DE102017208802A1 - Process for corrosion-protecting phosphating of a metallic surface with reduced pickling removal - Google Patents

Abstract

The present invention relates to a process for anticorrosive phosphating of a metallic surface in which the surface is contacted successively with the following aqueous compositions: i) an alkaline or acidic cleaner composition, ii) a first rinse composition, iii) optionally a second rinse composition, iv ) an acid phosphating composition, v) optionally a third rinsing composition, and vi) a composition containing a (meth) acrylate- and / or epoxide-based CTL, wherein the activating composition i) an activating agent is added and / or wherein the metallic surface between the contacting with the first rinsing composition ii) or optionally the second rinsing composition iii) and the phosphating composition iv) is brought into contact with an aqueous activating composition vii), wherein at least one of the compositions i) to v) at least at least one compound of the formula I contains R1O- (CH2) xZ- (CH2) y-OR2 (I), and wherein R1 and R2 are each independently H or an HO- (CH2) w group with w≥2, x and y are each independently 1 to 4, and Z is an S atom or a C-C triple bond, and an aqueous composition for reducing pickling in the corrosion-protective phosphating of metallic surfaces.

Description

The invention relates to a process for the corrosion-protective phosphating of a metallic surface and to an aqueous composition for the reduction of pickling in the corrosion-protective phosphating of metallic surfaces.

In the corrosion-protective phosphating of metal strips and metallic components - such as those used in vehicle construction - aqueous cleaning and phosphating solutions are used, which have a pH in the clearly acidic or alkaline range or in the clearly acidic range.

During cleaning, the acidic or alkaline pH initially serves to remove oxide films and impurities from the metallic surface. During the subsequent acid phosphating, the oxidative proton attack on the metallic surface itself causes the metal cations necessary for the formation of the phosphate coating to be dissolved out of it (so-called anodic metal dissolution).

In other words, there is a pickling of the metallic surface. Such can take place not only in the phosphating but also in the cleaning, namely, when the metallic surface itself is attacked after the removal of oxide films and impurities.

This raises the problem that the metallic surface receives an uneven morphology due to excessive pickling removal, which translates to the deposited coatings, in particular phosphate coatings insofar that they also have a certain unevenness. This in turn leads to a reduction in the adhesion of subsequent coatings, in particular cathodic electrodeposition paints, and, associated therewith, the corrosion protection.

The object of the invention was therefore to provide a method for corrosion-protective phosphating a metallic surfaces with reduced pickling and a composition for reducing the pickling in the corrosion-protective phosphating metallic surfaces available.

This object is achieved by a method according to claim 1, a composition according to claim 20, a concentrate according to claim 21 and a use according to claim 22. Advantageous embodiments are each described in the dependent claims.

• i) einer alkalischen oder sauren Reinigerzusammensetzung,
• ii) einer ersten Spülzusammensetzung,
• iii) gegebenenfalls einer zweiten Spülzusammensetzung,
• iv) einer sauren Phosphatierzusammensetzung,
• v) gegebenenfalls einer dritten Spülzusammensetzung und
• vi) einer Zusammensetzung enthaltend einen (meth)acrylat- und/oder epoxidbasierten KTL, wobei der Reinigerzusammensetzung i) ein Aktivierungmittel zugegeben wird und/oder wobei die metallische Oberfläche zwischen dem Inkontaktbringen mit der ersten Spülzusammensetzung ii) oder gegebenenfalls der zweiten Spülzusammensetzung iii) und der Phosphatierzusammensetzung iv) mit einer wässrigen Aktivierungszusammensetzung vii) in Kontakt gebracht wird, wobei mindestens eine der Zusammensetzungen i) bis v) mindestens eine Verbindung der Formel I R¹O-(CH₂)_x-Z-(CH₂)_y-OR² (I) enthält, und wobei R¹ und R² jeweils unabhängig voneinander H oder eine HO-(CH₂)_w-Gruppe mit w ≥ 2 sind, x und y jeweils unabhängig voneinander 1 bis 4 sind, und Z ein S-Atom oder eine C-C-Dreifachbindung ist.

