DE102007003761B4 - Coated substrates with heterogeneous surface properties - Google Patents

Abstract

A coated substrate, wherein the substrate is an aircraft structure and comprises at least one connecting element or at least one connecting element, wherein the substrate further comprises at least one connecting element in contact with at least one further substrate body, wherein the further substrate body is painted, wherein the coating is a gap between the coating element and the further substrate body is covered, wherein the coating is applied both on the connecting element and on the paint of the further substrate body, wherein the coated substrate is obtainable by a method for producing a coating on a substrate, comprising the following steps: providing a Substrate, - Provision or production of an incompletely cured coating material, - Hardening or hardening of the coating material and - At least partially applying the coating material to the Substrate before or during curing, and wherein the coating material that can be produced using the following components, or multicomponent system for producing a coating comprises or consists of the following components: (A) 15-50 mol% of one or more silicon organic compounds of the formula (I) Ra 4-nSiXa n (I), wherein: each Xa is independently of any other Xa a hydrolyzable radical; each Ra is independently of any other Ra a nonhydrolyzable radical; n is 2, 3 or 4; (B) 30-70 mol% of one or more organosilicon compounds of formula (II) wherein: each Xb is independently of any other Xb a hydrolyzable group; Rb is a non-hydrolyzable radical without epoxide function, without acryloxy function, without methacryloxy function and without isocyanate function; each Yb is independently of any other Yb a non-hydrolyzable radical having a crosslinkable function selected from the group consisting of epoxide, acryloxy, methacryloxy and isocyanate p is 2 or 3; q is 1 or 2; the sum of p and q is less than or equal to 4; (C) 2-25 mol% of one or more cross-linking agents for the crosslinkable function of the Yb radical; ...

Description

The present invention relates to substrates coated with coating materials, the substrate being an aircraft structure consisting of at least one connecting element or comprising at least one connecting element. The substrate comprises a further substrate which is in contact with the at least one connecting element.

The present invention is used for coating aircraft structures, in particular composite structural components with at least one rivet (or a corresponding other connecting element).

The invention will be described below with reference to aircraft construction and the structural components with rivets used therein.

In aircraft, structural components are regularly connected by fasteners (rivets), such as stringer and frame with the planking. The connections made then take over static and dynamic loads. The metal fasteners (rivets) usually used in aircraft construction have hitherto been protected against corrosion by expensive protective systems. The protection systems are to prevent corrosion on both the structural components and on the connecting elements. Usually, the protection systems consist of two, three or four layers, which are applied in several operations, for example by spraying, rolling and / or brushing or galvanic. The multi-layer systems used so far regularly comprise an oxide layer (CAA) or a conversion coating, a primer layer applied thereon and, if appropriate, a topcoat arranged on the primer layer (it being also possible to provide a sealant between primer layer and topcoat).

A disadvantage of the protection systems hitherto commonly used are, in particular, the multiplicity of manufacturing process steps, the amount of solvent immission, the paint waste quantities and / or the high weight of the coated substrates.

These parameters require improvement for economic and environmental reasons. However, the search for alternative, a reduction of production costs, the solvent immission, the Lackabfallmengen and / or the weight-permitting protective systems for aircraft structures, in addition to (composite) structural components also comprise at least one rivet, but is difficult due to the high technical requirements for such protection systems ,

First, they must provide an effective barrier against a variety of media to which they are exposed. In addition to water in its various states of aggregation in particular corrosion-promoting electrolytes such. B. NaCl solution, aggressive Phosphatester hydraulic fluids such as Skydrol ^® (Solutia Inc.) and the like. A closed film formed by such a protection system must be an effective diffusion barrier and must not be attacked by the media acting on it.

On the other hand, the adhesion of the protection system to the substrate (eg structural components with rivets) must be ensured even under mechanical stress. In the maintenance of aircraft, the coated, studded structural components are claimed by walking and working. In flight operations there are often due to high compressive forces and tensile stresses and strong temperature fluctuations on extreme mechanical stress. These are particularly high at interfaces where different materials with different thermal expansion coefficients abut each other. In order to withstand the stresses at the respective interfaces, a high elasticity of the protection systems is required.

A further complicating factor is that the protective systems must not only adhere effectively to a single but to different surfaces. In aircraft used fasteners (especially rivets) are usually made of aluminum, titanium or steel, while the surrounding structural components are regularly painted.

Recently, alternative coating materials based on the sol-gel principle have been developed. However, there are so far no special coating material (and not functioning according to the sol-gel principle multi-component system for producing a coating) on aircraft structures, which also comprise at least one rivet in addition to a structural component, the coating also under Operating conditions good and safe on the adjacent different surfaces (rivet, structural component) adheres and at the same time offers good corrosion protection.

• US 2003/0024432 A1 betreffend „Corrosion inhibiting Sol-Gel coatings for metal alloys”.
• US 5,175,027 betreffend ”Ultra-thin, uniform sol-gel coatings”.
• US 5,206,285 betreffend ”Aqueous coating of silane precursor from epoxy and amino trialkoxysilanes”.
• US 5,939,197 A betreffend ein „Sol-Gel coated metal”.
• US 5,958,578 A betreffend ein „Hybrid laminate having improved metal-to-resin adhesion”.
• US 5,866,652 A betreffend „Chromate-free protective coatings”.
• US 6,037,060 betreffend ein ”Sol for bonding epoxies to aluminium or titanium alloys”.
• DE 198 13 709 A1 betreffend ein „Verfahren zum Schutz eines metallischen Substrats vor Korrosion”.
• DE 43 38 361 A1 (entspricht EP 0 728 164 B1 ) betreffend ein „Verfahren zur Herstellung von Zusammensetzungen auf Basis von Epoxidgruppen-haltigen Silanen”.
• DE 43 03 570 A1 ( EP 0 610 831 B1 ) betreffend ein „Beschichtungsmaterial und Verfahren zur Herstellung funktioneller Beschichtungen”.
• DE 696 21 941 T2 betreffend „nichtchromatische Korrosionsinhibitoren für Aluminiumlegierungen”.
• EP 0 358 338 B1 betreffend ein „Method and composition for surface treatment”.
• EP 1 493 843 A1 betreffend eine 'Coated metallic component”. (Entspricht WO 2005/003407 A1 ).

