Parts of automobiles or motorcycles including titania-based coatings

Abstract

The present invention relates to a part for an automobile or motorcycle, comprising a metal substrate and a coating for said substrate. 2 and is obtained by a sol-gel process comprising a step of applying a colloidal solution onto a metal substrate of an automobile or motorcycle part. 2 It is obtained by hydrolysis and condensation reaction of inorganic precursor of TiO with water. 2 The inorganic precursor of the formula Ti(X) 4 and the X groups are equal to or different from each other and are hydrolyzable groups selected from the group consisting of halogen, -OR alkoxy groups and -COOR acyloxy groups, where R is preferably C 1 -C 6 It is an alkyl radical.

Description

[Technical field]

[0001] The present invention relates to a part for an automobile or motorcycle, in particular a brake caliper or brake disc, and relates to a metal substrate and a TiO 2 Furthermore, the present invention provides a coating comprising TiO 2 to impart self-cleaning properties to a metal substrate to which said coating is applied. [Background technology]

[0002] In the automotive sector, the problem of dust, mud, dirt, etc. adhering to the metal parts of a vehicle, particularly the metal parts of the vehicle's braking system, such as calipers and brake discs, is keenly felt.

[0003] The appearance of such parts can be affected by exposure to the environment. Indeed, the accumulation of mud during vehicle use and dust while the vehicle is stopped or parked can detract from the aesthetics of the parts themselves. Furthermore, contamination with organic compounds can damage the finish of such parts through phenomena such as sandblasting and decorative oxidation.

[0004] Dirt build-up is not just an aesthetic problem: adsorption of water, oxygen or aggressive ions can initiate corrosion processes and damage the components themselves.

[0005] The above problems are most evident in high-end and high-performance vehicles, such as luxury cars and racing bikes, where greater emphasis is placed on detail and performance.

[0006] The problem that the present invention aims to solve is therefore that of providing a coating for motor vehicle and motorcycle parts, in particular for parts of motor vehicle and motorcycle brake systems, which reduces the adhesion of dust, mud and other unwanted elements, protects said parts from soiling and is able to protect their surface from aggressive cleaning procedures. Summary of the Invention

[0007] The above problems are solved by the use of an automobile or motorcycle part, a method for manufacturing said part, and a sol-gel coating, which imparts self-cleaning properties to the metal substrate to which it is applied, as outlined in the appended claims, the definitions of which form an integral part of this specification.

[0008] A first object of the present invention is to provide a method for producing a metal substrate comprising the steps of: 2 the coating being obtained by a sol-gel process, the sol-gel process comprising the step of applying a colloidal solution onto the metal substrate of the part of the motor vehicle or motorcycle, The colloidal solution is TiO 2 and water, TiO 2 The inorganic precursor of formula Ti(X) 4 wherein the X groups are equal to or different from each other and are hydrolyzable groups selected from the group consisting of halogen, -OR alkoxy groups and -COOR acyloxy groups, and wherein R is preferably C 1 -C 6 It is an alkyl radical.

[0009] A second object of the invention is a method for manufacturing said component of a motor vehicle or motorcycle, comprising the steps of: Providing a motor vehicle or motorcycle component made of a metal substrate; On the metal substrate, TiO 2applying a colloidal solution obtained from the hydrolysis and condensation reaction of the inorganic precursor of the formula (I) with water, The inorganic TiO 2 The precursor has the formula Ti(X) 4 and the X groups are equal to or different from each other and are hydrolyzable groups selected from the group consisting of halogen, -OR alkoxy groups and -COOR acyloxy groups, where R is preferably C 1 -C 6 is an alkyl radical.

[0010] Another object of the present invention is to use the coating obtainable by said process to impart self-cleaning properties to the metal substrate to which the coating is applied, for example a metal substrate of an automobile or motorcycle part, in particular preferably made of aluminium or an aluminium alloy; or iron or an iron alloy, such as steel or cast iron; or titanium or a titanium alloy.

[0011] A further object of the invention is to use a colloidal solution as a coating for metal substrates, in particular for parts of automobiles or motorcycles, to impart self-cleaning properties to said coating, said colloidal solution being composed of TiO 2 The inorganic precursor Ti is obtained by hydrolysis and condensation reaction with water. 2 O 4 is the formula Ti(X) 4 and the X groups are equal to or different from each other and are hydrolyzable groups selected from the group consisting of halogen, -OR alkoxy groups, and -COOR acyloxy groups, where R is preferably C 1 -C 6 It is an alkyl radical.

