Zn-flakes stabilized by an additive for aqueous based corrosion formulations

Abstract

This invention is directed to a zinc pigment or zinc alloy pigment suitable for aqueous based corrosion paint formulations, wherein the zinc flake is at least partially coated with an additive which is based on an oligomeric polyester of fatty acids which is at least partially phosphated or phosphonated and comprises at least a first polyester component or a mixture of different components being represented by the following formula (Ia) and optionally also a second polyester component or a mixture of different components being represented by the following formula (Ib) wherein: R1 is an alkyl moiety from 4 to 10 C-atoms, R2 is an aliphatic moiety from 8 to 14 C-atoms, A is a group independently chosen from any member of the group consisting of - O-PO(OR3)2, -PO(OR3)2, -OR3 or -O-CO-R4, R3 is independently H, methyl or ethyl or protonated amines, R4 is an aliphatic moiety having 15 to 21 C-atoms, x is an integer in the range of 1 to 10 and y is an integer in the range of 0 to 10 with the proviso, that for y=0 A cannot be -O-CO-R4.

Description

[0001] Zn-flakes stabilized by an Additive for aqueous based Corrosion Formulations

[0002] The invention relates to zinc flakes having a coating for corrosion protection. These protected zinc flakes can be used in aqueous based corrosion protection formulations.

[0003] Metallic substrates like coils can be protected against corrosion by using passivating substances such as phosphonates or phospates. For example EP 0760387 B1 discloses an anti-corrosive pigment comprising a polyvalent metal organophosphonate wherein the organophosphonate corresponds to phosphono carboxylic acid containing one or more acid groups and the ratio of polyvalent metal in said organophosphonate to acid group or groups in the corresponding phosphono carboxylic acid is 1.25:1 to 6:1 on an equivalents basis when taking into account the metal's valence. This anti-corrosive pigment intends to replace traditional corrosion pigments like zinc. They are not used in combination with zinc flakes.

[0004] EP 2598582 B1 discloses a method for the corrosion-inhibiting coating of metal surfaces, characterized in that

[0005] (1) in a first step, the metal surface is cleaned and optionally treated with a pretreatment composition, and

[0006] (2) in a second step, the metal surface cleaned and optionally pretreated in step (1) is coated with a primer (p) comprising at least one binder (bm) and at least one crosslinking agent (v), and also at least one phosphorus-containing polyester component (a), wherein (a) is an acidic esterification product of phosphonic acid, of monophosphoric acid and / or of polyphosphoric acid, and / or of the anhydrides thereof and / or of the esters thereof, with at least one polyester (b) which contains at least two hydroxyl groups, and the drying and / or curing of the primer is carried out at peak temperatures (peak metal temperature (pmt)), found beforehand on the metal, of at least 80°C.

[0007] The primer described herein is intended to replace conventional metals like zinc as corrosion protection pigment in metal coil applications. No application in water-based corrosion formulations is disclosed. EP 1852453 B1 discloses a powder coating composition having corrosion protection properties comprising certain curing agents and one or more acid functional, phosphorous-containing polyester of distinct properties. No zinc pigments are involved in this compositions.

[0008] Such passivation methods do have the well-known disadvantage that they only protect macroscopic surfaces which do not have a damaged surface like a scratch, for example. Such surfaces are better protected by using metallic pigments such as zinc pigments which act electrochemically as sacrificial anode. When using zinc flakes the oxidation of these pigments leads to a further compaction of the corrosion protection layer which also enhances barrier protection properties. Generally active corrosion protection formulations containing zinc dust particles or zinc flakes are much more efficient than mere passivation formulations based on additives.

[0009] Therefore, inc flakes or zinc alloy flakes have been used for decades as pigments for cathodic corrosion protection. Usually, the corrosion formulations are solvent based systems, but due to ecological demands there is a desire to further shift to water-based corrosion protection formulations. In such formulations it is difficult to stabilize the zinc flakes against attack by water in the corrosion formulation while simultaneously the pigment must act as corrosion pigment in the final application of a film on a steel or an aluminum substrate. Special coatings or treatments of the zinc flakes have been proposed to address this difficult balance.

[0010] JP 3124830 B2 discloses a zinc-containing metal flake having a colloidal silica film on its surface. The coated zinc flake is deemed to be stable in aqueous based formulations and can be used as rust preventive coatings.

[0011] JP 2005238001 A discloses zinc flakes for aqueous based corrosion formulations, wherein the zinc flakes are treated with an oligomeric tetraethoxysilane and a water-soluble silane coupling agent. The coated zinc pigment seems to act as a rust preventive pigment and is stable in water-based formulations. However, many components must be carefully adjusted to obtain the desired properties, making this composition difficult to control and causing problems in reproducibility.

[0012] EP 3315563 A1 discloses zinc flakes which are coated with metal oxides from silicon, titanium or zirconium, preferably of silicon oxide. These pigments also should be stable in aqueous based corrosion formulations and at the same time exhibit good corrosion protection. However, it is difficult to adjust the exact thickness of the metal oxide coating. Thick coatings impart gassing stability but prevent the use as effective corrosion pigment while for thin metal oxide coatings the contrary characteristics apply. Therefore, an optimal metal oxide thickness must be adjusted for every corrosion formulation system which is not practical as the metal oxide coating is made by pigment suppliers while the corrosion formulation is made by coating manufacturers. Additionally, the manufacture of such coated zinc flakes has not been reproducible.

[0013] US 2023 / 0323135 A1 discloses a rust preventive coating composition comprising a zinc pigment which is at least partially treated with orthophosphoric acid. This document indicates that the silica coated zinc pigments either failed to have gassing stability or did not give satisfactory results as corrosion protection pigment. The coating composition disclosed in this document is expected to have stability also in aqueous based formulations. Dispersibility is achieved mainly by adding a further dispersing additive.

[0014] It is an object of the present invention to provide a zinc pigment, preferably a zinc flake or zinc alloy pigment which can be used in corrosion formulations based on aqueous formulations. The zinc pigments, preferably zinc flakes should be easily dispersible in aqueous corrosion formulation and be stable against gassing and agglomeration. The protection should be achieved in a simple manner without the use of too many components.