Please refer to the following documents:

• US 2003/0024432 A1 concerning "corrosion inhibiting sol-gel coatings for metal alloys".
• US 5,175,027 concerning "Ultra-thin, uniform sol-gel coatings".
• US 5,206,285 relating to "Aqueous coating of silane precursors of epoxy and amino trialkoxysilanes".
• US 5,939,197 A concerning a "sol-gel coated metal".
• US 5,958,578 A concerning a "hybrid laminate having improved metal-to-resin adhesion".
• US 5,866,652 A concerning chromate-free protective coatings.
• US 6,037,060 concerning a sol for bonding epoxies to aluminum or titanium alloys.
• DE 198 13 709 A1 concerning a "Method for Protecting a Metallic Substrate from Corrosion".
• DE 43 38 361 A1 (equivalent to EP 0 728 164 B1 ) concerning a "process for the preparation of compositions based on epoxide group-containing silanes".
• DE 43 03 570 A1 ( EP 0 610 831 B1 ) concerning a "coating material and process for producing functional coatings".
• DE 696 21 941 T2 concerning "non-chromatic corrosion inhibitors for aluminum alloys".
• EP 0 358 338 B1 concerning a method and composition for surface treatment.
• EP 1 493 843 A1 concerning a coated metallic component. (Equivalent WO 2005/003407 A1 ).

Other sol-gel based coating compositions are disclosed in the documents DE 199 52 040 A1 . DE 198 57 316 A1 . DE 103 20 765 A1 and US 2004-0099845 A1 described.

From none of the cited documents does a sol-gel-based coating material or multicomponent system result for the production of a coating, which after application to an aircraft structural component with at least one rivet simultaneously a high elasticity, a good barrier effect and effective adhesion to different Materials guaranteed.

It was the primary object of the present invention to provide a coating on aircraft structural components based on a corresponding sol-gel coating material.

• (A) 15–50 mol% an einer oder mehreren silicium-organischen Verbindungen der Formel (I) R^a _4-nSiX^a _n (I), wobei gilt: jedes X^a ist unabhängig von jedem anderen X^a ein hydrolysierbarer Rest; jedes R^a ist unabhängig von jedem anderen R^a ein nicht hydrolysierbarer Rest; n ist 2, 3 oder 4; (Hinweis: Zur Komponente (A) werden lediglich Verbindungen gezählt, die nicht als Bestandteil der Komponente (B) aufgefasst werden können; sofern eine Verbindung der Formel (I) vorhanden ist, die gleichzeitig auch eine Verbindung der Formel (II) ist, wird diese zur Komponente (B) gezählt.)
• (B) 30–70 mol% an einer oder mehreren silicium-organischen Verbindungen der Formel (II)
  
  wobei gilt: jedes X^b ist unabhängig von jedem anderen X^b ein hydrolysierbarer Rest; R^b ist ein nicht hydrolysierbarer Rest ohne Epoxidfunktion, ohne Acryloxyfunktion, ohne Methacryloxyfunktion und ohne Isocyanatfunktion; jedes Y^b ist unabhängig von jedem anderen Y^b ein nicht hydrolysierbarer Rest mit einer vernetzbaren Funktion ausgewählt aus der Gruppe bestehend aus Epoxid, Acryloxy, Methacryloxy und Isocyanat; p ist 2 oder 3; q ist 1 oder 2; die Summe aus p und q ist kleiner als oder gleich 4;
• (C) 2–25 mol% an einem oder mehreren Vernetzungsmitteln für die vernetzbare Funktion des Restes Y^b; (Hinweis: Zur Komponente (C) werden lediglich solche Vernetzungsmittel gezählt, die nicht als Bestandteil der Komponente (F) oder einer anderen Komponente aufgefasst werden können.)
• (D) 0–40 mol% an einer oder mehreren Organo-Zirconium-, Organo-Titan- oder Organo-Aluminium-Verbindungen mit hydrolysierbaren organischen Resten, zur Ausbildung von kovalenten Brücken zwischen Siliciumatomen und Metallatomen eines metallischen Substrats;
• (E) vorzugsweise einem oder mehreren Hydrolysekatalysatoren;
• (F) einem oder mehreren vernetzbaren Präpolymeren ausgewählt aus der Gruppe bestehend aus Epoxy-Harzen und Epoxy-Siloxan-Harzen und deren Mischungen, wobei das bzw. eines, mehrere oder sämtliche der Präpolymere ein Epoxy-Äquivalentgewicht von mindestens 200 aufweist, wobei der Anteil an gegebenenfalls vorhandenen Präpolymeren mit einem Epoxy-Äquivalentgewicht von unter 200 bei maximal 5 Gew.-% liegt, bezogen auf das Gesamtgewicht der Komponenten (A), (B), (C) und (D), wobei der Anteil von gegebenenfalls vorhandenen Präpolymeren mit einem Epoxy-Äquivalentgewicht von unter 200 nicht größer ist als der Anteil von Präpolymeren mit einem Epoxy-Äquivalentgewicht von mindestens 200; (Hinweis: Komponente (F) kann auch Präpolymere umfassen, die die vernetzbare Funktion des nicht hydrolysierbaren Rests Y^b einer Verbindung der Formel (II) vernetzen können) sowie gegebenenfalls
• (G) einem oder mehreren Korrosionsinhibitoren, ausgewählt aus der Gruppe bestehend aus anorganischen und organischen Korrosionsinhibitoren; sowie gegebenenfalls
• (H) einer oder mehreren Verbindungen zur Reduzierung der Reaktivität von Komponente (D); wobei sich die Molprozent-Angaben auf die Gesamtstoffmenge der Komponenten (A), (B), (C) und (D) beziehen, mit der Maßgabe, dass n und die Summe aus p + q nicht gleichzeitig jeweils 4 sind.

