sub.2 O.sub.5 to total P.sub.2 O.sub.5 is (0.04 to 0.50):1 and, replenishing said phosphating solution with Zn, NO.sub.3 and P.sub.2 O.sub.5 in a weight ratio ofZn:NO.sub. 3 P.sub.2 O.sub.5 =(0.60 to 0.30):(0.2 to 0.4):1.wherein the Fe(II) content is adjusted by oxidation with nitrate or nitrite derived from nitrate optionally employed with an oxygen-containing gas, H.sub.2 O.sub.

Abstract: A method of determining the weight per unit of area of conversion layers, particularly of phosphate layers, on metals, in which the heat radiated from the dry surface which is covered with the conversion layer and is at the temperature T and the heat radiated from a reference surface or a reference cavity which is at the temperature T+t are periodically measured at a temperature between 15.degree. and 50.degree. C. by a wavelength-insensitive electic infrared detector. t is preferably selected in the range from +15.degree. to +3.degree. C. from -15.degree. to -3.degree. C. above or below T. The weight of the conversion layer per unit of area is determined from the amplitude of the resulting electric alternating signal. The radiant heat is suitable measured by an infrared detector having a sensor which consists of a pyroelectric sheet of polyvinylidene fluoride.

Abstract: During a method of phosphating a metal surface which includes at least in part iron or steel and is dipped into or flooded with a phosphating solution which contains layer-forming cations and nitrate or equivalent accelerators, the iron content is limited by a precipitation of iron phosphate. A partial volume of the phosphating solution is intermittently withdrawn from the bath tank and in a separate aerator is contacted with oxygen or an oxygen-containing gas. The iron phosphate sludge is removed from the resulting solution, which is then returned to the bath tank. The partial volume of the phosphating solution is supplied from below into and is aerated in an aerator, which is provided with an aspirating aerating agitator and which is tapered at least in its lower portion. When the aerator has been terminated, the phosphating solution which has been depleted of iron(II) is sucked off upwardly and is returned to the bath tank.

Abstract: 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.

Abstract: Disclosed is a process of producing a phosphate coating on a composite part consisting of steel and galvanized steel, which comprises alkaline cleaning, rinsing with an aqueous rinsing bath, and phosphatizing with an aqueous zinc phosphate solution. The formation of a non-uniform coating and of spots is avoided in the process of the invention by the use of a rinsing bath which contains at least 0.2 g/l alkali borate, at least 0.1 g/l alkali silicate and at least 0.05 g/l alkali nitrite, and which preferably contains said components in a total up to 5 g/l.If the composite part is to be activated with an activating bath which contains titanium phosphate before being contacted with the zinc phosphate solution, the activating bath must contain at least 1 g/l and preferably up to 4 g/l of tetraalkalipyrophosphate.The process of the invention can be used to prepare composite parts of steel and galvanized steel for subsequent painting, particularly by electrophoretic dip painting.

Abstract: Disclosed is a process of producing phosphate coatings on surfaces which consist of aluminum or its alloys and of at least one of the materials steel and galcanized steel by spraying or by spraying and dipping. Uniform phosphate layers having a high cover factor are obtained by the use of a phosphating solution which contains about 0.4 to about 0.8 g/l Zn, about 10 to about 20 g/l P.sub.2 O.sub.5, at least one accelerator and about 80 to about 220 mg/l fluoride ("F(el)"), as determined by a fluoride-sensitive electrode immersed into the bath solution and in which the content of free acid (FA) (in points) has been adjusted to and is maintained at a value corresponding to FA=(0.5 to 1.0)+K wherein K is calculated as K=(0.002 to 0.012).times.F(el). The free acid (FA) content is preferably adjusted to and maintained at FA=(0.04 to 0.06).times.C.sub.P.sbsb.2.sub.O.sbsb.5 +K and the content of free acid (FA) is determined using K=(0.003 to 0.009).times.F(el).

Abstract: In a process for maintaining a given zinc content in nickel-containing zinc phosphate baths,(a) nickel is precipitated in a bath sample by addition of dimethylglyoxime, a soluble copper complex compound is added and the liquid is then titrated against a copper-sensitive electrode, for determining the zinc content, with a volumetric solution containing a complexing agent for zinc and copper;(b) the automatic metering of zinc-containing supplementary concentrate is then regulated on the basis of the deviation, ascertained in this way, from the given zinc content (prescribed value).

Abstract: A process for the phosphatizing of metals, particularly iron, steel and zinc, in which the metal is contacted with acidic aqueous zinc phosphate solutions, containing an oxidizing agent, which containfrom 0.4 to 1.5 g/liter of Zn,from 0 to 1.3 g/liter of Ni andfrom 10 to 26 g/liter of P.sub.2 O.sub.5,and in which the weight ratio of Zn to P.sub.2 O.sub.5 is adjusted to a value of (from 0.012 to 0.12):1 and of Ni to Zn to a value of (from 0 to 1.5):1, and the bath is supplemented with a concentrate, in which Zn, Ni and P.sub.2 O.sub.5 are present in a weight ratio of (from 0.18 to 0.33:(from 0 to 0.06):1, so as to obtain satisfactory phosphatizing results over a long period.Preferably, the zinc phosphatizing solutions, which, in addition, may also contain simple or complex fluorides and compounds that reduce the weight of the coat, are applied at a temperature within the range of from 30.degree. to 65.degree. C.

Abstract: A composition for the phosphatizing of metals, particularly iron and steel, which comprises an aqueous acidic, chlorate-containing zinc phosphate solution which containsfrom 0.5 to 1.5 g/liter Znfrom 0.4 to 1.3 g/liter Nifrom 10 to 26 g/liter P.sub.2 O.sub.5from 0.8 to 5 g/liter Cl0.sub.3and in which no nitrite is added, and in which the weight ratio ofZn to Ni shall be adjusted to a value of 1: (from 0.5 to 1.5), that of Zn to P.sub.2 O.sub.5 to a value of 1: (from 8 to 85) and that of free P.sub.2 O.sub.5 to a value of from (0.005 (at about 30 degrees C.) to 0.06 (at about 60 degrees C.)): 1.The composition is particularly useful in processes for the preparation of metal surfaces for electrophoretic coating, particularly for cathodic immersion coating.