[0015] The object is solved by providing a zinc pigment or zinc alloy pigment suitable for aqueous based corrosion paint formulations, wherein the zinc flake is at least partially coated with an additive which is based on an oligomeric polyester of fatty acids. The oligomeric polyester of fatty acids is at least partially phosphated or phosphonated and comprises at least a first polyester component or a mixture of different components represented by formula (la):

[0016] R1-CH-(O-CO-R2-CH-)xA (la)

[0017] R2-COOR3R1

[0018] and optionally a second polyester component or a mixture of different components having formula (lb): R4-COO-CH-(O-CO-R2-CH-)yA (lb)

[0019]

[0020] I ,

[0021] wherein: R1is an alkyl moiety from 4 to 10 C-atoms,

[0022] R2is an aliphatic moiety from 8 to 14 C-atoms,

[0023] A is a group independently chosen from any member of the group consisting of O-PO(OR3)2, PO(OR3)2, OR3or O-CO-R4,

[0024] R3is independently H, methyl or ethyl,

[0025] R4is an aliphatic moiety having 15 to 21 C-atoms,

[0026] x is an integer in the range of 1 to 10

[0027] and y is an integer in the range of 0 to 10 with the proviso that for y=0, A cannot be -O-CO-R4.

[0028] In a preferred embodiment the additive further comprises a third component represented by formula (Ila):

[0029] R1-CH-R2-CO-R5-B, (Ila)

[0030]

[0031] and optionally also being represented by formula (lib):

[0032] R4-CO-O-R5-D (lib)

[0033] wherein R5is a monomer moiety comprising a bisphenol A derivate moiety, wherein R6is independently any of OH, O-PO(OR3)2, PO(OR3)2,

[0034] O-CO-R2-CH-OR3or O-CO-R4and

[0035] wherein group B is any of group A or -CO-R2-CH-R1

[0036] OR6

[0037] and wherein group D is any of OH, -O-PO(OR3)2, -PO(OR3)2, or -O-CO-R4. Further preferred embodiments are disclosed in claims 3 to 14.

[0038] The object is further solved by providing a method of manufacture of the additive coated zinc pigments, comprising a mixing step of flaky zinc pigments and the additive.

[0039] Zinc pigment: The term “pigment” or “flake” used herein always include a plurality of these terms.

[0040] Additionally, the terms “platy zinc pigment” and “zinc flake” are used synonymously.

[0041] The zinc pigments may be zinc powder (also called zinc dust), which preferably has spherical geometry. In preferred embodiments the zinc pigment is composed of a mixture of zinc dust and zinc flakes and this mixture preferably contains at least 50 % by weight zinc flakes and more preferably at least 75 % by weight zinc flakes. Even more preferably the zinc pigment contains zinc flakes in a ratio of 98 wt.% to 100 wt.%. and further most preferably the zinc pigments are zinc flakes.

[0042] Zinc flakes have the advantage that they do not act only as corrosion protection pigment in cathodic corrosion protection by acting as sacrificial anode but also impart a barrier effect. A ’’zinc flake” has an aspect ratio (defined as ratio of median size dso to the average thickness tzn of the flakes) of at least 2, preferably at least 5 and most preferably at least 10. For zinc flakes the aspect ratio is usually below 400, more preferably below 300. In other embodiments the aspect ratio is preferably in a range of 4 to 100, more preferably in a range of 5 to 70 and most preferably in a range of 6 to 50.

[0043] The particle size of the zinc pigments can be determined by laser granulometry, preferably using a Helos BR apparatus. As a measure of the mean diameter the median value dso can be used. The sizes are determined as volume weighted sphere equivalents according to the Fraunhofer approximation and according to the instructions of the manufacturer of the measurement instrument. Preferably the dsoof the zinc flakes is in a range of 3.0 to 50 pm, more preferably in a range of 5.0 to 30 pm and most preferably in a range of 7 to 25 pm. Preferably the dso of zinc dust is in a range of 2.0 to 45 pm, more preferably in a range of 2.5 to 30 pm and most preferably in a range of 3.0 to 10 pm.

[0044] The mean thickness tzn of the zinc flakes are preferably in a range of 0.20 to 4.0 pm and more preferably in a range of 0.50 to 3.0 pm. The mean thickness can preferably be determined by SEM measurements using the method described on page 24 of WO 2004 / 087816 A2. The mean thickness is defined as the arithmetical average of all thicknesses counted when measuring the individual thicknesses with SEM.

[0045] In preferred embodiments pure zinc pigments are used. The purity of these zinc flakes is preferably at least 99.99 %, more preferably at least 99.999% and most preferably at least 99.9999 %. In other embodiments zinc alloys may be used. Any alloy can be used in which the content of zinc is at least 50 wt.% of the alloy. An exemplary alloy is represented by the formula (HI):

[0046] ZnAlaMgbSncMfo (III)

[0047] Herein a, b and c denote to the contents of the respective metal in wt.-%, referred to the total content of the alloy, a is in a range of 0 to 10, preferably in a range of 2.5 to 7; b is in a range of 0 to 7, preferably in a range of 0.5 to 6; c is in a range of 0 to 35, preferably in an range of 10 to 30 and o is in a range of 0 to < 2.5, preferably in a range of 0.01 to 0.5 and more preferably in a range of 0.02 to 0.1. Mfdenotes further optional alloy metals which can be treated as a sum and are preferably Ca, Si, In, Bi, Mn, K, Sr, Ba and mixtures thereof, and more preferably Ca, Sn, Si, In, Bi and mixtures thereof. These components often occur as impurities. At least one of the metal contents parameters a, b and c is > 0 and the sum of a + b + c is preferably below of 45.

[0048] The balance of the alloy is always made by zinc and common and unavoidable impurities. Preferred zinc alloys are ZnAh, ZnA , ZnSni5, ZnSnso, ZnMg26 and the like.

[0049] Alloys having a normal potential below of the aluminum normal potential may be used in corrosion protection coatings of aluminum, as described forZnMg alloys in EP 2499205 A1 , for example.

[0050] If zinc dust is used as zinc pigment it will be delivered as powder after it is coated with the additive. Mixtures of zinc dust and zinc flakes or pure zinc flakes coated at least partially by the additive may be a powder or a paste. In case of the paste of the content of zinc flake is preferably in a range of 60 to 95 wt.%, more preferably in a range of 65 to 94 wt.%, even more preferably in a range of 75 to 93 wt.% and most preferably in a range of 80 to 92 wt.%.

[0051] The actual content will be dependent on the particle size and also especially on the thickness of the zinc flakes and also on the solvent used. The paste form has the advantage that the pigment is delivered in a non-dusting form while the content of solvent is as low as possible to minimize solvent emission in the environment.

[0052] Typical solvents used for the paste include, but are not limited to ethanol, n-propanol, isopropanol, n-butanol, isobutanol, diacetone alcohol, amyl alcohol, isoamyl alcohol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, propylene glycol, butyl glycol, polyoxyethylene glycol, and polyoxypropylene glycol or white spirit and mixtures thereof. More preferably the organic solvent is a hydrophilic solvent which may be used singly or in combination of two or more. Preferred examples of the hydrophilic organic solvent are n-propanol, isopropanol, 1-methoxy-2-propanol,1-ethoxy-2-propanol, butyl glycol and mixtures thereof.