According to the invention, the stated object is achieved by a structural component that is coated with a sol-gel coating material which can be produced using the following components (ie by their chemical reaction) comprising or consisting of the following components:

• (A) 15-50 mol% of one or more organosilicon compounds of the formula (I) R ^a _4-n SiX ^a _n (I), where: each X ^a is independently of any other X ^a a hydrolyzable group; each R ^a is independently of any other R ^a is a non-hydrolysable radical; n is 2, 3 or 4; (Note: Component (A) only includes compounds that can not be considered as part of component (B), provided that a compound of formula (I) is present which is also a compound of formula (II) these are counted as component (B).)
• (B) 30-70 mol% of one or more organosilicon compounds of the formula (II)
  
  wherein: each X ^b is a hydrolyzable group independently of any other X ^b ; R ^b is a non-hydrolyzable radical without epoxide function, without acryloxy function, without methacryloxy function and without isocyanate function; each Y ^b is independently of any other Y ^b a non-hydrolyzable radical having a crosslinkable function selected from the group consisting of epoxide, acryloxy, methacryloxy and isocyanate; p is 2 or 3; q is 1 or 2; the sum of p and q is less than or equal to 4;
• (C) 2-25 mol% of one or more crosslinking agents for the crosslinkable function of the radical Y ^b ; (Note: Component (C) only includes those crosslinking agents that can not be considered as part of component (F) or any other component.)
• (D) 0-40 mol% of one or more organo-zirconium, organo-titanium or organo-aluminum compounds having hydrolyzable organic radicals, to form covalent bridges between silicon atoms and metal atoms of a metallic substrate;
• (E) preferably one or more hydrolysis catalysts;
• (F) one or more crosslinkable prepolymers selected from the group consisting of epoxy resins and epoxy siloxane resins and mixtures thereof, the one or more or all of the prepolymers having an epoxy equivalent weight of at least 200, wherein the proportion optionally present prepolymers having an epoxy equivalent weight of less than 200 at a maximum of 5 wt .-%, based on the total weight of components (A), (B), (C) and (D), wherein the proportion of optionally present prepolymers having an epoxy equivalent weight of less than 200 is not greater than the proportion of prepolymers having an epoxy equivalent weight of at least 200; (Note: Component (F) may also include prepolymers that can crosslink the crosslinkable function of the nonhydrolyzable group Y ^{b of} a compound of formula (II)) and optionally
• (G) one or more corrosion inhibitors selected from the group consisting of inorganic and organic corrosion inhibitors; and optionally
• (H) one or more compounds to reduce the reactivity of component (D); wherein the mole percentages are based on the total amount of the components (A), (B), (C) and (D), provided that n and the sum of p + q are not all 4 simultaneously.

By the term "crosslinkable" is meant the ability to contribute in a manner to the formation of a covalent network that is not based on the formation of Si-O-Si linkages.

The term "curing" as used herein refers to the formation of a covalent network and includes several processes: the formation of Si-O-Si linkages as well as all processes that contribute to the formation of a covalent network in a manner that does not based on the formation of Si-O-Si linkages.

Hereinafter, the components (A) to (H) will be described in more detail.

(A) Silicon organic compound of the formula (I)

The organosilicon compounds of the formula (I) contribute to the formation of the Si-O network in the coating materials or multicomponent systems by hydrolysis and condensation and may contain 2, 3 or 4, preferably 2 or 3 and particularly preferably 3 hydrolyzable radicals X ^a , Depending on the number of hydrolyzable radicals X ^a , the compounds of the formula (I) optionally also contain nonhydrolyzable radicals R ^a .

Preference is given to coating materials or multicomponent systems for which the following applies in the compound or compound of the formula (I) of component (A):
X ^a is selected from the group consisting of F, Cl, Br, I, OH, alkoxy, aryloxy, acyloxy, alkylcarbonyl and alkoxycarbonyl; and or
R ^a is selected from the group consisting of alkyl, alkenyl, alkynyl, aryl, arylalkyl, alkylaryl, arylalkenyl, alkenylaryl, arylalkynyl, alkynylaryl and alkylalkenyl;
where R ^a is that optionally an H is replaced by a substituent.

Particular preference is given to coating materials or multicomponent systems for which the following applies in the or a compound of the formula (I) of component (A):
X ^a is selected from the group consisting of Cl, Br, OH, alkoxy having 1 to 22 C atoms, aryloxy having 6 to 10 C atoms, acyloxy having 1 to 22 C atoms and alkylcarbonyl having 2 C atoms; and or
R ^a is selected from the group consisting of alkyl having 1 to 20 carbon atoms, alkenyl having 2 to 20 carbon atoms, alkynyl having 2 to 4 carbon atoms; Aryl of 6 to 10 C atoms; Alkylaryl of 7 to 28 carbon atoms, alkylalkenyl of 3 to 22 carbon atoms and alkenylaryl of 8 to 28 carbon atoms;
where R ^a is that optionally an H is replaced by a substituent.

Preferably, the optional substituent on the radical R ^{a is} selected from the group consisting of halogen and alkoxy.

Examples of preferred compounds of formula (I) are tetraethylorthosilicate, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, propyltriethoxysilane, n-propyltrimethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, n-hexyltrimethoxysilane, n-octyltrimethoxysilane, isooctyltrimethoxysilane, n-octadecyltrimethoxysilane, cyclohexylmethyldimethoxysilane, vinyltriethoxysilane, Vinylethyldichlorosilane, vinylmethyldiethoxysilane and vinyltriacetoxysilane.

In order to adjust the elasticity (flexibility) of the coating (the cured coating material), the presence of non-crosslinkable radicals R ^{a is} preferred.

Very particular preference is given to coating materials or multicomponent systems in which, in the compound or compound of the formula (I) of component (A), n = 2 or 3 and R ^{a is} a non-crosslinkable radical.

Particular preference is given to coating materials or multicomponent systems in which the compound or compounds of the formula (I) of component (A):
X ^a is methoxy or ethoxy, preferably methoxy;
R ^a is selected from the group consisting of methyl, ethyl, propyl, hexadecyl, (cyclohexyl) methyl, (n-octadecyl), isooctyl, dicyclopentyl and phenyl; and
n = 2 or 3.

Most preferred are coating materials or multicomponent systems containing as the or a compound of formula (I) of component (A) phenyltrimethoxysilane (particularly preferred), isooctyltrimethoxysilane, n-octadecyltrimethoxysilane or cyclohexylmethyldimethoxysilane.

Component (A) is preferably used in an amount of 15-50 mol%, preferably 20-40 mol%, based on the total amount of the components (A), (B), (C) and (D).

(B) Silicon organic compound of the formula (II)

The organosilicon compounds of the formula (II) also contribute to the formation of covalent bonds in the coating materials or multicomponent systems. On the one hand this is done by hydrolysis and condensation and thus by formation of the Si-O network. For this purpose, the compounds of the formula (II) contain 2 or 3, preferably 3 hydrolyzable radicals X ^b . On the other hand, the formation of covalent bonds by means of the crosslinkable functions of the non-hydrolysable radicals Y ^{b occurs} . This increases the network density and enhances the diffusion barrier and the scratch resistance of the layer. The compounds of the formula (II) comprise 1 or 2, preferably 1, nonhydrolyzable radicals Y ^b having a crosslinkable function selected from the group consisting of epoxide, acryloxy, methacryloxy and isocyanate. Depending on the number of radicals X ^b and Y ^{b are} the compounds of formula (II) optionally also contain non-hydrolysable radicals R ^b without epoxide without Acryloxyfunktion without Methacryloxyfunktion and without isocyanate.