[0012] The arrangement according to the invention advantageously exhibits self-cleaning properties.

[0013] Further features and advantages of the invention will become apparent from the following non-limiting description of some embodiments. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 shows a photograph of an AlSi7 alloy substrate provided with a coating made of TiO2 according to the invention before (A) and after (B) it has been subjected to an adhesion test according to standard ASTM D3359.

[0015] [Diagram 2] FIG. 2 is a graph comparing the UV-Visible light degradation rate of methylene blue dye on an AlSi7 alloy substrate coated with TiO2 in accordance with the present invention with the UV-Visible light degradation rate of methylene blue dye on an uncoated AlSi7 alloy substrate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention relates to a metal substrate and a TiO 2 and a coating for said substrate having a TiO 2 More specifically, the process comprises depositing, on the metal substrate, a TiO 2 The method includes the step of applying a colloidal solution resulting from the hydrolysis and condensation reaction of inorganic precursors of the formula (I) with water.

[0017] It has been observed that the components of the present invention have self-cleaning properties, exhibit photocatalytic activity against organic soils, and are highly water-repellent against sand and mud, which tend not to adhere to the metal substrates on which the components are coated.

[0018] Furthermore, the coating surprisingly showed high adhesion to the metal substrate to which it was applied, and also showed high transparency without causing any significant change in the color of the substrate to which it was applied, an effect that cannot be ignored in the automotive field.

[0019] The sol-gel process involves the synthesis of a colloidal solution, called a sol, which, through hydrolysis and condensation reactions, forms a precursor for the subsequent formation of an inorganic lattice, called a gel.

[0020] The term "colloidal solution" as used herein refers to the aforementioned TiO 2 1 shows the product obtained from the hydrolysis and condensation reaction that occurs between the inorganic precursor of and water.

[0021] The TiO 2 The inorganic precursor of the formula Ti(X) 4 and the X groups, which may be the same or different, are hydrolyzable groups selected from the group consisting of -OR alkoxy groups, -COOR acyloxy groups, and halogens. 1 -C 6 The alkyl groups are preferably Cl, Br, and I.

[0022] Preferably, the X group is an -OR alkoxy group, where R is selected from the group consisting of methyl, ethyl, propyl, and butyl. More preferably, the X group is an -OR alkoxy group, where R is selected from the group consisting of isopropyl and n-butyl.

[0023] Preferably, TiO 2 The inorganic precursor of is titanium tetraalkoxide (also called tetraalkyl titanate) in which the four alkoxy groups are equal to each other. Preferably, TiO 2 The inorganic precursors are titanium n-butoxide (TNBT) or titanium isopropoxide (TTIP).

[0024] According to different embodiments, the TiO 2 A colloidal solution can be obtained by reacting the inorganic precursor with water. Hereinafter, the colloidal solution obtained using the catalyst is referred to as "colloidal solution No. 1", and the colloidal solution obtained using the chelating agent is referred to as "colloidal solution No. 2".

[0025] Colloid Solution No.1 According to a first embodiment of the present invention, the colloidal solution comprises: - said at least one TiO 2 Inorganic precursors of; - At least one C 1 -C 4 alcohol; - water; by mixing catalysts for said hydrolysis and condensation reactions.

[0026] The inorganic precursor TiO 2 and water, C 1 -C 4 The components are mixed such that they react in the presence of an alcohol (forming a reaction solvent) and a catalyst to give the colloidal solution.

[0027] Preferably, said C 1 -C 4 The alcohol is selected from methanol, ethanol, isopropanol, isobutanol, n-butanol and mixtures thereof. Preferably, the alcohol is ethanol.

[0028] Preferably, C 1 -C 4 The alcohol is present in an amount of 40-90%, more preferably 50-80%, based on the total weight of the ingredients subjected to the sol-gel process.

[0029] Preferably, water is present in an amount of 1-20% by weight, more preferably 1-10% by weight, based on the total weight of the ingredients subjected to the sol-gel process.