[0053] In an embodiment the paste contains the zinc pigments, the additive and solvent in an amount in a range of 98.0 to 100.0 wt.% and more preferably in an amount in a range of 99.0 to 100.0 wt.%, each referred to the total weight of the paste.

[0054] In another embodiment the additive coated zinc flakes may be further processed into a pellet by mixing with a binder and pelletizing this mixture. The binder is most preferably chosen from the binders used in the final corrosion coating as mentioned further below.

[0055] Additive:

[0056] The additive of formula (I) represents oligomeric esters of fatty hydroxycarboxylic acids which are at least partially phosphated or phosphonated.

[0057] R1-CH-(O-CO-R2-CH-)xA (la) R2-COOR3R1

[0058] Herein R1is an alkyl moiety from 4 to 10 C-atoms which can be linear or branched.

[0059] Preferably R1has 6 to 8 C-atoms and preferably is a linear alkyl.

[0060] R2is an aliphatic moiety from 8 to 14 C-atoms, and preferably 10 to 12 C-atoms. Preferred moieties have formulas C10H19, C10H21, C12H21, C12H23 and more preferred these groups are linear alkylene or alkenene moieties.

[0061] The group A is independently chosen from any of -O-PO(OR3)2, -PO(OR3)2, -OR3or -O-CO-R4, wherein R4is an aliphatic moiety with 15 to 21 C-atoms and x is an integer in the range of 1 to 10. Regarding the phosphorous-containing groups the phosphate group -O-PO(OR3)2 is more preferred.

[0062] The term “independently” herein means that some molecules of the additive may have a -O-PO(OR3)2 group, for example, and other molecules may have any of the other groups. The aliphatic moiety R4preferably has 15 to 21 C-atoms and more preferably 16 to 20 C- atoms, even more preferably 17-19 C-atoms and most preferably 18 C-atoms. In most preferred embodiments R4is a linear saturated or unsaturated aliphatic group.

[0063] The moiety R3belongs to a carboxylic group and can be independently H, methyl, ethyl, or protonated amines and more preferably independently H, ethyl, or protonated amines. The term “independently” herein means that some molecules may have a R3= H and other R3= ethyl, for example. Methyl or ethyl groups may be formed from the carboxylic acid form by esterification with a corresponding alcoholic solvent.

[0064] Examples for the protonated amines are amines based preferably on primary amines and are preferably aliphatic amines. The amine used is more preferably an aliphatic primary amine. The protonated amines rely on an amine compound which is not particularly limited, but for example, ethylamine, propylamine, n-butylamine, tert-butylamine, hexylamine, octylamine, decylamine, dodecylamine (laurylamine), tridecylamine, tetradecylamine, hexadecylamine, etc. octadecylamine (stearylamine), isopropylamine, isobutylamine, 2-ethylhexylamine, isotridecylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dihexylamine, dioctylamine, dilaurylamine, ditridecylamine, monoethanol amine, diethanol amine, triethanol amine, ethylendiamine, tri-isopropanol amine, distearylamine, diisopropylamine, diisobutylamine, di (2-ethylhexyl) amine, diisotridecylamine, methylbutylamine, ethylbutylamine, ethylhexylamine, ethyllaurylamine, ethylstearylamine, isopropyloctylamine, isobutyl-2-ethylhexylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, trioctylamine, trilaurylamine, tridecylamine, tristearylamine, triisopropylamine, triisobutylamine, tris (2-ethylhexyl) amine, triisotridecylamine, dimethyloctylamine, dimethyllaurylamine, dimethylstearylamine, diethyllaurylamine, allylamine, diallylamin, urea and so on can be used. As the amine compound, one kind may be used alone, or two or more kinds may be used in combination.

[0065] The parameter x is an integer and is in the range of 1 to 10 and more preferably in a range of 1 to 6. The additive preferably comprises different species with different x-values. In preferred embodiments a maximum of oligomers having a x = 2 can be found in a GPC (Gel Permeation Chromatography) analysis.

[0066] In preferred embodiments the formula (la) represents ester oligomers from hydroxy carboxy acids like ricinoleic acid, 12-hydroxy stearic acid or lesquerolic acid with either themselves or with different species of this group which are partially phosphated and / or phosphonated. Phosphated species may be obtained by esterification with the hydroxyl groups of the carboxylic acids. Phosphonated species may be obtained by substitution of the hydroxy group of an appropriate hydroxy carboxylic acids by bromide followed by an Arbuzov Reaction with a phosphite ester.

[0067] Optionally the additive may also contain a second oligomeric species represented by formula (lb):

[0068] R4-COO-CH-(O-CO-R2-CH-)yA (lb)

[0069]

[0070] i, L

[0071] Herein y is an integer in the range of 0 to 10 with the proviso, that for y=0, moiety A cannot be -O-CO-R4.

[0072] Formula (lb) represents species wherein additional ester oligomers with other fatty carboxy acids are involved by esterification with the hydroxy carboxylic acids. Examples of the fatty acids are behenic acid, arachidonic acid, stearic acid, palmitic acid, gondoic acid, eicosenoic acid, oleic acid, elaidic acid, vaccenic acid, palmitoleic acid, sapienic acid, linoleic acid, linolelaidic acid, a-linolenic acid, y-linolenic acid and the like. Due to the absence of hydroxy groups in these molecules they usually represent a final group R4. In further preferred embodiments the additive further comprises a third component represented by formula (Ila) and / or formula (lib):

[0073] R1-CH-R2-CO-O-R5-B, (Ila)

[0074] k

[0075] Optionally this third component can also comprise oligomers that can be represented by formula (lib):

[0076] R4-CO-O-R5-D (lib)

[0077] Herein O-R5represents a monomer moiety comprising a bisphenol or a bisphenol ether moiety. The oxygen atom represents an oxygen atom either from the bisphenol moiety or from the bisphenol ether moiety in the state that they have reacted with other components to form an ester component of the additive. Examples for such monomeric compounds are bisphenol A, bisphenol AP, bisphenol B, bisphenol BP, bisphenol E, bisphenol F, bisphenol A bis(2-hydroxypropyl), bisphenol AP bis(2-hydroxypropyl), bisphenol B bis(2-hydroxypropyl), bisphenol BP bis(2-hydroxypropyl), bisphenol E bis(2-hydroxypropyl), bisphenol F bis(2-hydroxypropyl), bisphenol A bis(2-hydroxyethyl), bisphenol AP bis(2- hydroxyethyl), bisphenol B bis(2-hydroxyethyl), bisphenol BP bis(2-hydroxyethyl), bisphenol E bis(2-hydroxyethyl) and bisphenol F bis(2-hydroxyethyl) and mixtures thereof. In more preferred embodiments the O-R5moiety comprises a bisphenol A compound. More preferred examples are therefore bisphenol A, bisphenol A bis(2-hydroxyethyl) and bisphenol A bis(2-hydroxypropyl) and most preferred is a bisphenol A bis(2-hydroxypropyl) moiety.