Preference is given to coating materials or multicomponent systems for which the following applies in the or a compound of the formula (II) of component (B):
X ^b is selected from the group consisting of F, Cl, Br, I, OH, alkoxy, aryloxy, acyloxy, alkylcarbonyl and alkoxycarbonyl; and or
R ^b is selected from the group consisting of alkyl, alkenyl, alkynyl, aryl, arylalkyl, alkylaryl, arylalkenyl, alkenylaryl, arylalkynyl, alkynylaryl and alkylalkenyl;
where R ^b is that optionally an H is replaced by a substituent.

Particular preference is given to coating materials or multicomponent systems in which the or a compound of the formula (II) of component (B) is:
X ^b is selected from the group consisting of Cl, Br, OH, alkoxy having 1 to 22 C atoms, aryloxy having 6 to 10 C atoms, acyloxy having 1 to 22 C atoms and alkylcarbonyl having 2 C atoms; and or
R ^b is selected from the group consisting of alkyl of 1 to 20 carbon atoms, alkenyl of 2 to 20 carbon atoms, alkynyl of 2 to 4 carbon atoms; Aryl of 6 to 10 C atoms; Alkylaryl of 7 to 28 carbon atoms, alkylalkenyl of 3 to 22 carbon atoms and alkenylaryl of 8 to 28 carbon atoms;
where R ^b is that optionally an H is replaced by a substituent.

Preferably, the optional substituent on the radical R ^{b is} selected from the group consisting of halogen and alkoxy.

Examples of preferred compounds of the formula (II) are glycidyloxypropyltrimethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropenyltrimethoxysilane, 3-isocyanatopropyltrimethoxysilane, bis [2- (3,4-epoxycyclohexyl) ethyl] tetramethyldisiloxane, 1,3-bis (glycidoxypropyl) tetramethyldisiloxane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane.

Preference is given to coating materials or multicomponent systems in which Y ^{b contains} a glycidyl or glycidyloxy group in the compound or a compound of the formula (II) of component (B).

Preferably, for the or a compound of the formula (II) of the component (B) in the coating materials or multicomponent systems:
^Xb is methoxy or ethoxy, preferably methoxy; Y ^b is 3-glycidyloxypropyl; p is 3; and q is 1.

Component (B) is preferably used in an amount of 30-70 mol%, preferably 40-50 mol%, based on the total amount of the components (A), (B), (C) and (D).

(C) crosslinking agent for the crosslinkable function of the radical Y ^b

In order to ensure crosslinking of the crosslinkable function of the radical Y ^{b of} the compound of the formula (II), in the coating materials or multicomponent systems 2-25 mol%, preferably 2-20 mol%, based on the total amount of the components (A), ( B), (C) and (D) are used on one or more crosslinking agents.

The crosslinking agent in the coating materials or multicomponent systems is preferably Lewis bases. If the crosslinkable function of the radical Y ^{b of} the compound of the formula (II) is epoxide, amines are preferred as crosslinking agents; if the crosslinkable function is isocyanate, alcohols are preferred as crosslinking agents. Alcohols are particularly preferred for crosslinking isocyanates; an addition of, for example, 1,4-diazabicyclo [2.2.2] octane, N, N-dimethylaminoethanol, N, N-dimethylcyclohexylamine or N, N-dimethylcetylamine in catalytic amounts accelerates the reaction. Acryloxy or methacryloxy are alternatively z. B. crosslinked using radical initiators, z. By using 2,2-azobis (2-methylbutyronitrile) when thermally cured or by using a UV initiator (eg an α-hydroxyketone such as 1-hydroxycyclohexylphenyl ketone) on UV curing.

Preferably (and depending on the functional radicals Y ^{b of} the compound of formula (II)) are used as crosslinking agents in the coating materials or multicomponent systems: aromatic polyols, aromatic diols, nitrogen-containing heterocycles, phenols having one or more non-substituted amino groups, phenols having a or more substituted amino groups, polycyclic amines, ammonia, silanes having one or more unsubstituted amino groups, silanes having one or more substituted amino groups, and mixtures thereof. Particularly preferred are bisphenol A, bisphenol S, dihydroxynaphthalene, 1-methylimidazole, 2- (N, N-dimethylaminomethyl) phenol, aminopropyltrimethoxysilane and aminopropyltriethoxysilane.

Preferred crosslinking agents for Y ^b = isocyanate are polyether polyols, preferably linear polyether polyols such as Desmophen ^® 1100 Desmophen ^® 1200 Desmophen ^® 1800 (each manufacturer: Bayer)

In the case of aromatic polyols (eg bisphenol A, bisphenol S) typically 0.3 to 1.0 mol of hydroxy groups are used per mol of epoxy groups present in the coating material or multicomponent system, in the case of 1-methylimidazole or 2- (N, N-dimethylaminomethyl) phenol typically 0.05 to 0.5 moles of the respective compound per mole of epoxy groups.

(D) organo-metal compound

For the formation of covalent bridges between silicon atoms and metal atoms of a metallic substrate, 0-40 mol%, based on the total amount of the components (A), (B), (C) and (D), of one or more organozirconium, Organo-titanium or organo-aluminum compounds are used with hydrolyzable organic radicals in the coating materials or multi-component systems. In some cases, it is preferable to completely dispense with component (D) in the coating materials or multicomponent systems or to use only small amounts thereof, e.g. 0-30 mol%, 0-20 mol% or 0-15 mol%, based on the total amount of the components (A), (B), (C) and (D), at the expense of hardness to achieve a better elasticity of the cured layer. Our own investigations have shown that for a good adhesion of the coatings component (D) is not always necessary. Preferred for the coating materials or multicomponent systems compounds of component (D) are zirconium (IV) propoxide, titanium n-butoxide and aluminum sec-butoxide, preferably zirconium (IV) propoxide is used.

(E) hydrolysis catalyst

In the coating materials or multicomponent systems, the hydrolysis catalyst used is preferably an acidic catalyst or a mixture of different acidic catalysts. Preference is given to HCl, HNO ₃ , H ₂ SO ₄ , H ₃ PO ₄ and CH ₃ COOH and mixtures thereof. Typical amounts of water used for the hydrolysis are 0.5-1.5 mol per hydrolyzable group.

