DE2038105B2 - PROCESS FOR PRE-TREATMENT OF SURFACES MADE OF IRON, STEEL AND HOT GALVANIZED MATERIAL FOR THE APPLICATION OF ZINC PHOSPHATE LAYERS - Google Patents

Description

According to the invention, disodium phosphate is generally used as sodium phosphate. However, disodium phosphate may be wholly or partly replaced by other sodium phosphates "such as monosodium orthophosphate, Trinutriumorthophosphat, tetrasodium pyrophosphate and sodium tripolyphosphate are replaced. These phosphates individually come or in a mixture for use, and its quantity is dimensioned such that the same concentration of P ₂ O ₅ , which is required for disodium phosphate.

The lithium-containing compound and sodium phosphate are used in proportions such as that the titanium content is at least 0.005 percent by weight, based on the weight of the titanium-containing compound and the sodium phosphate.

According to the invention, the aqueous starting solutions or dispersions so much gelatin was added that the resulting solid activating agent 0.1 to Contains 8 percent by weight gelatin.

Sodium, potassium and ammonium alginates are particularly suitable as salts of polyuronic acids. They are added to the starting solutions in such amounts that after evaporation into the solid Activation agents 0.01 to 1 percent by weight alkali metal alginate or ammonium alginate is included.

The starting solutions are also added so much sodium carbonate or sodium hydroxide that one

1 percent by weight solution of the resulting solid activating agent has a pH in the range of 7.3 to 12.0, preferably a pH of 10.0.

The solid activating agents are expediently prepared in accordance with the method described below Way of working.

The titanium component is dissolved or dispersed in water. Then there will be so much disodium phosphai admitted that to 1 gram atom of titanium approximately

2 moles of disodium phosphate are omitted. After adding the appropriate amount of gelatine or alginate, also Dissolved in water, the mixture thus obtained is stirred for 20 to 45 minutes on a Temperature in the range of 45 to 80 C, preferably 60 C, held. The pH of this mixture should be between 5 and 8.

Then sodium carbonate or sodium hydroxide and the remaining disodium phosphai are added. The mixture thus obtained is under normal pressure at 80 to 110 C, preferably at 95 C, under evaporated to dryness with constant stirring. When drying is carried out at reduced pressure the temperature range is correspondingly lower.

It is possible to have the activating treatment of the metal surfaces as a separate process step to be carried out between alkaline cleaning and phosphating. In this case the Workpieces treated with common alkaline cleaning solutions, then rinsed with water and then Treated with activating solutions for 0.5 to 2 minutes at 20 to 90 C, which are normally used contain only the titanium-containing activating agent in quantities of 0.05 to 5 g / l. These solutions have one pH in the range from 7.0 to 10.5. The workpieces treated in this way are usually without further Intermediate rinse phosphated.

The activating pretreatment of the metal surfaces can also be carried out at the same time as the alkaline Cleaning and degreasing can be carried out. In this case the \ used contain cleaning solutions in addition to the usual ingredients, the activating agent containing thiian in amounts of 0.05 to 5.0 g / l. These solutions can be alkali hydroxide, alkali carbonate, alkali hydrogen carbonate, Alkali orthophosphate, alkali pyrophosphate, alkali tripolyphosphate, alkali hexametaphosphate, Alkali borate and alkali silicate containing the sodium compounds in general the preference is given. The compounds mentioned can be used individually or in the cleaning solutions Mixture be present. The cleaning solutions also contain anion-active and non-ionic Wetting agents. The anion-active wetting agents are mainly alkylbenzenesulfonates, in particular tetrapropylenebenzene, Cerylbenzene and dodecylbenzenesulfonate in question. Suitable nonionic wetting agents are, for example the reaction products of ethylene oxide

»° with fatty alcohols, alkylphenols, fatty amines, fatty acid amides and polyoxypropylene glycol with a molecular weight of 900 to 3000. The cleaning and activating solutions contain the usual ingredients mentioned in the usual concentrations.

The working pH is in the range from 7.5 to 11. The treatment temperature can be 40 to 85 C, the Treatment time is 1 to 15 minutes.

After activating cleaning, the metal surfaces are usually rinsed with water and then phosphated.

Both types of activating pretreatment can be carried out by immersion or spraying will.

The zinc phosphate layers are applied to the metal surfaces using known methods. Solutions are used that contain acidic zinc phosphate and at least one of the formation of the Contain layer accelerating agent. Oxidizing agents such as nitrate are used as accelerators, Chlorate and hydrogen peroxide as well as the combination of nitrite-nitrate, nitrate-chlorate and nitrate-perborate to use. Furthermore, organic compounds such as organic nitro compounds and Metal ions such as nickel or copper ions as accelerators suitable. Combinations of oxidizing agents and metal ions are also possible. The concentration of the phosphating solutions is preferred when used by spraying 10 to 25 points, i.e. H. it is adjusted so that 10 ml of solution are titrated against phenolphthalein Use 10 to 25 ml n / 10 NaOH as an indicator. The phosphating is done in the immersion process carried out, the concentration is preferably 20 to 50 points.