[0078] R6is independently any of OH, -O-PO(OR3)2, -PO(OR3)2, -O-CO-R2-CH-OR3or

[0079] -O-CO-R4. |

[0080]

[0081] R1The group B is any of group A or -CO-R2-CH-R1.

[0082]

[0083] The group D is any of OH, O-PO(OR3)2 -PO(OR3)2, or O-CO-R4.

[0084] Of course, the additive may contain any mixture of species represented by any two or more of the formulas (la), (lb), (Ila) or (lib). Likewise, it may contain different species each represented by the formula (la), different species each represented by the formula (lb), different species each represented by the formula (Ila) and different species each represented by the formula (lib). Additionally other species may be contained which are not represented by any of the formulas (la), (lb), (Ila) or (lib), but will relate to the precursor molecules like free hydroxy carboxylic acids, for example.

[0085] In preferred embodiments the additive contains oligomeric species based on fatty hydroxy acids, wherein the hydroxyl groups are esterified in a range of 30 to 60 mol-% and more preferred in a range of 35 to 55 mol-%.

[0086] In further preferred embodiments the additive contains oligomeric species based on bisphenol A species as represented by formulas (Ila) and / or (lib), wherein the hydroxyl groups of the bisphenol A derivative are esterified in a range of 30 to 60 mol-% and more preferred in a range of 35 to 55 mol-%.

[0087] The term “at least partially phosphated” means that at least 2.5 mol-% and more preferably at least 3.4 mol-% of all of group A and optionally of groups B and D contain a phosphate group. In preferred embodiments a maximum of 15 mol-%, preferably a maximum of 10 mol-% and more preferably a maximum of 7.0 mol-% of all of groups A, B and D contain a phosphate group. In other embodiments group A and optionally groups B and D contain a phosphate group in an amount in a range of 2.5 mol% to 15 mol%, and more preferably in a range of 3.4 to 7.0 mol%, each based on the total of the groups of A and optionally also of groups B and D.

[0088] In preferred embodiments the average molecular weight (number averaged, determined with GPC, based on polystyrol standard) of the additive is in a range of 500 to 1000 g / mol and more preferred in a range of 600 to 800 g / mol. GPC measurements are preferably conducted by using a column set called Styragel (HR4, HR2, HR1) from Waters and tetra hydrofuran with 1 vol.% acetic acid as solvent and eluent at a flow rate of 1 ml / min. The apparatus can be calibrated with polystyrol and a Rl-detector can be used.

[0089] In preferred embodiments the additive is bonded directly on the surface of the zinc flakes. This bonding can be realized by any of chemisorption or physisorption mechanism. The zinc flake is in this case not treated with other corrosion protection means such as a silica coating. Without being bound to a theory it is suspected that the additive is primarily bonded via the phosphoric (or phosphonic) acidic group to the surface of the zinc flakes as these groups are well known to bond on metallic surfaces.

[0090] The term that the zinc pigment is ”at least partially coated with the additive” means that at least 30 %, more preferably at least 50%, even more preferably at least 75% and most preferably at least 90 % of the surface of the zinc pigment is coated with the additive. In preferred embodiments the amount of the additive is in a range of 0.3 to 5.0 wt.%, more preferred in a range of 0.4 to 4.0 wt.% and most preferred in a range of 0.5 to 3.0 wt%, each based to the weight of the zinc pigment. The actual amount of the additive needed depends on the specific area of the zinc pigment to be protected and may by easily adjusted by the skilled person.

[0091] Below of 0.3 wt.% the stabilization of the zinc pigment against gassing in an aqueous corrosion formulation will not be sufficient and above of 5.0 wt.% the zinc pigment may have problems of being compatible with the aqueous based corrosion formulation system and may be stabilized so well so that the pigment does not act sufficiently as corrosion protection pigment any more.

[0092] The gassing stability of the coated zinc pigment may be sufficient if the stabilized pigment is stable for typically at least eight hours in the aqueous based corrosion protection formulation (pot life time). This time is enough in that a delivered paste or powder of the zinc pigments may be either formulated at the aqueous based corrosion protection formulation manufacture site or may be preformulated first in an aqueous based zinc pigment slurry and then added to the corrosion protection formulation.

[0093] Method of coating the zinc pigment with additive:

[0094] A method of manufacture of the additive coated zinc pigments, especially a zinc flake, comprises a mixing step of the zinc pigments and the additive. Preferably such mixing step is conducted in a kneader or a mixer. The zinc pigments, preferably zinc flakes, are preferably mixed with a solvent to yield a paste prior to the coating step with the additive. Also, additional solvent may be added either to the additive or to the mixture of the zinc flakes and the additive to ensure a more homogeneous distribution. The mixing step may be conducted at room temperature, but also higher temperatures up to 60 °C, more preferably below of 50 °C may be chosen.

[0095] After the mixing step additional steps may follow like the addition of more solvent to a predetermined concentration of the coated zinc pigment. Also, the solvent or solvents may be removed by a drying step which can also be accompanied by applying a vacuum. Preferred temperatures for the drying step are in a range of 80 to 150 °C and more preferred in a range of 90 °C to 140 °C.

[0096] Finally, the solvent may be removed first and then exchanged for a different solvent when this product form might be more compatible with the envisaged corrosion protection formulation.

[0097] The coated zinc pigment may also be sieved to remove possible agglomerates although agglomeration was usually not observed during the coating treatment with the additive.

[0098] Coating composition for corrosion protection:

[0099] Another embodiment of this invention is a coating composition for corrosion protection comprising the zinc pigments coated with an additive as described before. This formulation may be a solvent based one but is preferably an aqueous based formulation.

[0100] Such aqueous based coating compositions are those whose solvent is water or a mixture of water and one or more organic solvents compatible with water. That is, the coating composition for corrosion protection preferably contains water as a solvent, and may further contain an organic solvent, preferably a hydrophilic organic solvent, in addition to water. In the case that the solvent is a mixture of water and an organic solvent (an aqueous solvent), the organic solvent to be used is preferably a hydrophilic organic solvent. The hydrophilic organic solvent may be the same as the hydrophilic organic solvent used when producing the additive coated zinc flake pigment and is contained in the resulting paste or composition.