(F) prepolymer

Epoxy resins and / or epoxy siloxane resins are used as prepolymers in the coating materials or multicomponent systems. It has been found that the presence of suitable prepolymers is essential for achieving the object of the present invention. The prepolymers primarily serve to establish a high elasticity of the cured coating and may additionally affect the degree of covalent network formation, hardness and barrier function of the cured coating, and viscosity and pot life of the incompletely cured coating material.

In some cases, it is preferable not to use too high levels of component (F). In such cases, preference is given to coating materials or multicomponent systems in which component (F) is present in a proportion of at most 10% by weight, preferably at most 5% by weight, based on the total weight of components (A), (B), (C) and (D).

Decisive for the success of the invention is the presence of at least one prepolymer having an epoxy equivalent weight of at least 200. Preferred is the presence of a prepolymer having an epoxy equivalent weight of at least 230, more preferably at least 260, most preferably at least 300.

If an excessively high proportion of prepolymers having an epoxy equivalent weight of less than 200 is present, the resulting coating material or multicomponent system for producing a coating is not capable of simultaneously exhibiting high elasticity after application to an aircraft structural component having at least one rivet good barrier and effective adhesion to ensure different materials. Therefore, the proportion of optionally present prepolymers having an epoxy equivalent weight of less than 200 at a maximum of 5 wt .-%, based on the total weight of components (A), (B), (C) and (D). In any case, the proportion of prepolymers having an epoxy equivalent weight of less than 200 must not be greater than the proportion of prepolymers having an epoxy equivalent weight of at least 200.

Particularly suitable prepolymers are for example the substances sold under the following trade names: DER ^® 337, DER ^® 732 (each manufacturer: Dow epoxy resin), SILIKOPON ^® EF (manufacturer: TEGO), and Tegomer ^® ESi 2330 (manufacturer: TEGO).

When using a polyepoxide of component (F) and a compound of component (B) containing methacryloxy or isocyanate groups, interpenetrating networks are regularly formed, i. H. On the one hand there is a cross-linking of the methacryloxy or isocyanate groups and on the other hand a network formation of the polyepoxide. Addition of amines in catalytic amounts is often advantageous.

(G) corrosion inhibitor

Optionally, one or more corrosion inhibitors selected from the group consisting of inorganic and organic corrosion inhibitors are included in the coating materials or multi-component systems. These serve in particular for the passivation of "exposed" base material in the event of damage to the applied sol-gel coating and are either dispersed in the finished sol or already introduced during the hydrolysis (see below). The proportion of corrosion inhibitors is preferably in the range of 0-10 wt .-%, more preferably 3-6 wt .-%, based on the total weight of components (A), (B), (C) and (D).

Preferred inorganic corrosion inhibitors in the coating materials or multicomponent systems are those selected from the group consisting of vanadates, borates, phosphates, molybdate, tungstates, oxides and mixtures thereof and / or containing at least one element selected from the group consisting of cerium, Yttrium, lanthanum, titanium and zirconium. Preferably, an inorganic corrosion inhibitor comprises oxide nanoparticles selected from the group consisting of titanium oxide, zirconium oxide and cerium oxide, vanadium oxide, zinc oxide and mixtures thereof.

Preferred organic corrosion inhibitors in the coating materials or multicomponent systems are selected from the group consisting of triazoles (in particular benzotriazole, 5-methylbenzotriazole and 2-mercaptobenzothiazole and mixtures thereof), 2-benzothiazolythiosuccinic acid, zinc 5-nitroisophthalate and mixtures thereof.

(H) Compound for reducing the reactivity of component (D)

In the coating materials or multicomponent systems, compounds for reducing the activity of the organometal compound of component (D) (if present) are preferably included. It is preferably a chelator or a mixture of different chelators. Preference is given to acetylacetone, ethyl acetoacetate, propionic acid and mixtures thereof. Typically, chelators are used in a 1: 2 molar ratio to the hydrolyzable moieties of component (D).

The coating materials or multicomponent systems preferably have a combination of the configurations identified above as being preferred for the individual components (A) to (H).

In particular, coating materials or multicomponent systems are preferred
20 to 40 mol% of component (A),
40 to 50 mol% of component (B), and / or
2 to 20 mol% of component (C), and / or
0 to 30 mol% of component (D),
based on the total amount of the components (A), (B), (C) and (D).

Preference is given to coating materials or multicomponent systems
where for component (A):
X ^a is selected from the group consisting of F, Cl, Br, I, OH, alkoxy, aryloxy, acyloxy, alkylcarbonyl and alkoxycarbonyl;
R ^a is selected from the group consisting of alkyl, alkenyl, alkynyl, aryl, arylalkyl, alkylaryl, arylalkenyl, alkenylaryl, arylalkynyl, alkynylaryl and alkylalkenyl;
where for component (B):
X ^b is selected from the group consisting of F, Cl, Br, I, OH, alkoxy, aryloxy, acyloxy, alkylcarbonyl and alkoxycarbonyl;
R ^b is selected from the group consisting of alkyl, alkenyl, alkynyl, aryl, arylalkyl, alkylaryl, arylalkenyl, alkenylaryl, arylalkynyl, alkynylaryl and alkylalkenyl;
where for component (C):
the crosslinking agent (s) are Lewis bases;
wherein component (D) is selected from the group consisting of tetra-n-propoxyzirconium, tetra-i-propoxyzirconium, titanium n-butoxide and aluminum sec-butoxide;
wherein component (E) is an acid catalyst or a mixture of different acidic catalysts; and
where component (H) is a chelator or a mixture of different chelators.

Furthermore, the coating materials or multicomponent systems in this field may contain conventional additives, such as UV stabilizers, photoinitiators, photosensitizers, thermal polymerization catalysts, leveling agents or colorants.

• – Bereitstellen eines Substrats,
• – Bereitstellen oder Herstellen eines nicht vollständig gehärteten Beschichtungsmaterials wie vorstehend definiert (vorzugsweise in einer der vorstehend als bevorzugt bezeichneten Ausgestaltungen),
• – Härten oder Weiterhärtenlassen des Beschichtungsmaterials und
• – Zumindest bereichsweises Aufbringen des Beschichtungsmaterials auf das Substrat vor dem oder während des Härtens.