[0030] Preferably, the catalyst is HNO 3 , HCl, H 2 SO 4 or an organic acid catalyst, such as, for example, acetic acid. More preferably, the catalyst is an inorganic acid catalyst, even more preferably HNO 3Preferably, the acid catalyst is added in an amount such that the pH is 2-3.5, or 2-3, preferably about 2.

[0031] Preferably, the TiO 2 The inorganic precursor of 1 -C 4 The molar ratio of alcohol, water and said catalyst is 1:20-60:1-5:0.01-0.1, more preferably 1:40-60:2-3:0.02-0.05.

[0032] According to a preferred embodiment, the colloidal solution is a mixture of titanium normal butoxide (TNBT), ethanol, water, and HNO. 3 Preferably, TNBT / ethanol / water / HNO 3 The molar ratio of is 1:50:2:0.04.

[0033] Preferably, the colloidal solution is heated to a temperature of at least 10° C. and up to 50° C., preferably at room temperature, to obtain a solution of the components (i.e., TiO 2 Inorganic precursor of C 1 -C 4 The term "room temperature" refers to a temperature above 18°C ​​and below 25°C.

[0034] Preferably, the step of mixing the ingredients is carried out for at least 15 hours, at least 16 hours, at least 17 hours, or at least 18 hours.

[0035] Preferably, the step of mixing the ingredients is carried out for a period of 18 to 24 hours, more preferably for a period of 20 to 24 hours, and even more preferably for a period of about 20 hours.

[0036] According to a preferred embodiment, the sol-gel process for obtaining said coating further comprises, after said step of applying said colloidal solution, a heat treatment step.

[0037] Preferably, said heat treatment step is carried out at a temperature of at least 350°C, preferably 350-500°C, more preferably about 400°C.

[0038] Preferably, the heat treatment step is carried out for a period of about 30-180 minutes, preferably about 1 hour.

[0039] Without being bound by theory, the drying and solidifying heat treatment step may remove the liquid phase from the gel and further promote the condensed phase.

[0040] Colloidal Solution No. 2 According to a second embodiment of the invention, the colloidal solution is obtained by mixing: - said at least one TiO 2 Inorganic precursors of; - At least one C 1 -C 4 alcohol; - water; A chelating agent, preferably acetylacetone.

[0041] The above component is C 1 -C 4 In the presence of an alcohol (forming the reaction solvent) and a chelating agent, the TiO 2 The inorganic precursors and water are mixed so as to react to obtain said colloidal solution.

[0042] Preferably, said C 1 -C 4 The alcohol is selected from methanol, ethanol, isopropanol, isobutanol, n-butanol and mixtures thereof. Preferably, the alcohol is ethanol.

[0043] Preferably, said at least one TiO 2 The inorganic precursor is present in an amount of 4-35% based on the total weight of the components subjected to the sol-gel process.

[0044] Preferably, C1 -C 4 The alcohol is present in an amount of 30-70% by weight based on the total weight of the ingredients subjected to the sol-gel process.

[0045] Preferably, water is present in an amount of 1-55% by weight based on the total weight of the ingredients subjected to the sol-gel process.

[0046] Preferably, the chelating agent is present in an amount of 1-10% by weight based on the total weight of the ingredients subjected to the sol-gel process.

[0047] According to an embodiment of the present invention, the colloidal solution is obtained by mixing titanium isopropoxide (TTIP) in an amount of 5-10% by weight, preferably about 6%; ethanol in an amount of 40-50% by weight, preferably about 41%; water in an amount of 50-60% by weight, preferably about 51%; and acetylacetone in an amount of between 2-5% by weight, preferably about 2%.

[0048] According to another embodiment of the present invention, the colloidal solution is obtained by mixing 25-30% by weight, preferably about 30% titanium isopropoxide (TTIP); 60-70% by weight, preferably about 65% ethanol; 1-5% by weight, preferably about 1.5% water; and 7-10% by weight, preferably about 9% acetylacetone.

[0049] Preferably, the process for obtaining the colloidal solution comprises the steps of: 2 The inorganic precursor of C 1 -C 4 The method includes a first step of mixing with alcohol, adding a chelating agent and stirring the resulting solution for about 10 to 60 minutes, preferably about 30 minutes, and adding water, preferably dropwise, and stirring the resulting solution for about 30 to 90 minutes, preferably about 1 hour, at room temperature, where the term "room temperature" means a temperature between 18°C ​​and 25°C.