Following the phosphating, the Metal surfaces rinsed with water, if necessary with chromic acid or chromic acid-phosphoric acid solution aftertreated in the usual way or with demineralized water and, if necessary, dried.

With the help of the new process, finely crystalline zinc phosphate layers can be applied to iron, steel and hot-dip galvanized materials Material are generated. The coatings produced have - with a completely closed layer - a lower layer weight than that obtained using the known titanium-containing activating agents Layers. They are especially special as a basis for electrophoretically applied lacquer coatings suitable.

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Example 1 Example 4

Test strips made of hot-dip galvanized sheet iron were tested at 60 ° C. in 36 ml of water solved. The gelatin solution was at a temperature of 45 see long at 65 C by spraying with a temperature of 50 to 60 C treated with a solution of 7.4 g of 5 alkaline, silicate-free cleaning solution, Titanyl sulfate and 15.2 g disodium phosphate in 52.8 ml the 4 g / l solid detergent of the following water combined and then stirred for 0.5 h. The composition contained: 72.0 g of disodium phosphate and 14.6 g percent by weight were then used

Sodium carbonate sprinkled in and the obtained gel sodium hydroxide 10

mixed evaporated to dryness at 95 ^{r C.} The obtained sodium gluconate 5

tene product was ground (product A). Trisodium phosphate 50

Sodium tripolyphosphate 20

Example 2 alkylaryl polyglycol ethers

0.2 g of commercial sodium alginate were in _t (nonylphenol + 13 mol of ethylene oxide). 15th

52.8 ml of water dissolved. The alginate was at ⁱ⁵ _{After Ejner clipboard} enspülune with water were the

a temperature of 50 to 60 C with a solution _Testb | _ec he by spraying for 45 seconds at 35 ° C

from 7.4 g of titanyl sulfate and 15.2 g of disodium phosphate in _{one solution treat >} the 2 e / 1 of product A

combined in 52.8 ml of water and then held for 0.3 h _{. The solution} had a pH of 9.0.

touched. After sprinkling v _O 73.8 disodium n _{ao For} comparison, a portion of the metal strip under

and 14.6 g of sodium carbonate, the resulting _{mixture was treated} with a solution under equal conditions.

evaporated to dryness at 95 C and the _{activating agent containing dek dje dn titari of} the same

ground product obtained (product B). ^ _Composition like product A, but without

_{R. o} . . - Gelatin additive, contained.

Example J _{25 D} j _{e] n} ^ _Q ^ _en pretreated in the manner described

Sheet iron strips of the deep-drawing güle ST 1405 were test sheets in the spray process for 45 seconds

1.5 min at 60 C by spraying with an alkali 60 C with an acidic phosphating solution.

ical cleaning solution that treats 3 g / l solid of the composition:

Cleaning agents with the following composition - „e / 1 ZnO

^{held: 30} 9 ^ 8 g / l H ₃ PO ₁

Weight percent 0.75 g / l HNO ₃

Alkylaryl polyglycol ether 0.5 g / l NiO

(Nonylphenol-f 13 mol ethylene oxide). 8 0.6 g / l H ₂ SiF ₆

Disodium phosphate 70 0.3 g / l NaNO ₂

Sodium hydrogen carbonate 22 ³⁵ 0.6 g / l NaOH

After an intermediate rinse with water, after a subsequent rinse with cold water

the iron sheet strips sprayed for 2 minutes, the sheets were dried with warm air,

treated at 35 C with solutions that each treat 2 g / l of the die with the known activating solution

Product A or B contained. These solutions had four-fold plates and had a layer weight of 3.48 g / m ²

a pH of 9.0. that had been treated with the product A panels

For comparison, sheet iron strips with a layer weight of 2.63 g / m ^{2 were used} . This means that otherwise the same conditions were treated with a solution. Layer weight reduction by 24.5%. delt, which contained a titanium-containing activating agent of the same composition as product A, but without the addition of gelatin.

The test strips made of sheet steel, pretreated in the manner described above, were used for 1.5 minutes at

Test panels were sprayed for 2 minutes at 65 C in the spray process with an alkaline cleaning agent

60 C with an acidic phosphating solution that contains 3 g / l of solid cleaning agent

Treated the composition: 5 "medium of the following composition contained:

6.0 g / l ZnO weight percent

15.0 g / l H ₃ PO ₄ Non-ionic wetting agent (tridecyl-

3.7 g / l HNO ₃ alcohol f 10 mol ethylene oxide

0.5 g / l NaNO ₂ 4-6 mol propylene oxide) 8

1.3 g / l NaOH ⁵⁵ disodium phosphate 65

.,, ,,. η j η, it sodium hydrogen carbonate 21

After a subsequent rinse with cold titanium-containing activating agent

The sheets were dried with warm air in water. (Product A) 6

The sheets treated with the known activating ^{solution had a layer weight of 3.23 g / m 2} 6o. The test strips were then rinsed with cold water, the sheets treated with product A and then a layer weight of 2.0 g for 2 minutes by spraying / m ² , the sheets treated with the product at 60 ° C. with the acidic phosphating solution product B had a layer weight from Example 3 treated. The steel sheet strips were 2.05 g / m ² . In the case of gelatin, this means rinsing with cold water and drying a layer of hot air in the activating agent.

reduction of 38%, in the case of the alginate-containing

Activators of a layer weight reduction strip a zinc phosphate layer with a middle

.. _m iA s ° / layer weight of 2.88 g / m ² generated.