In the method according to the invention for the corrosion-protective phosphating of a metallic surface, the surface is brought into contact successively with the following aqueous compositions:

• i) an alkaline or acidic cleaner composition,
• ii) a first rinse composition,
• iii) optionally a second rinse composition,
• iv) an acid phosphating composition,
• v) optionally a third rinse composition and
• vi) a composition comprising a (meth) acrylate and / or epoxide-based KTL, wherein the activating composition i) an activating agent is added and / or wherein the metallic surface between the contacting with the first rinsing composition ii) or optionally the second rinsing composition iii) and the phosphating composition iv) is brought into contact with an aqueous activating composition vii), wherein at least one of the compositions i) to v) comprises at least one compound of the formula I R ¹ O- (CH ₂ ) _x -Z- (CH ₂ ) _y -OR ² (I) and wherein R ¹ and R ^{2 are} each independently H or an HO- (CH ₂ ) _w group with w ≥ 2, x and y are each independently 1 to 4, and Z is an S atom or a CC Triple bond is.

definitions:

In the present case, an "aqueous composition" is to be understood as meaning that, for the most part, i. contains more than 50 wt .-% as a solvent / dispersant water. Preferably, the aqueous composition is a solution, more preferably a solution containing only water as the solvent.

That the metallic surface is successively contacted with the aqueous compositions i) to vi) does not exclude that it is brought into contact with one or more further compositions before and / or after this sequence. Also, it is not excluded that the metallic surface between the contacting with the different compositions i) to vi) is brought into contact with one or more further compositions.

The at least one compound of formula I acts as a physical corrosion inhibitor by Van der Waals forces on the metallic Surface is adsorbed, thereby forming a monomolecular, homogeneous, densely packed layer on this. By means of said layer, the metallic surface is physically shielded from a proton or hydroxide ion attack and thus the pickling of the surface is prevented or at least reduced.

According to a first preferred embodiment, the detergent composition i) contains at least one compound of the formula I.

The concentration of the at least one compound of the formula I in the detergent composition i) is preferably in the range from 6 to 625 mg / l, particularly preferably in the range from 31 to 313 mg / l (calculated as 2-butyne-1,4-diol ).

According to a second preferred embodiment, the first rinsing composition ii), the second rinsing composition iii) and / or the third rinsing composition v) comprises at least one compound of the formula I.

The use of the at least one compound of formula I in one or more of the rinse compositions has the advantage of reducing the formation of flash rust on steel and / or galvanized steel.

The concentration of the at least one compound of the formula I is in the first rinsing composition ii), in the second rinsing composition iii) and in the third rinsing composition v) preferably in the range from 1 to 100 mg / l, particularly preferably in the range from 6 to 60 mg / L (calculated as 2-butyne-1,4-diol).

According to a third preferred embodiment, the phosphating composition iv) comprises at least one compound of the formula I.

The concentration of the at least one compound of the formula I in the phosphating composition iv) is in the range from 1 to 100 mg / l, preferably in the range from 1 to 10 mg / l (calculated as 2-butyne-1,4-diol).

In the method according to the invention, the metallic surface must be activated for the phosphating. This can be done by adding to the detergent composition i) an activating agent and / or bringing the metallic surface into contact with the first rinsing composition ii) or optionally the second rinsing composition iii) and the phosphating composition iv) with an aqueous activating composition vii) ,

The activation serves to deposit a multiplicity of the finest phosphate particles as seed crystals on the metallic surface. These help in the process step of phosphating, ie in contact with the phosphating iv) - preferably without intermediate rinsing - form a particular crystalline phosphate layer with the highest possible number of densely arranged fine phosphate crystals or a largely closed phosphate layer.

According to a first preferred embodiment, the cleaning composition is added to an activating agent, in particular titanium phosphate or zinc phosphate, ie purification and activation are carried out in one step.

According to a second, further preferred embodiment, the metallic surface is brought into contact with the first rinsing composition ii) or optionally the second rinsing composition iii) and the phosphating composition iv) with an aqueous activating composition vii).