[0050] According to one embodiment, the step of applying colloidal solution No. 2 to obtain said coating does not include a heat treatment step after the step of applying the colloidal solution, in contrast to the step of applying colloidal solution No. 1 to obtain said coating.

[0051] The following explanation uses colloidal solution No. 1 to measure TiO 2 The process for obtaining a coating consisting of TiO 2 and a process for obtaining a coating consisting of

[0052] The step of applying said colloidal solution onto the metallic substrate of the component according to the invention can be carried out using various techniques chosen from among spray coating, dip coating, spin coating and electrodeposition.

[0053] According to a preferred embodiment, said step of applying the colloidal solution onto the metal substrate of the component according to the invention is carried out by dip coating, according to which the metal substrate is immersed in the colloidal solution and withdrawn at a constant speed to allow evaporation of the solvent and gelation.

[0054] The withdrawal speed of the metal substrate from the colloidal solution determines the thickness of the resulting coating. Preferably, the withdrawal speed of the metal substrate from the colloidal solution is at least 100 mm / min, at least 150 mm / min, at least 200 mm / min, or at least 250 mm / min. More preferably, the withdrawal speed of the metal substrate from the colloidal solution is greater than 250 mm / min, even more preferably 300 mm / min-1000 mm / min, for example about 500 mm / min.

[0055] Preferably, the coating has a thickness of at least 50 nanometers. More preferably, the coating is TiO 2 The coating has a thickness between 1 and 5 micrometers, more preferably greater than 1 micrometer.

[0056] According to one embodiment, the metal substrate is aluminum or an aluminum alloy, such as an AlSi alloy, where x is 5, 7, 9, 10, 11.

[0057] According to another embodiment, the metal substrate is iron or an iron alloy, such as steel or cast iron.

[0058] According to a further embodiment, the metal substrate is titanium or a titanium alloy.

[0059] Optionally, the metal substrate is subjected to a particular treatment, for example anodizing.

[0060] In a preferred embodiment of the invention, said component is a brake caliper of a braking system of a motor vehicle or motorcycle, or a part of said brake caliper.

[0061] In another embodiment, the part is a disc of a braking system of a car or motorcycle, or a part of said disc, for example the part is the bell of said disc.

[0062] Experimental Example The colloidal solution was prepared as follows: titanium n-butoxide (TNBT) was dissolved in ethanol, then nitric acid and water were added dropwise to the solution containing TNBT and ethanol and kept under continuous stirring. The resulting solution was stirred at room temperature for 20 hours. The molar ratio of TNBT, ethanol, water, and nitric acid used was 1:50:2:0.04.

[0063] The solution was applied to an AlSi7 alloy substrate, for example for a brake caliper, by dip coating with a withdrawal speed of 500 mm / min.

[0064] The brake caliper made of the substrate thus coated was then subjected to a heat treatment at 400 °C for 1 hour to obtain TiO with an anatase crystalline phase. 2 A coating consisting of

[0065] The brake caliper obtained in the above process was subjected to the following tests.

[0066] 1) Adhesion test Cross-cut and tape tests were performed according to ASTM D3359 to evaluate the adhesion of the coating to the substrate. As is evident from the optical micrograph shown in Figure 1, the coating remained intact and passed the adhesion test.

[0067] 2) Transparency The transparency of the coating deposited on the substrate was verified by CIELAB or l*a*b chromaticity analysis to verify the color difference between the coated substrate according to the invention and the corresponding uncoated substrate. In the aforementioned test, a value of ΔE=3 was obtained, which indicates that the color is not significantly changed compared to the uncoated substrate. The obtained transparency level is considered suitable for applications in the automotive field.

[0068] 3) Contact angle Static contact angle measurements were performed to characterize the wetting behavior of coatings deposited on AlSi7 alloy substrates according to the UNI-828-2013 standard.

[0069] The contact angle was measured to be less than 10°, i.e. 83° less compared to the corresponding uncoated substrate, indicating the superhydrophilic behavior of the coated substrate according to the invention and therefore its excellent antifouling properties.