7 8

For comparison, steel sheets were found to have a zinc phosphate

Under the same conditions with a cleaning solution layer with an average layer weight of

iindcll, which has a titanium-containing activation level of 3.66 g / m-.

: hen composition as product A, however, by using product A

e Gclatine / .usat /, and then, like 5, a Schiclitgcwiditsvcrinindcrung of 21.3 "

n described phosphated. After this handling / I will.

Claims (8)

1 2 Processes are already known in which the claims: Metal surfaces for the purpose of activation with solutions containing titanium salt and sodium phosphate 1. Process for the application of fine crystals. This procedural step has the effect that linen, even zinc phosphate layers on 5 during the subsequent phosphating the formation Surfaces made of iron, steel and hot-dip galvanized the phosphate layer is accelerated. Furthermore The materials generated by treating with aqueous alkaline are the solutions generated on the activated metal surfaces, which is an activating agent based on th conversion coatings, particularly dense and fine titanium salt and sodium phosphate, and crystalline. However, the activating effect is only a subsequent phosphating, which is then obtained when the pretreatment results in solutions characterized in that the surfaces with a dried titanium-containing sodium phosphate solutions treated, which an activation salt are produced. A method of manufacture Medium consisting essentially of titanium salt, sodium activation mixtures of titanium salt and naphosphate and gelatin or alkali metal salts triumphosphat is, for example, from the German or ammonium salts, derived from polyuronic acids 15 Auslegeschrift 11 44 565 known. The activating hold, whereby the activating agent is steamed by pretreating the metal surfaces an aqueous solution to dry-ring solutions of the activation mixture between is made. alkaline degreasing and phosphating 2. The method according to claim 1, characterized thereby carried out. The activation can also be done with draws that the metal surfaces are coupled with solutions ao the alkaline cleaning by be treated in which a solid activating one uses alkaline cleaning baths, the one agent is dissolved containing 0.1 to 8 percent by weight corresponding amount of the activating agent. Contains gelatin. Performed with activating pretreatment 3. The method according to claim I, characterized in that phosphating processes enable production draws that the metal surfaces with solutions 25 of conversion coatings that are thinner than the are treated, in which a solid activation layer obtained by other common methods! is solved, the 0.01 to 1 percent by weight. In more recent times, especially in the context of sodium, Potassium or ammonium alginate is often associated with electrophoretic painting holds. preference is given to thin phosphate densities. It has 4. The method according to claim 1 to 3, characterized in that there is no lack of attempts to determine the layer weight characterized in that the activating treatment continues while maintaining a closed coating between the alkaline degreasing and the phos- to decrease. It has been shown that the phation takes place. Weight of zinc phosphate layers that avenge one 5. The method according to claim 1 to 4, characterized by activation with titanium salt and sodium phosphate characterized in that the metal objects are applied according to 35 the metal surfaces, via a the activating treatment cannot be reduced beyond a certain value beyond rinsing with a phosphate solution. Attempts are made to lower the layer weight further will. zcn, no connected zinc 6. The method according to claim 1 to 3, thereby receiving more phosphate layers. characterized that the metal surfaces before the 40 It has now been found that it is possible that Phosphating with alkaline, the activation layer weight of zinc phosphate coatings on iron, cleaning solutions containing agents to further reduce steel and hot-dip galvanized material treated, that and still a finely crystalline, closed one 7. The method according to claim 1 to 6, characterized in that the top layer is obtained when the that used in the spray process as Phos 45 standing process described. The new phating solution a process containing accelerators for the application of finely crystalline, Zinc phosphate solution in a concentration of even zinc phosphate layers on surfaces 10 to 25 points is used. made of iron, steel and hot-dip galvanized material 8. The method according to claim I to 6, characterized by treating with aqueous alkaline solutions that a characterized in that in the immersion process as a phosphate 50 activating agent based on titanium salt and naphatizing solution contain an accelerator containing triumphosphate, and a subsequent zinc phosphate solution in a concentration of phosphating is characterized in that the 20 to 50 points is used. Surfaces are treated with solutions that are a Activating agent consisting essentially of titanium salt, sodium phosphate and gelatin or alkali metal salts or ammonium salts of polyuronic acids, the activating agent by a evaporate an aqueous solution to dryness is made. 60 The solid activating agents are obtained by evaporation of solutions or dispersions containing a titanium compound, sodium phosphate, gelatin or The invention relates to a method for applying alkali metal salts or ammonium salts from PoIygen of finely crystalline, closed zinc phosphaturonic acids and optionally sodium carbonate or coatings on surfaces made of iron, steel and hot 65 contain sodium hydroxide. Galvanized material, in which the metal surfaces As the titanium component are preferably soluble before phosphating with an activating solution, compounds of titanium such as potassium titanium fluoride and be treated. especially titanyl stlfai is used.