[0101] Examples of the organic solvent that can be used in the coating composition for corrosion protection include, but are not limited to, glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol and tripropylene glycol; glycol ethers such as monomethyl ether, monoethyl ether, dimethyl ether and diethyl ether of the glycols; alcohols such as ethanol, propanol, isopropanol, butanol, isobutanol, tert-butanol and diacetone alcohol; and ketones such as acetone and methyl ethyl ketone. Among them, the organic solvent to be used is preferably glycols or glycol ethers. The organic solvent may be used singly or in combination of two or more. The water or aqueous solvent content of the corrosion coating composition of the present embodiment is not particularly limited, but generally it is preferably 20 wt.% or more, and more preferably 20 to 40 wt.%. In the case of an aqueous solvent, it is preferred that the water content of the aqueous solvent is 50 wt.% or more, and the organic solvent content of the aqueous solvent is 50 wt.% or less.

[0102] Generally, the coating composition for corrosion protection of the present embodiment further contains a binder. The binder may be any type, and any inorganic-based binder or organic-based binder resin can be used. The binder may be used singly or in combination of two or more.

[0103] Examples of the inorganic-based binder include, but are not limited to, a silane compound such as a silane-based coupling agent; silicates such as sodium silicate, potassium silicate and lithium silicate; metal alkoxide such as tetraethoxysilane, tetraethoxytitanium, tetraisopropoxytitanium, tetrapropoxyzirconium, triisopropoxyaluminum and dimethoxyzinc; and silicone resin. Examples of the silane-based coupling agent include, but are not limited to, vinylsilane-based coupling agents such as vinyltrimethoxysilane; acrylic silane-based coupling agents such as methacryloxypropyltrimethoxysilane; aminosilane-based coupling agents such as 3-amino-propyltrimethoxysilane; epoxysilane-based coupling agents such as p-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and y-glycidoxypropyltrimethoxysilane. Other examples of the inorganic-based binder that can be used are titanium-based coupling agents such as isopropyltriisostearoyl titanate; aluminum-based coupling agents such as acetoalkoxyaluminum diisopropylate; and zirconium-based coupling agents such as zirconium tributoxymonoacetylacetonate.

[0104] Among them, the inorganic-based binder is preferably a silane-based binder such as a silane-based coupling agent.

[0105] Examples of the organic-based binder resin include, but are not limited to, acrylic resins, epoxy resins, phenolic resins, polystyrene resins, polyurethane resins, oxazoline group-containing polymers, and polyvinylpyrrolidone.

[0106] The binder content of the coating composition for corrosion protection is not particularly limited and may be appropriately selected depending on the type of the binder or the like. When a silane-based binder is used, the silane-based binder content of the coating composition for corrosion protection is not particularly limited, but generally it is preferably 3 to 20 wt.%, and more preferably 4 to 16 wt.%, based on the total weight of the composition.

[0107] The coating composition for corrosion protection of the present embodiment contains the zinc pigments and preferably zinc flakes coated with the additive as described before. In addition, the coating composition for corrosion protection of the present embodiment may further contain another metal pigment.

[0108] Another metal pigment other than the zinc pigment may be coated at least partially with the additive of the present embodiment (hereinafter, also referred to as “the other metal pigment”) and may be any metal pigment. Examples thereof include, but are not limited to, a metal or metal alloy particle such as an aluminum or aluminum alloy particle, a manganese or manganese alloy particle, a nickel or nickel alloy particle, a titanium or titanium alloy particle, a tin or tin alloy particle, an iron or iron alloy particle, a cobalt or cobalt alloy particle, a tungsten or tungsten alloy particle, a vanadium or vanadium alloy particle, a molybdenum or molybdenum alloy particle, a tantalum or tantalum alloy particle, a niobium or niobium alloy particle, and a stainless steel particle. The other metal pigment may be used singly or in combinations of two or more. Preferably the other metal pigment has also a flake form.

[0109] In other preferred embodiments the other metal pigment may be stabilized against attack of water by a different additive or corrosion protection coating (like a silica or polymer coating) especially in case of an aluminum pigment. The metal or metal alloy particle, which is the other metal pigment, may have any shape, but generally they preferably have a substantially spherical shape or a flake-like shape, and more preferably a flake-like shape. Further, the other metal pigment may be at least partially surface-treated with, for example, silica, an aliphatic carboxylic acid, or the additive which was used to stabilize the zinc pigment.

[0110] In an exemplary aspect, it is preferred that the coating composition for corrosion protection further contains an aluminum or aluminum alloy particle in addition to the additive coated zinc pigment.

[0111] The zinc pigment content of the coating composition for corrosion protection (the amount of the zinc pigment of the present embodiment and optionally also the other metal pigment) is not particularly limited, but generally is preferably in a range of 10 to 90 wt.% and more preferably in a range of 20 to 40 wt.%, each based on the weight of the total coating composition. If the zinc pigment is composed mainly of zinc flakes the concentration is preferably limited to a range of 10 to 50 wt.%. and more preferably to a range of 15 to 40 wt.%.

[0112] When aluminum flake or aluminum alloy flake particle is used as the other metal pigment in combination with the zinc pigment, the ratio of the zinc pigment to the aluminum or aluminum alloy flake particle in the coating composition for corrosion protection is preferably 9:1 to 5:5 in terms of mass ratio.

[0113] The coating composition for corrosion protection may further contain a metal oxide pigment or an organic pigment. Examples of the metal oxide pigment include, but are not limited to, a manganese oxide particle, a molybdenum oxide particle, a tungsten oxide particle, a tin oxide particle, an antimony oxide particle, an iron oxide particle, an aluminum oxide particle, a zinc oxide particle, a magnesium oxide particle, a niobium oxide particle, a vanadium oxide particle, a tantalum oxide particle, a silica particle, a titania particle, a zirconia particle, a silica alumina particle, a silica titania particle, and a silica magnesia particle.

[0114] The organic pigment may be of any type. Examples thereof include, but are not limited to, p-naphthol pigments, p-oxynaphthoic pigments, pyrazolone-based pigments, acetoacetic acid allylide-based monoazo pigments, acetoacetic acid allylide-based disazo pigments, benzimidazolone-based monoazo pigments, isoindolinone-based pigments, styrene-based pigments, isoindoline-based pigments, and phthalocyanine-based pigments. The coating composition for corrosion protection may further contain a filler. Examples of such fillers are glass flakes, talc, mica or aerosil.

[0115] The coating composition for corrosion protection may further contain further electrically conducting particles which are not metals. Examples of such particles are graphite, graphene, or carbon nanotubes.

[0116] The coating composition for corrosion protection may contain, as appropriate, further additives such as a surfactant, a thickener, a repairing agent (inhibitor), a lubricant, a dispersant, a wetting agent, a leveling agent, a rheology control agent, a pH regulator, a pH stabilizer, a film forming agent, a stabilizer, a thixotropic agent, an anti-foaming agent, an ultraviolet absorber, a flame retardant, an antiseptic agent, an antistatic agent, and a colorant. The zinc pigment coated with the additive as described above is also excellent in dispersibility, and it is usually not necessary to add a dispersant. However, there are cases in which it is preferable to use a dispersant to stably disperse the other metal pigment or the additives.