[0070] 4) Photocatalytic activity The photocatalytic activity was evaluated by monitoring the decomposition of an organic dye (methylene blue) on the substrates coated according to the invention and on the corresponding uncoated substrates under UV irradiation. In particular, the photocatalytic performance was evaluated by monitoring the change in the concentration of said organic dye over time using a UV-Visible spectrophotometer.

[0071] In the absence of illumination and photocatalysis, it was observed that the dye did not decompose, indicating that no adsorption phenomenon occurred on the surface of the substrate.

[0072] The UV stability of an organic dye (methylene blue) was also studied to be able to exclude the influence of the photodecomposition phenomenon of the dye on the photocatalytic activity results. Specifically, a 16.5 μM methylene blue solution was exposed to a UV fluorescent lamp (6 W, 800 uW / cm) with a maximum emission wavelength of 365 nm, 1 cm away from the sample. 2 The irradiation lasted for two hours, with aliquots taken and measured every 15 minutes. The results showed that even after two hours of irradiation, the dye concentration had decreased by only 2%.

[0073] TiO formed on an AlSi7 alloy substrate 2 To study the photocatalytic activity of the base coating, an initial solution of 16.5 μM methylene blue was prepared in which the coated samples were immersed. The reaction medium was illuminated by two UV fluorescent lamps (6 W, 800 uW / cm) with a maximum emission wavelength of 365 nm, placed 1 cm away from the samples. 2 ) on the substrate. The photocatalytic process was monitored by following the decrease in the absorbance intensity at 662 nm of the dye versus the irradiation time. The irradiation time lasted for 2 hours and was measured every 15 minutes with a UV-Vis spectrophotometer. The results obtained are shown in the graph of FIG. 2, which compares the time evolution of the degradation of methylene blue dye on a coated substrate with that of the same dye on an uncoated substrate. The process of the time evolution of the degradation is expressed as a degradation percentage or rate over time. On the uncoated substrate, no degradation of the aforementioned dye occurs, whereas on the coated substrate according to the invention, the degradation percentage is 18%, with TiO 2 The photocatalytic activity of the base coating is demonstrated.

[0074] 5) Sand adhesion test TiO 2A protocol has been developed to quantify the self-cleaning properties of the base coating, and in particular to quantify sand adhesion between a coated substrate according to the present invention and a corresponding uncoated reference substrate.

[0075] Sand particles were dropped onto the substrate from a funnel, the distance between the funnel and the substrate was 15 cm, and the amount of sand dropped onto the substrate was 25 grams.

[0076] The grain size distribution of the sand used in this test is less than 250 micrometers.

[0077] To carry out the test, two inclined planes were used, in this case a plane with an inclination angle of 20° and a plane with an inclination angle of 40°.

[0078] The amount of sand remaining on the substrate was determined by the weight difference of the substrate before and after the test. In particular, the fouling rate of the uncoated substrate was set to 100% and the fouling rate of the coated substrate was determined from that percentage.

[0079] The results obtained using a 20° inclined plane are shown in Table 1 below, and the results obtained using a 40° inclined plane are shown in Table 2 below.

[0080] [Table 1]

[0081] [Table 2]

[0082] As can be seen from the results reported in the table above, sand adhesion is higher for the uncoated reference substrate (100% fouling by weight), whereas the coated substrates according to the invention are less fouled.

[0083] The above results further show that sand adhesion decreases with increasing slope of the plane (gravity adhesion rate is 53.0303030% for a 20° slope plane and 12.3265306% for a 40° slope plane).

[0084] 6) Mud adhesion test The mud adhesion test was carried out following the same protocol as the sand adhesion test, i.e., mud (i.e., a drop of water mixed with sand) was dropped onto the coated substrate according to the invention and the corresponding uncoated substrate.

[0085] The same behavior was observed, ie low adhesion of mud droplets on the coated substrate according to the invention.

[0086] It is apparent that the above are only specific embodiments of the present invention, and those skilled in the art will be able to make all necessary modifications to the structure and method of the present invention to adapt it to their particular conditions, without departing from the scope of protection defined in the appended claims.