The coated substrates can be prepared by a process with the following steps:

• Providing a substrate,
• Providing or producing an incompletely cured coating material as defined above (preferably in one of the embodiments referred to above as preferred),
• Curing or further hardening of the coating material and
• At least partially applying the coating material to the substrate before or during curing.

Preferably, in one method, the substrate is chemically pre-cleaned, physically pre-cleaned, leached, primed, exposed to electrical discharge, exposed to an atmospheric pressure plasma process, CO ₂ -blasted, treated with an abrasive media, and / or baked out prior to application of the coating.

The application of the coating material takes place in a process by techniques familiar to the person skilled in the art, preferably by spraying or dipping.

The preferred embodiments for the coating materials or multicomponent systems are also preferred for the process.

The present invention relates to coated substrates obtainable by a process.

• – Mischen der Komponenten (A), (B) und (C),
• – Hydrolysieren der hydrolysierbaren Gruppen der Komponenten (A) und (B),
• – Zugeben der Komponente (F) vor, während und/oder nach der Hydrolyse,
• – Vernetzen vernetzbarer Gruppen der Komponenten (B) und/oder (F).

The coating materials can be prepared by a process comprising the following steps:

• Mixing the components (A), (B) and (C),
• Hydrolyzing the hydrolyzable groups of components (A) and (B),
• Adding the component (F) before, during and / or after the hydrolysis,
• - Crosslinking crosslinkable groups of components (B) and / or (F).

In some cases it is preferred to add component (F) after hydrolysis. In other cases, it is preferable to add component (F) during the hydrolysis.

It is preferred to initiate or accelerate crosslinking by appropriate means (e.g., induced cracking of an additional added radical initiator and / or incubating at a temperature of at least 20 ° C) after hydrolysis. When using a component (B) having a radical Y ^b , which is acryloxy or methacryloxy, is preferably a UV initiator (eg., An alpha-hydroxy ketone such as 1-hydroxy-cyclohexyl-phenyl-ketone) or ., a thermal free radical initiator such as 2,2-azobis (2-methylbutyronitrile) (Vazo 67 ^®) are used.

A coated substrate according to the invention is an aircraft structure. The substrate consists of at least one connecting element or comprises at least one connecting element. The connecting element is preferably a rivet. Preferred is a connecting element comprising or consisting of one or more materials selected from the group consisting of aluminum, titanium and steel and the products of a near-surface oxidation of these materials.

The coated substrate according to the invention comprises at least one connecting element in contact with at least one further substrate body, wherein the further substrate body is painted, wherein the coating covers a joint between the connecting element and the further substrate body and wherein the coating both on the connecting element and on the paint the further substrate body is applied. Preferably, no further protective layer is provided in the case of a coated substrate according to the invention.

In the case of a coated substrate according to the invention, several configurations identified as being preferred are preferably combined with one another. The preferred embodiments for the coating materials or multicomponent systems or the method are also preferred for the coated substrates according to the invention.

Preferred is a coated substrate according to the invention,
wherein the substrate is an aircraft structure
comprising a structural member having at least one rivet consisting of one or more materials selected from the group consisting of aluminum, titanium and steel and the products of near-surface oxidation of these materials,
obtainable by a process comprising providing or producing a non-fully cured (preferred) coating material,
wherein no further protective layer is provided.

Further preferred embodiments will become apparent from the following examples and claims. The following examples further illustrate the present invention.

Examples:

Example 1 Coating Material with Epoxy Functional Component (B) phenyltrimethoxysilane 3-glycidoxypropyltrimethoxysilane aminopropyltriethoxysilane Zirconium (IV) propoxide acetoacetate H ₂ O THE 732 component (A) (B) (C) (D) (H) (F) Block I 59.5 g 118.17 g 22.14 g - - - - Block II - - - 32.76 g 13.0 g - - Block III - - - - - 54 g - Block IV - - - - - - 10 g

To prepare Block I, components (A), (B) and (C) are mixed. Block I is stirred with ice-cooling. Block II is prepared by adding component (H) to component (D). Block II is slowly added dropwise to Block I. Then, to the resulting mixture, block III (H ₂ O) is added slowly with stirring and under ice-cooling, followed by stirring for 2 hours. After completion of the hydrolysis 10 g of block IV are stirred. Special paint properties such. B. wetting (wetting) the surface and a homogeneous layer formation on the substrate by coating additives (e.g. B .: leveling additives, such as polyether-modified polydimethylsiloxanes;.. Defoamers, such as TEGO ^® Foamex 800, a siliceous polyether siloxane copolymer. ) and solvents.

The coating material can be applied to substrates (eg aluminum alloys) in layer thicknesses of 3-15 μm. For networking z. B. incubated at room temperature for 24 h or at a temperature in the range of 60 ° C to 120 ° C for 1 h. Example 2 Coating Material with Isocyanate-Functional Component (B) phenyltrimethoxysilane isocyanatopropyltrimethoxysilane Bisphenol A Zirconium (IV) propoxide acetoacetate 0.1 M HNO ₃ THE 732 component (A) (B) (C) (D) (H) (E) (F) Block I 59.5 g 102.65 g 45.66 g - - - - Block II - - 32.76 g 13.0 g - - Block III - - - - 43.2 g 10 g

To prepare Block I, components (A), (B) and (C) are mixed. Block I is stirred with ice-cooling. Block II is prepared by adding component (H) to component (D). Block II is slowly added dropwise to Block I. Subsequently, block III, which is prepared by mixing component (E) with component (F), is slowly added with stirring and under ice-cooling, followed by stirring for 2 hours. Special coating properties are set analogously to Example 1 by coating additives and solvents.

As free-radical initiator, 4.62 g of Vazo67 can be added shortly before coating (manufacturer: DuPont).

The coating material can be applied in particular to layer thicknesses of 3-15 μm on substrates (see above). For crosslinking is incubated at a temperature in the range of 60 ° C to 120 ° C for 1 h.

The curing of the layers according to Examples 1 and 2 is preferably carried out by heat (temperature increase). In this case, an SiO ₂ network is formed, since water and alcohols evaporate and the previously existing hydrolysis-condensation equilibrium is shifted in the direction of condensation. Without temperature increase, the addition of organic tin salts is possible to effect the formation of the SiO ₂ network. However, due to the toxicity of these substances, this process variant is not preferred.

Example 3: Impact Test

On a substrate of the type AA2024 unclad (aluminum alloy), the coating material according to Example 1 is applied and cured by increasing the temperature (see above).