[0117] There are cases in which adding a surfactant to the coating composition for corrosion protection can improve the adhesion or the leveling of the resulting preventive film. The surfactant may be of any type. Examples thereof include, but are not limited to, non-ionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl phenol ether, polyoxyethylene alkylamide, polyoxyethylene higher alcohol ether, polyoxyalkylene alkyl ether, polyoxyethylene polyoxypropylene glycol, polyethylene glycol fatty acid ester, glycerin fatty acid ester, propylene glycol fatty acid ester, alkyl glyceryl ether, sorbitan fatty acid ester, and polyoxyethylene sorbitan fatty acid ester; cationic-based surfactants such as mono-, di- or trialkylamine salts, alkyltrimethylammonium halide, dialkyldimetylammonium halide and alkyldimethylbenzylammonium chloride; and anionic-based surfactants such as dialkyl sulfosuccinates. Among them, the surfactant used is preferably a non-ionic surfactant. The surfactant may be used singly or in combinations of two or more.

[0118] The surfactant content of the coating composition for corrosion protection is not particularly limited, but generally it is preferably 0.01 to 10 wt.%, based on the total weight of the composition.

[0119] A thickener may also be added to the coating composition for corrosion protection for the purpose of adjusting the viscosity. The thickener may be of any type. Examples thereof include, but are not limited to, a cellulosic thickener such as an ether (a cellulose ether) of methylcellulose, hydroxymethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, ethylhydroxyethyl cellulose, methylethyl cellulose and hydroxypropyl cellulose; a cellulose nanofiber; a xanthan gum; a urethane-based thickener; an acrylic thickener; a modified clay; a fatty acid salt; and a fatty acid amido. Among them, the thickener used is preferably a cellulose ether. The thickener may be used singly or in combination of two or more.

[0120] The thickener content of the coating composition for corrosion protection is not particularly limited, but generally it is preferably 0.005 to 2 wt.%, based on the total weight of the composition.

[0121] A lubricant may also be added to the coating composition for corrosion protection for the purpose of adjusting the coefficient of friction of the surface of the rust preventive film obtained from the coating composition for corrosion protection. The lubricant may be of any type. Examples thereof include, but are not limited to, a wax such as polyolefin or modified polyolefin (polyethylene, modified polyethylene, polypropylene, modified polypropylene, etc.) or paraffin; a carnauba wax; fluorine resin; melamine cyanurate; or hexagonal boron nitride. The lubricant may be used singly or in combination of two or more.

[0122] The lubricant content of the coating composition for corrosion protection is not particularly limited and can be appropriately selected to obtain a desired surface frictional coefficient. Generally, it is preferably 20 wt.% or less.

[0123] The coating composition for corrosion protection can be produced, by a known method commonly used, by uniformly stirring and mixing the zinc pigment coated with the additive or a paste or composition containing the zinc pigment coated with the additive with paint components such as water and / or the organic solvent, the binder, etc.

[0124] The coating composition for corrosion protection may be a 1 K- or a 2K-system. In case of a 2K system the zinc flakes may be formulated either to the binder component or to the hardener component.

[0125] Preferred embodiments include aqueous based coating composition for corrosion protection wherein the formulation is suitable for heavy duty corrosion protection applications, architectural & construction applications, electricity & energy, wind power & offshore applications, agriculture construction earthmover (ACE) and truck & trailer applications. Preventive Film and an Article with a Preventive Film

[0126] A preventive film on an article is obtained by drying or heat-treating the coating composition for corrosion protection described above. An article with a preventive film has, on a surface thereof, a preventive film obtained by drying or heat-treating the coating composition for corrosion protection described above; and is obtained by, for example, by applying the coating composition for corrosion protection to an article to be coated and drying or heat-treating the applied preventive coating composition.

[0127] The coating composition for corrosion protection can be applied to an article which is composed of any metal material or alloy material. Examples of the metal material and the alloy material include, but are not limited to aluminum, aluminum alloy, iron, iron alloy, carbon steel, alloy steel, and stainless steel. The coating composition for corrosion protection can also be applied to a metal material or an alloy material whose surface has been subjected to plating; chemical conversion treatment such as oxidation, nitridation and carbonization; and dry plating. Among them, the coating composition for corrosion protection can be suitably applied to an article to be coated that contains an iron or an iron alloy, or an article to be coated that has, on its surface, a film or layer containing iron or an iron alloy, and an excellent effect of improving the corrosion resistance can be obtained. Incidentally, a coating target or an article to be coated may be a raw material (a metal material or an alloy material itself), an intermediate product, a final product, or the like without particular limitation.

[0128] The coating composition for corrosion protection may be applied to an article to be coated by any known method. The coating composition for corrosion protection can be applied using a roller, a doctor blade, a bar coater, a brush, or the like. Further, the application conditions may be appropriately selected without particular limitation.

[0129] The preventive film is formed by applying the coating composition for corrosion protection of the present embodiment to an article to be coated and then drying or heat-treating it. Although the method and conditions for the drying and heat-treating may be appropriately selected, it is generally preferred to heat the coating composition for corrosion protection applied to an article to be coated at a temperature of 120 to 400 °C and more preferably 130 to 380 °C to remove the solvent and form the preventive film. This heating may be performed in any known method such as a convection heating method, an infrared heating method, or an induction heating method. The conditions of the heat treatment such as the time period and atmosphere of the heat treatment may also be appropriately selected without particular limitation. For example, the heat treatment may be performed in the atmosphere or may be performed in an inert gas such as nitrogen gas.

[0130] An article to be coated may be subjected to a treatment such as degreasing, water washing or the like as appropriate before the coating composition for corrosion protection is applied to the article to be coated. Such degreasing and water washing treatments can be performed by any known methods. The degreasing and water washing treatments may be appropriately selected and may be solvent degreasing using a hydrocarbon-based degreasing agent or the like, water washing treatment using an alkaline aqueous degreasing agent or the like, or washing treatment using supercritical water or the like, for example.

[0131] The application amount of the coating composition for corrosion protection is not particularly limited, but generally it is applied in such an amount that the average thickness of the preventive film after drying is preferably 1 to 200 pm, more preferably 4 to 100 pm. In terms of the amount of zinc after drying, the coating composition for corrosion protection is applied in such an amount that the zinc content of the preventive film after drying is preferably 3 to 200 g / m2, and more preferably 20 to 120 g / m2.

[0132] A further first aspect is directed to an aqueous based coating composition for corrosion protection comprising the zinc pigments according to any of the disclosed embodiments described in this invention and especially in claims 1 to 14.