Particularly suitable as activating compositions are acidic or alkaline compositions based on titanium phosphate or zinc phosphate.

Optionally, the metallic surface is brought into contact with the first rinsing composition ii) or optionally the second rinsing composition iii) and the phosphating composition iv) with an aqueous pickling composition viii) and then with a fourth rinsing composition ix). However, contacting with the pickling composition viii) is in any case preceded by contacting with the activating composition vii).

However, it is also possible to contact the metallic surface before contacting it with the detergent composition i) with an aqueous pickling composition viii) and then a fourth rinsing composition ix).

The pickling composition viii) preferably contains at least one compound selected from the group consisting of phosphonates, condensed phosphates and citrate and / or at least one mineral acid selected from the group consisting of sulfuric acid, hydrochloric acid, hydrofluoric acid and nitric acid, more preferably it contains at least one mineral acid selected from the group consisting of sulfuric acid, hydrochloric acid, hydrofluoric acid and nitric acid, most preferably it contains sulfuric acid.

According to a further embodiment, the pickling composition viii) contains at least one compound of the formula I.

The concentration of the at least one compound of the formula I in the mordant composition viii) is in the range from 31 to 620 mg / l, preferably in the range from 31 to 310 mg / l (calculated as 2-butyne-1,4-diol).

The use of the at least one compound of the formula I in the pickling composition has the advantage of particularly effectively reducing pickling.

Alternatively or additionally, however, the fourth rinsing composition ix) may also contain at least one compound of the formula I.

Preferably, the detergent composition is i) alkaline, more preferably has a pH of 9.5 or greater.

The first rinsing composition ii), the second rinsing composition iii) and the third rinsing composition v) preferably have a pH in the range from 2 to 10, more preferably in the range from 3 to 10.

The first rinse composition is preferably weakly acidic, slightly alkaline or neutral. Particularly preferably, it has a pH in the range from 6 to 9.

The second rinse composition is preferably weakly weakly alkaline or neutral. Most preferably, it has a pH in the range of 7 to 9.

The third rinse composition preferably has a pH in the range of 4 to 9, more preferably it is slightly acidic, slightly alkaline or neutral. Most preferably, it has a pH in the range of 6 to 8.

The phosphating composition iv) may contain zinc phosphate (so-called zinc phosphating) or an alkali metal phosphate (so-called iron phosphating). It preferably contains zinc phosphate and optionally manganese phosphate and / or nickel ions.

Most preferably, the phosphating composition contains iv) zinc phosphate and manganese phosphate and is substantially nickel free, i. it contains less than 0.3 g / l nickel ions.

It very particularly preferably contains 0.3 to 3.0 g / l of zinc ions, 0.3 to 2.0 g / l of manganese ions and 8 to 25 g / l of phosphate ions (calculated as P ₂ O ₅ ).

When the phosphating composition iv) is a substantially nickel-free phosphating composition containing zinc phosphate and manganese phosphate, it is advantageous to subsequently contact the metallic surface with a third rinse composition v) containing molybdenum ions and / or zirconium ions.

In this way, paint adhesion and corrosion protection results can be achieved, which are comparable to those of a nickel-containing reference system.

The molybdenum ions are preferably added as molybdate, more preferably as ammonium heptamolybdate and particularly preferably as ammonium heptamolybdate x 7 H ₂ O of the third rinsing composition v). The molybdenum ions can also be added as sodium molybdate.

However, molybdenum ions can also be added, for example, in the form of at least one salt containing molybdenum cations, such as molybdenum chloride, to the third rinse composition v) and then oxidized to molybdate by a suitable oxidizing agent. In such a case, the third rinse composition v) itself contains a corresponding oxidizing agent.

More preferably, the third rinse composition contains v) molybdenum ions and / or zirconium ions, most preferably molybdenum ions in combination with zirconium ions, wherein the content of molybdenum ions and zirconium ions is in the range of 10 to 500 mg / l each (calculated as metal).