The resulting coating does not burst from the substrate.

Example 4: Adhesion Test (ISO 2409)

As in Example 3, coating materials according to Example 1 are applied to a substrate of the type AA2024 unclad. The applied layers are cured and subjected to an adhesion test according to ISO 2049. The liability proves to be excellent.

Example 5: Salt Spray Test (ASTM B117)

The coating material of Example 1 is applied to a substrate of the type AA2024 clad and subjected to a salt spray test according to ASTM 8117 (500 h SST). It is examined whether the applied layer is infiltrated from a scratch. An infiltration is not apparent in the present coating.

Claims (35)

A coated substrate, wherein the substrate is an aircraft structure and comprises at least one connecting element or at least one connecting element, wherein the substrate further comprises at least one connecting element in contact with at least one further substrate body, wherein the further substrate body is painted, wherein the coating is a gap between the coating element and the further substrate body is covered, wherein the coating is applied both on the connecting element and on the paint of the further substrate body, wherein the coated substrate is obtainable by a method for producing a coating on a substrate, comprising the following steps: providing a Substrate, - Provision or production of an incompletely cured coating material, - Hardening or hardening of the coating material and - At least partially applying the coating material to the Substrate before or during curing and wherein the coating material which can be prepared using the following components or multicomponent system for producing a coating comprises or consists of the following components: (A) 15-50 mol% of one or more organosilicon compounds of the formula (I) R ^a _4-n SiX ^a _n (I), where: each X ^a is independently of any other X ^a a hydrolyzable group; each R ^a is independently of any other R ^a is a non-hydrolysable radical; n is 2, 3 or 4; (B) 30-70 mol% of one or more organosilicon compounds of the formula (II)