[0133] A further second aspect is directed to an aqueous based coating composition for corrosion protection according to the first aspect, wherein the formulation is suitable for heavy duty corrosion applications, protection applications, architectural & construction applications, electricity & energy, wind power & offshore applications, agriculture construction earthmover (ACE) and truck & trailer applications.

[0134] A further third aspect is directed to a preventive film on an article which has been manufactured by applying the aqueous based coating composition of aspects 1 or 2 to an article followed by drying or heat treatment. EXAMPLES:

[0135] A Coating Examples:

[0136] Example 1:

[0137] 300.00 g zinc flakes (commercially available Zink GTT, manufactured by ECKART Suisse with dso = 13 pm, obtained by dry milling of zinc powder with stearic acid as grinding aid) were placed in a kneader mixer. A solution of 4.00 g of Additol XL 250 (active content: about 55 wt.% additive from Allnex Germany GmbH) in 25.00 g white spirit was added. The zinc pigment with the stabilizer solution was mixed at 130 °C under reduced pressure (200 mbar) until all solvent was removed. Afterwards the kneader mixer was cooled to 40 °C and 29.33 g methoxy propanol was added. After homogenization in the kneader mixer, the stabilized zinc paste was removed.

[0138] Example 2:

[0139] A solution of 7.00 g Additol XL 250 (Allnex Germany GmbH) in 25.00 g of white spirit was prepared by stirring the two components for 30 minutes. The solution was added to 300.00 g zinc flakes (Zink GTT) in a kneader mixer. The kneader mixer was heated to 130 °C and the solvent was removed under reduced pressure (200 mbar). Afterwards, the kneader mixer was cooled to 40 °C and methoxy propanol was added to make a composition having a solid content of 90% (26.33 g). The paste was homogenized for 30 minutes and the stabilized zinc paste was removed from the kneader mixer.

[0140] Comparative Example 1: Commercially available uncoated zinc GTT flakes (Eckart GmbH).

[0141] An analysis of additive Additol XL 250 using GPC,1D NMR and 2D NMR-spectroscopy (1H,13C,31P cores) and LC-MS (liquid chromatography-mass spectroscopy) proved that this additive was to a main part composed of an oligomeric ester of ricinoleic acid with smaller parts of ester of corresponding linolic acid which were partly phosphatized. As alcoholic component a derivative of Bisphenol A was present in lesser amounts than ricinoleic acid. Table 1 gives an overview of the parameters corresponding to generic formulas (la), (lb) and (Ila). The additive contained ethanol as solvent and the oligomeric polyester was neutralized with dimethyl ethanol amine. Linoleic acid is a common companion of ricinoleic acid. Table 1: Correlation of analytical analysis of additive with respect to parameters of generic formulas

[0142] Chemical moiety Generic moiety

[0143] formula

[0144] Oligomeric ester of (la) R1: alkyl with 6 C-atoms

[0145] ricinoleic acid, partially R2: aliphatic moiety (alkenyl) with 10 C-atoms phosphatized A: O-PO(OR3)2, -OR3or -O-CO-R4

[0146] R3: H, protonated amine

[0147] x = 1 to 6, maximum of about 2

[0148] Partially ester oligomers (lb) R4: aliphatic moiety with 17 C-atoms (origin involving linoleic acid from linoleic acid)

[0149] Oligomeric ester of (Ha) R5: bisphenol A bis(2-hydroxypropyl) derivative ricinoleic acid with bis(Dianol 33)

[0150] phenol derivate, partially R6: OH or O-PO(OR3)2

[0151] phosphatized B: O-PO(OR3)2, -OR3, -O-CO-R4

[0152] Ester of linoleic acid with (Hb) D: OH or O-PO(OR3)2

[0153] bisphenol A bis(2- hydroxypropyl) derivative

[0154]

[0155] B Testing Methods and Results:

[0156] B1 Dispersibility:

[0157] A water dilutable epoxy binder (EPI-REZ Resin 6520-WH53, manufactured by Allnex) was diluted with a water / methoxy propanol mixture to a viscosity of 23 sec DIN #4 cup. The diluted epoxy binder was poured into a plastic cup stirred at 3000 rps while adding and homogenizing the zinc flakes over 20 minutes. The mixing ratio was selected that the diluted epoxy binder contained 30% by weight of the zinc flakes, based on the total weight of this dispersion. After homogenization, a hardener was added (Epikure Curing Agent 8538-Y-68) to allow curing.

[0158] These zinc pigmented varnishes were applied with a 100 pm rod onto a transparent PE foil. The film was cured at 80°C for 30 minutes to a completely cured film. The cured film was put onto a lamp allowing visual assessment of uniformity and possible grains in the dry film. The optical appearance was rated follows:

[0159] 1 : uniform, even film; no grains and lumps, a perfect film 2: slight surface roughness; few grains detectable (still acceptable)

[0160] 3: surface was rough; larger grains detectable with fingers and high number of grains visible in transmitted light (not acceptable)

[0161] 4: uneven film; lots of grains visible uniformly on application: rough and uneven surface.

[0162] The inventive Examples 1 and 2 were rated as 1 while the comparative Example 1 was rated as 3.

[0163] Furthermore in the aforementioned test set-up the time of mixing was varied to achieve a uniform film with rating 1. Duration of mixing for a film with rating 1 was determined to be 30 minutes with a stabilized zinc flake pigment (examples 1 and 2) and one hour for an unstabilized zinc flake (comparative example 1).

[0164] B2 Gassing stability test in a binder-free slurry:

[0165] Hydrogen gas evolution was determined using an aqueous solution of 1.9 g Laponite RD and 28.2 g of water (binder free slurry; no settlement of specifically heavy zinc pigment) as an anti-settling slurry. The anti-settling slurry was left for 48 hours to allow complete wetting. After 48 hours 100 g of a 1 :1 mix of zinc flake: methoxy propanol slurry was blended into the Laponite slurry. 100 g of this composition was placed in an Erlenmeyer flask, which was sealed with a double chamber glass fixture.

[0166] The test was conducted at room temperature and the gas evolution was determined over time by measuring the volume of displaced amount of water in the upper chamber. When the gas evolution was below 20 ml after eight days the gassing stability was assumed to be enough to be used as a freshly mixed zinc flake formulation at, for example, the construction site of final use. Table 2: Gas evolution results of gassing test:

[0167] Sample Gas evolution overtime

[0168] 1h 2h 3h 4h 5h 6h 7h 8h 24h Comparative Zn 1400 0 0 10 16 20+

[0169] Example 1

[0170] Example 1 VP 72310 / G 0 0 0 0 0,5 3 7.5 10.5 20+

[0171] reproduction

[0172] Example 2 VP 72313 / G 0 0 0 0 1 4 8.5 11.5 20+

[0173]

[0174] In this test the unstabilized zinc flake (comparative example 1) produced high amounts of hydrogen gas very fast. The stabilized zinc flakes (examples 1 and 2) generated same amount of hydrogen in longer period of time. After eight days the amount was clearly below 20 and therefore a use in aqueous corrosion formulations seems to be reasonable.