The content of molybdenum ions is preferably in the range from 20 to 225 mg / l, particularly preferably from 50 to 225 mg / l and very particularly preferably from 100 to 225 mg / l and the content of zirconium ions in the range from 50 to 300 mg / l. l, more preferably from 50 to 150 mg / l.

Preferably, the at least one compound of the formula I is a mixture of a compound of the formula I in which R ¹ and R ^{2 are} both H, and a compound of the formula I in which R ¹ and R ^{2 are} each independently an HO- CH ₂ ) _w group with w ≥ 2.

In this case, based on wt .-% mixing ratio of the compound of formula I in which R ¹ and R ^{2 are} both H, and the compound of formula I in which R ¹ and R ^{2 are} each independently a HO- (CH ₂ ) _w group with w ≥ 2, in the range of 0.5: 1 to 2: 1, preferably in the range of 0.75: 1 to 1.75: 1 and particularly preferably in the range of 1: 1 to 1, 5: 1 (calculated as 2-butyne-1,4-diol and 2-butyne-1,4-diol-bis (2-hydroxyethyl ether)).

Preferably, in the at least one compound of formula IR ¹ and R ^{2 are} both H or an HO- (CH ₂ ) ₂ group, the sum of x and y is 2 to 5, and Z is a CC triple bond.

More preferably, the at least one compound of the formula I is 2-butyne-1,4-diol and / or 2-butyne-1,4-diol bis (2-hydroxyethyl ether).

The at least one compound of the formula I is particularly preferably a mixture of 2-butyne-1,4-diol and 2-butyne-1,4-diol bis (2-hydroxyethyl ether), the mixing ratio based on wt Range of 0.5: 1 to 2: 1, preferably in the range of 0.75: 1 to 1.75: 1 and more preferably in the range 1: 1 to 1.5: 1.

The metallic surface treated with the method according to the invention is preferably the surface of a metal strip or a metallic component, for example a body.

The metallic surface may include bare steel, electrolytically galvanized and / or hot-dip galvanized steel, aluminum and / or an aluminum alloy.

According to a preferred embodiment, in addition to bare steel and / or galvanized steel, the metallic surface also contains aluminum or an aluminum alloy (so-called multimetal capability).

The process according to the invention has proved to be advantageous in the case of acrylate- and / or epoxide-based cathodic electrocoating paint (EPC) in terms of improved paint adhesion and improved corrosion protection.

Subsequently, a topcoat is optionally applied to the KTL-painted metallic surface.

The present invention also relates to an aqueous composition for reducing pickling in the corrosion-protective phosphating of metallic surfaces, which contains at least one compound of the formula I as described above.

In addition, it relates to a concentrate from which the aqueous composition according to the invention can be obtained by dilution with a suitable solvent and / or dispersion medium, preferably with water, and optionally adjusting the pH.

The dilution factor is preferably in the range from 1:10 to 1: 10,000, more preferably in the range from 1:50 to 1: 200.

Finally, the present invention also relates to the use of the metallic surface treated by the method according to the invention.

Claims (22)