wherein: each X ^b is a hydrolyzable group independently of any other X ^b ; R ^b is a non-hydrolyzable radical without epoxide function, without acryloxy function, without methacryloxy function and without isocyanate function; each Y ^b is independently of any other Y ^b a non-hydrolyzable radical having a crosslinkable function selected from the group consisting of epoxide, acryloxy, methacryloxy and isocyanate p is 2 or 3; q is 1 or 2; the sum of p and q is less than or equal to 4; (C) 2-25 mol% of one or more crosslinking agents for the crosslinkable function of the radical Y ^b ; (D) 0-40 mol% of one or more organo-zirconium, organo-titanium or organo-aluminum compounds having hydrolyzable organic radicals, to form covalent bridges between silicon atoms and metal atoms of a metallic substrate; (E) optionally one or more hydrolysis catalysts; (F) one or more crosslinkable prepolymers selected from the group consisting of epoxy resins and epoxy siloxane resins and mixtures thereof, the one or more or all of the prepolymers having an epoxy equivalent weight of at least 200, wherein the proportion optionally present prepolymers having an epoxy equivalent weight of less than 200 at a maximum of 5 wt .-%, based on the total weight of components (A), (B), (C) and (D), wherein the proportion of optionally present prepolymers having an epoxy equivalent weight of less than 200 is not greater than the proportion of prepolymers having an epoxy equivalent weight of at least 200; and optionally (G) one or more corrosion inhibitors selected from the group consisting of inorganic and organic corrosion inhibitors; and optionally (H) one or more compounds to reduce the reactivity of component (D); wherein the mole percentages are based on the total amount of the components (A), (B), (C) and (D), provided that n and the sum of p + q are not all 4 simultaneously. Coated substrate according to claim 1, wherein, for the coating material or multicomponent system: X ^a and / or X ^b is selected from the group consisting of F, Cl, Br, I, OH, alkoxy, aryloxy, acyloxy, alkylcarbonyl and alkoxycarbonyl; and or R ^a and / or R ^b is selected from the group consisting of alkyl, alkenyl, alkynyl, aryl, arylalkyl, alkylaryl, arylalkenyl, alkenylaryl, arylalkynyl, alkynylaryl and alkylalkenyl; wherein for R ^a and R ^{b in} each case applies that optionally an H is replaced by a substituent. Coated substrate according to one of the preceding claims, wherein for the coating material or multicomponent system: X ^a and / or X ^b is selected from the group consisting of Cl, Br, OH, alkoxy having 1 to 22 carbon atoms, aryloxy having 6 to 10 C atoms, acyloxy having 1 to 22 C atoms and alkylcarbonyl having 2 C atoms; and / or R ^a and / or R ^b is selected from the group consisting of alkyl having 1 to 20 C atoms, alkenyl having 2 to 20 C atoms, alkynyl having 2 to 4 C atoms; Aryl of 6 to 10 C atoms; Alkylaryl of 7 to 28 carbon atoms, alkylalkenyl of 3 to 22 carbon atoms and alkenylaryl of 8 to 28 carbon atoms; wherein for R ^a and R ^{b in} each case applies that optionally an H is replaced by a substituent. Coated substrate according to one of the preceding claims, wherein for the coating material or multicomponent system: n is 2 or 3, and R ^a is a non-crosslinkable radical. Coated substrate according to one of the preceding claims, wherein, for the coating material or multicomponent system, X ^a is methoxy or ethoxy, preferably methoxy; R ^a is selected from the group consisting of methyl, ethyl, propyl, hexadecyl, (cyclohexyl) methyl, (octadecyl) methyl, isooctyl, dicyclopentyl and phenyl; and n is 2 or 3. Coated substrate according to one of the preceding claims, wherein, for the coating material or multicomponent system: X ^a is methoxy; R ^a is phenyl; and n is 3. Coated substrate according to one of the preceding claims, wherein the following applies to the coating material or multicomponent system: Y ^b contains a glycidyl or glycidyloxy group. Coated substrate according to one of the preceding claims, wherein, for the coating material or multicomponent system, X ^b is methoxy or ethoxy, preferably methoxy; Y ^b is 3-glycidyloxypropyl; p is 3; and q is 1. A coated substrate according to any one of claims 2 to 8, wherein R ^a and / or R ^{b of} the coating material or multi-component system comprises a substituent selected from the group consisting of halogen and alkoxy. Coated substrate according to one of the preceding claims, wherein the following applies to the coating material or multicomponent system for component (C): the crosslinking agent (s) are Lewis bases. Coated substrate according to one of the preceding claims, wherein the following applies to the coating material or multicomponent system for component (C): the crosslinking agent (s) are selected from the group consisting of aromatic polyols, aromatic diols, nitrogen-containing heterocycles, phenols with one or more unsubstituted amino groups, phenols with one or more substituted amino groups, polycyclic amines, ammonia, silanes with one or more non-substituted substituted amino groups, silanes having one or more substituted amino groups and mixtures thereof. Coated substrate according to one of the preceding claims, wherein the following applies to the coating material or multicomponent system for component (C): the crosslinking agent (s) are selected from the group consisting of bisphenol A, bisphenol S, dihydroxynaphthalene, 1-methylimidazole, 2- (N, N-dimethylaminomethyl) phenol, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, polyether polyols. Coated substrate according to one of the preceding claims, wherein component (D) of the coating material or multicomponent system is selected from the group consisting of: Zirconium (IV) propoxide, titanium n-butoxide and aluminum sec-butoxide preferably zirconium (IV) propoxide is used. Coated substrate according to one of claims 1 to 12, wherein component (D) of the coating material or multicomponent system is omitted. A coated substrate according to any one of the preceding claims, wherein component (E) of the coating material or multicomponent system is an acidic catalyst or a mixture of different acidic catalysts. Coated substrate according to one of the preceding claims, wherein component (E) of the coating material or multicomponent system is selected from the group consisting of HCl, HNO ₃ , H ₂ SO ₄ , H ₃ PO ₄ and CH ₃ COOH and mixtures thereof. Coated substrate according to one of the preceding claims, wherein component (F) of the coating material or multicomponent system is present in a proportion of at most 10% by weight, preferably at most 5% by weight, based on the total weight of components (A), (B ), (C) and (D). Coated substrate according to one of the preceding claims, wherein component (G) of the coating material or multicomponent system is an inorganic corrosion inhibitor and is selected from the group consisting of vanadates, bristles, phosphates, Molybdate, tungstates, oxides and mixtures thereof; and or at least one element selected from the group consisting of cerium, yttrium, lanthanum, titanium and zirconium. A coated substrate according to any one of the preceding claims, wherein component (G) of the coating material or multicomponent system is an inorganic corrosion inhibitor and comprises oxidic nanoparticles selected from the group consisting of titanium oxide, zirconium oxide and ceria, vanadium oxide, zinc oxide and mixtures thereof. A coated substrate according to any one of the preceding claims, wherein component (G) of the coating material or multicomponent system comprises one or more organic corrosion inhibitors selected from the group consisting of triazoles, 2-benzothiazolythiosuccinic acid, zinc 5-nitroisophthalate and mixtures thereof. A coated substrate according to any one of the preceding claims, wherein component (G) of the coating material or multicomponent system comprises one or more organic corrosion inhibitors selected from the group consisting of benzotriazole, 5-methylbenzotriazole, 2-mercaptobenzotriazole and mixtures thereof. Coated substrate according to one of the preceding claims, wherein component (H) of the coating material or multicomponent system is a chelator or a mixture of different chelators. Coated substrate according to one of the preceding claims, wherein component (H) of the coating material or multicomponent system is selected from the group consisting of acetylacetone, ethyl acetoacetate, propionic acid and mixtures thereof. Coated substrate according to one of the preceding claims, wherein the coating material or multi-component system 20 to 40 mol% of component (A), 40 to 50 mol% of component (B), and / or 2 to 20 mol% of component (C), and / or 0 to 30 mol% of component (D) includes, based on the total amount of the components (A), (B), (C) and (D). A coated substrate according to claim 24, wherein, for the coating material or multi-component system for component (A): X ^a is selected from the group consisting of F, Cl, Br, I, OH, alkoxy, aryloxy, acyloxy, alkylcarbonyl and alkoxycarbonyl; R ^a is selected from the group consisting of alkyl, alkenyl, alkynyl, aryl, arylalkyl, alkylaryl, arylalkenyl, alkenylaryl, arylalkynyl, alkynylaryl and alkylalkenyl; for component (B), X ^b is selected from the group consisting of F, Cl, Br, I, OH, alkoxy, aryloxy, acyloxy, alkylcarbonyl and alkoxycarbonyl; R ^b is selected from the group consisting of alkyl, alkenyl, alkynyl, aryl, arylalkyl, alkylaryl, arylalkenyl, alkenylaryl, arylalkynyl, alkynylaryl and alkylalkenyl; for component (C): the crosslinking agent (s) are Lewis bases; is that component (D) is selected from the group consisting of tetra-n-propoxyzirconium, tetra-i-propoxyzirconium, titanium n-butoxide and aluminum sec-butoxide; it is true that component (E) is an acidic catalyst or a mixture of different acidic catalysts; and that component (H) is a chelator or a mixture of different chelators. The coated substrate of any one of the preceding claims, wherein in the method of forming a coating on a substrate, the substrate is chemically pre-cleaned, physically prepurified, leached, primed, exposed to an electrical discharge, exposed to an atmospheric pressure plasma process, CO ₂ prior to application of the coating -blasted, treated with an abrasive medium and / or baked out. Coated substrate according to one of the preceding claims, wherein in the method for producing a coating on a substrate, the application of the coating material by spraying or dipping. A coated substrate according to any one of claims 1 to 25, wherein the coating material is obtainable by a process for producing a coating material, comprising the steps of: Mixing the components (A), (B) and (C), Hydrolyzing the hydrolyzable groups of components (A) and (B), Adding the component (F) before, during and / or after the hydrolysis, - Crosslinking of the crosslinkable groups of components (B) and (F). A coated substrate according to claim 28, wherein in the process for producing a coating material, component (F) is added after the hydrolysis. A coated substrate according to claim 28, wherein in the process for producing a coating material, component (F) is added during the hydrolysis. The coated substrate according to claims 28 to 30, wherein in the process for producing a coating material, the crosslinking is initiated or accelerated after the hydrolysis. Coated substrate according to one of the preceding claims, wherein the connecting element is a rivet. Coated substrate according to one of the preceding claims, wherein: the connecting element comprises or consists of one or more materials selected from the group consisting of aluminum, titanium and steel and the products of near-surface oxidation of these materials. Coated substrate according to one of the preceding claims, wherein no further protective layer is provided. Coated substrate according to claim 34, wherein the substrate is an aircraft structure comprising a structural member having at least one rivet consisting of one or more materials selected from the group consisting of aluminum, titanium and steel and the products of near-surface oxidation of these materials, obtainable by a process for producing a coating on a substrate according to claim 1, which comprises providing or producing a non-fully cured coating material according to claim 1.