[0175] B3 Salt spray test in a 2K aqueous epoxy / amine system:

[0176] A water dilutable epoxy primer was formulated according to the following formulation: Table 3: Preparation of spray application coating formulation

[0177] PVC total 36.6 PVC Zinc 12.7 PVC Filler 23.8 Grind formulation

[0178] (Component A)

[0179] EPI-REZ Resin 6520- . _ _

[0180] Start then add while stirring: 22.36 1 WH53

[0181] 2 Disperbyk 192 0.44 3 demin. Water 17.89 4 Heucophos ZCP plus 2.51 5 Micro Talcum AT extra 11.86 6 Blanc fixe micro 4.48 7 By k 011 30min 2500 rotations / min 0.54 8 Bentone EW 0.54 9 Halox Flash-X 150 finally stir lOmin 1000 rotations / min 0.54 total 61.16 Allow 1 day resting

[0182] Zinc flake pre mix

[0183] Component B

[0184] Epikure Curing Agent Start with and ad one after the

[0185] 1 8538-Y-68 Other 4.84 Solvent l-Methoxy-2

[0186] 2 Propanol) 3.35 3 Solvent 2 Propanol 3.35 3 Disperbyk 142 Stir 1000 r / min 2min 0.22 4 Stabilized Zinc Flake Add while stirring 26.00 5 Sylosiv A3 30min 2500 r / min 0.56 6 BykOll 0.32 7 Bentone EW 5min at 1000 r / min 0.22 Total 38.86 allow 1 day rest

[0187] Mix component A and B together after rest time for 1000 r / min 5 min

[0188]

[0189] For the spray application the primer is diluted with water down to 13 seconds in a 13 DIN #6 cup. The primer was sprayed on sand blasted steel SA 2.5 panels at 80 pm dry film thickness, cured at room temperature for two hours and baked at 120 °C for 30 minutes. No top coating was applied here. After one week a scratch was applied, while the sides and back side of the panel were sealed and the panel was exposed to a salt spray test according to ISO 9227.

[0190] After 1400 hours exposure the following results were obtained:

[0191] adhesion according to ISO 4624: 5.0 MPa

[0192] no blistering occurred according to ISO 4628-2

[0193] cross cut according to ISO 2409: GT 0

[0194] creep at scribe according to ISO 12944-6: 2 mm

[0195] These results are acceptable for an aqueous based corrosion system with regard to the demands of coating industry.

Claims

Claims:

1. A zinc pigment or zinc alloy pigment suitable for aqueous based corrosion paint formulations, wherein the zinc flake is at least partially coated with an additive which is based on an oligomeric polyester of fatty acid which is at least partially phosphated or phosphonated and comprises at least a first polyester component or a mixture of different components being represented by the following formula (la):R1-CH-(O-CO-R2-CH-)xA (la)R2-COOR3R1and optionally also a second polyester component or a mixture of different components being represented by the following formula (lb):R4-COO-CH-(O-CO-R2-CH-)yA (lb)i , Lwherein: R1is an alkyl moiety from 4 to 10 C-atoms,R2is an aliphatic moiety from 8 to 14 C-atoms,A is a group independently chosen from any member of the group consisting of - O-PO(OR3)2, -PO(OR3)2, -OR3or-O-CO-R4,R3is independently H, methyl or ethyl or protonated amines,R4is an aliphatic moiety having 15 to 21 C-atoms,x is an integer in the range of 1 to 10and y is an integer in the range of 0 to 10 with the proviso, that for y=0 A cannot be -O-CO-R4.

2. The zinc pigment according to claim 1 , wherein the additive further comprises a third component of formula (Ila):R1-CH-R2-CO-O-R5-B, (Ila)and optionally also of formula (lib):R4-CO-O-R5-D(lib)wherein O-R5represents a monomer moiety comprising a bisphenol or bisphenol ether moiety,wherein R6is independently any of OH, O-PO(OR3)2, PO(OR3)2,O-CO-R2-CH-OR3or O-CO-R4andwherein group B is any of group A or -CO-R2-CH-R1and wherein group D is any of the group consisting of OH, O-PO(OR3)2, PO(OR3)2 or O-CO-R4.

3. The zinc pigment according to claims 1 or 2, wherein R1is an alkyl group from 6 to 8 C-atoms.

4. Zinc pigment according to any of the preceding claims, wherein R2is an aliphatic moiety from 10 to 12 C-atoms.

5. The zinc pigment according to any of the preceding claims, wherein R3is independently H, ethyl or a protonated amine.

6. The zinc pigment according to any of the preceding claims, wherein R4comprises 16 to 20 C-atoms.

7. The zinc pigment according to any of the preceding claims, wherein x is in a range of 1 to 6.

8. The zinc pigment according to claim 2, wherein the moiety O-R5is a bisphenol A bis(2-hydroxypropyl) moiety.

9. The zinc pigment according to any of the preceding claims, wherein at least 2.5 mol-% and preferably at least 3.4 mol-% of all of the group A, and optionally also of groups B and D being part of the oligomeric species of the additive as represented by formulas (la), (lb), and optionally also additionally by formulas (Ila) or (lib) contain a phosphate group.

10. The zinc pigment according to any of the preceding claims, wherein the additive is directly bonded on the surface of the zinc pigment.

11. The zinc pigment according to any of the preceding claims, wherein the average molecular weight of the is in a range of 500 to 1000 g / mol, as determined by GPC (gel permeation chromatography).

12. The zinc pigment according to any of the preceding claims, wherein the amount of the additive is in a range of 0.3 to 5.0 wt.% referred to the weight of the zinc pigment.

13. The zinc pigment according to any of the preceding claims, wherein the zinc pigments contain at least 50 wt.% of zinc flake and preferably contains zinc flakes in a ratio of 98 wt.% to 100 wt.%.

14. The zinc pigment according to claim 13, wherein the zinc pigment are zinc flakes.

15. Method of manufacture the zinc pigment coated with the additive according to any of claims 1 to 14, comprising a mixing step of zinc pigments and the additive.

16. Aqueous based coating composition for corrosion protection comprising the zinc pigments according to any of claims 1 to 14.

17. Aqueous based coating composition for corrosion protection according to claim 16, wherein the formulation is suitable for heavy duty corrosion applications, protection applications, architectural & construction applications, electricity & energy, wind power & offshore applications, agriculture construction earthmover (ACE) and truck & trailer applications.

18. Preventive film on an article which has been manufactured by applying the aqueous based coating composition of claims 16 or 17 to an article followed by drying or heat treatment.

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