Process for the corrosion-protective phosphating of a metallic surface, characterized in that the surface is brought into contact successively with the following aqueous compositions: i) an alkaline or acidic cleaning composition, ii) a first rinsing composition, iii) optionally a second rinsing composition, iv) an acidic one Phosphating composition, v) optionally a third rinsing composition and vi) a composition containing a (meth) acrylate and / or epoxide-based CTL, wherein the activating composition i) an activating agent is added and / or wherein the metallic surface between the contacting with the first rinsing composition ii ) or optionally the second rinsing composition iii) and the phosphating composition iv) with an aqueous activating composition vii), wherein at least one of the compositions i) to v) at least one Verbindu of the formula I R ¹ O- (CH ₂ ) _x -Z- (CH ₂ ) _y -OR ² (I) and wherein R ¹ and R ^{2 are} each independently H or an HO- (CH ₂ ) _w group with w ≥ 2, x and y are each independently 1 to 4, and Z is an S atom or a CC Triple bond is. A method according to claim 1, characterized in that the cleaning composition i) contains at least one compound of formula I. A method according to claim 2, characterized in that the concentration of the at least one compound of formula I in the range of 6 to 625 mg / l, preferably in the range of 31 to 313 mg / l (calculated as 2-butyne-1,4-diol ) lies. Method according to one of the preceding claims, characterized in that the first rinsing composition ii), the second Rinsing composition iii) and / or the third rinsing composition v) contains at least one compound of formula I. A method according to claim 4, characterized in that the concentration of the at least one compound of formula I in the range of 1 to 100 mg / l, preferably in the range of 6 to 60 mg / l (calculated as 2-butyne-1,4-diol ) lies Method according to one of the preceding claims, characterized in that the phosphating composition iv) contains at least one compound of formula I. A method according to claim 6, characterized in that the concentration of the at least one compound of formula I in the range of 1 to 100 mg / l, preferably in the range of 1 to 10 mg / l (calculated as 2-butyne-1,4-diol ) lies. Method according to one of the preceding claims, characterized in that the activating agent contained in the detergent composition i) or in the activating composition vii) is titanium phosphate or zinc phosphate. Method according to one of the preceding claims, characterized in that the cleaning composition i) is alkaline, preferably has a pH of 9.5 or more. Method according to one of the preceding claims, characterized in that the first rinsing composition ii) has a pH in the range of 6 to 9, the second rinsing composition iii) a pH in the range of 7 to 9 and the third rinsing composition v) a pH Value in the range of 4 to 9. Method according to one of the preceding claims, characterized in that the phosphating composition iv) 0.3 to 3.0 g / l of zinc ions, 0.3 to 2.0 g / l of manganese ions and 8 to 25 g / l of phosphate ions (calculated as P ₂ O ₅ ) and is substantially free of nickel. Method according to one of the preceding claims, characterized in that the metallic surface is brought into contact with a third rinsing composition v) containing molybdenum ions and / or zirconium ions, wherein the content of molybdenum ions in the range of 20 to 225 mg / l (calculated as Metal) and the content of zirconium ions is in the range of 50 to 300 mg / l (calculated as metal). A method according to claim 12, characterized in that the third rinsing composition contains v) molybdenum ions in combination with zirconium ions. Method according to one of the preceding claims, characterized in that the at least one compound of formula I is a mixture of a compound of formula I, wherein R ¹ and R ^{2 are} both H, and a compound of formula I, wherein R ¹ and R ^{2 are} each independently an HO (CH ₂ ) _w group with w ≥ 2. A process according to claim 14, characterized in that the mixing ratio of the compound of the formula I in which R and R ^{2 are} both H and the compound of the formula I in which R ¹ and R ^{2 are} each independently, based on wt from each other are an HO- (CH ₂ ) _w group with w ≥ 2, in the range of 0.5: 1 to 2: 1, preferably in the range of 0.75: 1 to 1.75: 1 and more preferably in the range from 1: 1 to 1.5: 1 (calculated as 2-butyne-1,4-diol and 2-butyne-1,4-diol bis (2-hydroxyethyl ether)). Method according to one of the preceding claims, characterized in that in the at least one compound of formula IR ¹ and R ^{2 are} both H or a HO- (CH ₂ ) ₂ group, the sum of x and y is 2 to 5, and Z is a CC double bond. A method according to claim 16, characterized in that the at least one compound of formula I is 2-butyne-1,4-diol and / or 2-butyne-1,4-diol bis (2-hydroxyethyl ether). Process according to Claim 17, characterized in that the at least one compound of the formula I is a mixture of 2-butyne-1,4-diol and 2-butyne-1,4-diol bis (2-hydroxyethyl ether). Method according to one of the preceding claims, characterized in that the metallic surface in addition to bare steel and / or galvanized steel also contains aluminum or an aluminum alloy. Aqueous composition for reducing pickling in the anticorrosion treatment of metallic surfaces, characterized in that it contains at least one compound of formula I according to claim 1 or one of claims 14 to 18. Concentrate from which a composition according to claim 20 can be obtained by dilution with a suitable solvent and / or dispersion medium and optionally adjusting the pH. Use of the treated with a method according to any one of claims 1 to 19 metallic surface.