Claims

1. A component for an automobile or a motorcycle, comprising a metal substrate and a coating for the metal substrate, The coating contains TiO ２ and can be manufactured by the sol-gel method. wherein the sol-gel method includes a step of applying a colloidal solution to the metal substrate of the component for an automobile or a motorcycle, The colloidal solution is obtained from a hydrolysis and condensation reaction of an inorganic precursor of TiO ２ and water, The above-mentioned TiO ２ inorganic precursor has the formula Ti(X) ４ and where X groups are the same as or different from each other and are hydrolyzable groups selected from the group consisting of halogen, -OR alkoxy groups, and -COOR acyloxy groups, Here, R is preferably C １ -C ６ An alkyl radical, a part of an automobile or a motorcycle.

2. Said TiO ２ The part for an automobile or a motorcycle according to claim 1, wherein the inorganic precursor of is titanium n-butoxide (TNBT) or titanium isopropoxide (TTIP).

3. The component for an automobile or a motorcycle according to claim 1 or 2, wherein the colloidal solution is obtained by mixing the following: - The at least one TiO ２ inorganic precursor; - at least one C １ - C ４ alcohol, preferably ethanol; - Water; - A catalyst for hydrolysis and condensation reactions, preferably an inorganic acid catalyst selected from the group consisting of HNO ３ , HCl and H ２ SO ４ .

4. The inorganic precursor of TiO ２ , the molar ratio between the C １ -C ４ alcohol, water, and the inorganic acid catalyst is 1:20 - 60:1 - 5:0.01 - 0.1, the part of an automobile or a motorcycle according to claim 3.

5. The colloidal solution is obtained by mixing TNBT, ethanol, water, and HNO ３ and preferably has a molar ratio of TNBT / ethanol / water / HNO ３ of 1:50:2:0.04, for the part of an automobile or a motorcycle according to claim 3 or 4.

6. The component for an automobile or a motorcycle according to any one of claims 3 to 5, wherein the coating is obtained by a process further including a heat treatment step following the step of applying the colloidal solution.

7. The component for an automobile or a motorcycle according to claim 6, wherein the heat treatment step is carried out at a temperature of at least 350°C, preferably between 350 - 500°C, more preferably at about 400°C, preferably for about 30 minutes - about 180 minutes, for example, for about 1 hour.

8. The component for an automobile or a motorcycle according to claim 1 or 2, wherein the colloidal solution is obtained by the following mixing: - At least one TiO ２ inorganic precursor; - at least one C １ - C ４ alcohol, preferably ethanol; - Water; - A chelating agent, preferably acetylacetone.

9. The component for an automobile or a motorcycle according to claim 8, wherein the colloidal solution is obtained by the following mixing: Said at least one TiO in an amount of 4 - 35% by weight ２ of the inorganic precursor Said at least one C in an amount of 30 - 70% by weight １ -C ４ alcohol Water in an amount of 1 to 55% by weight ratio; Chelating agent in an amount of 1 to 10% by weight ratio; These ratios are based on the total weight of the components subjected to the sol-gel method.

10. The component for an automobile or a motorcycle according to claim 8 or 9, wherein the colloidal solution is obtained by mixing 5 - 10% TTIP, 40 - 50% ethanol, 50 - 60% water, and 2 - 5% acetylacetone by weight ratio.

11. The component for an automobile or a motorcycle according to claim 8 or 9, wherein the colloidal solution is obtained by mixing 25 - 30% TTIP, 60 - 70% ethanol, 1 - 5% water, and 7 - 10% acetylacetone by weight ratio.

12. The component for an automobile or a motorcycle according to any one of claims 1 - 11, wherein the step of applying the colloidal solution onto the metal substrate is carried out by dip coating in which the metal substrate is immersed in the colloidal solution.

13. The pulling-out speed of the metal substrate from the colloidal solution is higher than 250 mm / min, preferably from 300 mm / min to 1000 mm / min, more preferably about 500 mm / min, for the part of an automobile or a motorcycle according to claim 12.

14. The coating has a thickness of from 1 micrometer to 5 micrometers, preferably greater than 1 micrometer, for the part of an automobile or a motorcycle according to any one of claims 1 - 13.

15. The substrate is made of aluminum or an aluminum alloy; or iron or an iron alloy, such as steel or cast iron; or titanium or a titanium alloy, for the part of an automobile or a motorcycle according to any one of claims 1 - 14.

16. The part of the automobile or the motorcycle is a brake caliper of a braking device of an automobile or a motorcycle, or a part thereof, or The part of the automobile or the motorcycle is a brake disc of a braking device of an automobile or a motorcycle, or a part thereof, such as a bell of the brake disc, for the part of an automobile or a motorcycle according to any one of claims 1 - 15.

17. A method for manufacturing a component of an automobile or a motorcycle, comprising providing a component of an automobile or a motorcycle made of a metal substrate, Apply a colloidal solution obtained by hydrolysis and condensation reaction of an inorganic precursor of TiO ２ and water onto the metal substrate, The inorganic precursor of TiO ２ has the formula Ti(X) ４ and wherein the X groups are the same as or different from each other and are hydrolyzable groups selected from the group consisting of halogen, -OR alkoxy groups, and -COOR acyloxy groups, R is preferably C １ -C ６ an alkyl group, preferably, the metal substrate is made of aluminum or an aluminum alloy; or iron or an iron alloy, such as steel or cast iron; or titanium or a titanium alloy, for the method for manufacturing a component of an automobile or a motorcycle.

18. The colloidal solution is applied onto the metal substrate by dip coating in which the metal substrate is immersed in the colloidal solution, preferably, the pulling-out speed of the metal substrate from the colloidal solution is higher than 250 mm / min, preferably from 300 mm / min to 1000 mm / min, more preferably about 500 mm / min, for the method for manufacturing a component of an automobile or a motorcycle according to claim 17.

19. Use of a coating, The coating is obtained by the method of claim 17 or 18 in order to impart self-cleaning properties to a metallic substrate on which the coating is applied, in particular a metallic substrate of a motor vehicle or motorcycle part. Preferably, the substrate is made of aluminum or an aluminum alloy; or iron or an iron alloy, such as steel or cast iron; or titanium or a titanium alloy.

20. Use according to claim 19, wherein the thickness of the coating is from 1 micrometer to 5 micrometers, preferably at least 1 micrometer.

21. Use of a colloidal solution as a coating for a metallic substrate, in particular a metallic substrate of a motor vehicle or motorcycle part, the coating being imparted with self-cleaning properties. The colloidal solution is obtained by hydrolysis and condensation reactions of an inorganic precursor of TiO ２ and water, The inorganic precursor of TiO ２ has the formula Ti(X) ４ , where the X groups are the same as or different from each other and are hydrolyzable groups selected from the group consisting of halogen, -OR alkoxy groups, and -COOR acyloxy groups, and R is preferably C １ -C ６ alkyl radical Preferably, the inorganic precursor of TiO ２ is titanium n-butoxide (TNBT) or titanium isopropoxide (TTIP) for use.

22. The colloidal solution is - The at least one TiO ２ inorganic precursor; - At least one C １ - C ４ Alcohol, preferably ethanol; - water; - A catalyst for hydrolysis and condensation reactions, preferably HNO ３ , HCl and H ２ SO ４ The use according to claim 21, obtained by mixing an inorganic acid catalyst selected from the group consisting of.

23. The inorganic precursor of TiO ２ , the molar ratio between the C １ -C ４ alcohol, water, and the inorganic acid catalyst is 1:20 - 60:1 - 5:0.01 - 0.1, the use according to claim 22.

24. The colloidal solution is preferably TNBT / ethanol / water / HNO ３ in a molar ratio of 1:50:2:0.04, and is obtained by mixing TNBT, ethanol, water and HNO ３ The use according to claim 22 or 23, obtained by mixing.

25. Use according to claim 21, wherein the colloidal solution is obtained by mixing - said at least one TiO ２ inorganic precursor; - At least one C １ - C ４ Alcohol, preferably ethanol; - water; - a chelating agent, preferably acetylacetone.

26. Use according to claim 25, wherein the colloidal solution is obtained by mixing Said at least one TiO in an amount of 4 - 35% by weight ２ of the inorganic precursor at least one C in an amount of 30 to 70 percent by weight １ -C ４ alcohol; an amount of water in a weight ratio of from 1 to 55 percent; an amount of chelating agent in a weight ratio of from 1 to 10 percent, these percentages being relative to the total weight of the components subjected to the sol-gel process.

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