New process

Abstract

The present invention relates to a process for depositing at least one coating on at least one surface of a metal substrate. In particular, said process is suitable for giving greater hardness and flowability to the metal substrate and for giving better resistance to wear and corrosion to the metal substrate. Furthermore, the invention refers to a coated metal substrate.

Description

[0001] DESCRIPTION NEW PROCESS FIELD OF THE INVENTION

[0002] The present invention relates to a process for the deposition of at least one coating on at least one surface of a metal substrate.

[0003] BACKGROUND

[0004] Hard chromium plating, also called thick chromium plating or functional- technical chromium plating, is a galvanic process aimed at electrochemically depositing a chromium surface coating on the part of interest.

[0005] The electrodeposition process, which takes place through the partial or total introduction of the article to be coated into special systems containing, in most cases, a chromosulfuric electrolyte, allows obtaining surface coatings of considerable hardness, resistant to wear and corrosion, with thicknesses ranging from a few tens of microns to 1000 microns.

[0006] Generally, thick hard chromium plating is applied directly on substrates consisting of ferrous alloys such as weakly alloyed steels, alloyed steels (also stainless and hardened) and cast irons. In some cases the substrate may also consist of copper, nickel, or brass.

[0007] Thanks to its particular characteristics, chromium is a malleable material, resistant to high temperatures and, above all, stainless. In addition, its finish gives an added value to the aesthetic appearance of the surface on which it is applied. Its hardness also guarantees high scratch resistance.

[0008] Despite the advantageous characteristics that are given to the parts subjected to chromium plating, the use of chromium-based electrolytes has a very high environmental impact. In particular, hexavalent chromium, widely used in chromium plating processes, is one of the most dangerous environmental pollutants. In addition, hexavalent chromium is teratogenic and carcinogenic to humans. Its use requires very specific and costly safety procedures and produces polluting industrial waste. Finally, hexavalent chromium is very soluble in water and its dispersion in the environment can cause soil and groundwater pollution.

[0009] The currently known chromium plating processes, in addition, require a time of at least 5-6 hours to obtain a finished product with very high energy costs. The introduction of trivalent chromium only partially solved the above- mentioned problems. In fact, the production costs are even higher compared to the processes in which hexavalent chromium is used. In addition, also trivalent chromium is toxic at high concentrations.

[0010] Therefore, the need for a process that allows to achieve the benefits of the electrolytic chromium plating and that reduces production costs, environmental impact and toxicity to humans and animals is very much felt.

[0011] SUMMARY OF THE INVENTION

[0012] A first aspect of the present invention concerns a process for the deposition of at least one coating on at least one surface of a metal substrate comprising the steps of:

[0013] - applying on the at least one surface of the metal substrate a composition comprising a siloxane, and

[0014] - applying on the at least one surface of the metal substrate a composition comprising a mixture of petroleum-derived hydrocarbons, where the process does not involve the use of hexavalent chromium.

[0015] Preferably, the siloxane is a polysiloxane, more preferably the polysiloxane is dimethyl polysiloxane.

[0016] The first composition preferably comprises at least one siloxane in a concentration between 80 and 99% w / w (w / w) of the first composition, more preferably between 85 and 95% w / w.

[0017] Preferably, the mixture of hydrocarbons comprises hydrocarbons having carbon numbers in the range of C9 - C16 and having a boiling point between 130°C and 310°C, preferably between 150 and 290°C.

[0018] A second aspect of the present invention concerns a metal substrate with at least one surface comprising a first layer comprising at least one siloxane and a second layer comprising hydrocarbons having carbon numbers predominantly in the range of C9 - C16.

[0019] Preferably, at least one surface of the metal substrate has a hardness between 55 and 80 HRC, preferably between 60 and 75 HRC, wherein the hardness is assessed by the Rockwell (HR) test according to ISO 6508.

[0020] Further, at least one surface of the metal substrate preferably has an average roughness Ra < 0.5, pm, preferably an average roughness Ra < 0.4 pm wherein the roughness is assessed by a roughness meter.

[0021] The first layer preferably has a thickness between 5 and 20 micrometers (pm), more preferably between 8 and 15 pm and the second layer has a thickness between 5 and 25 micrometers (pm), more preferably between 8 and 20 pm.

[0022] The metal substrate is preferably obtained with the process described above.

[0023] DETAILED DESCRIPTION OF THE INVENTION

[0024] A first aspect of the present invention refers to a process for the deposition of at least one coating on at least one surface of a metal substrate. In particular, said process is suitable for giving greater hardness and flowability to the metal substrate and for giving better resistance to wear and corrosion to the metal substrate.

[0025] In a preferred embodiment of the invention, the process does not provide for the application or use of hexavalent or trivalent chromium in any of its steps.

[0026] In one embodiment, said metal substrate is a substrate comprising or consisting of a ferrous material or alloy. Preferably, the metal substrate is a ferrous substrate, more preferably it is a substrate comprising or consisting of a material selected from: iron, steel, preferably stainless steel, aluminum, copper and brass, and combinations thereof.

[0027] In one embodiment, said metal substrate is not limited by any shape, size or use. Thus, the process of the present invention is suitable for depositing at least one coating on any metal substrate.

[0028] In one embodiment, the process comprises at least one step, preferably at least two steps of depositing at least one coating or layer on at least one surface of the metal substrate.

[0029] Preferably, the process comprises a first step of applying on at least one surface of the metal substrate a composition comprising a silicon compound, preferably a siloxane, more preferably a polysiloxane.

[0030] In a preferred embodiment the first composition comprises at least one siloxane, preferably a polysiloxane, more preferably dimethyl-polysiloxane. Preferably, the first composition comprises at least one siloxane in a concentration between 80 and 99% w / w (w / w) of the first composition, more preferably between 85 and 95% w / w.

[0031] In a preferred embodiment of the invention, the first composition comprises at least 85% w / w of the first composition of at least one siloxane, preferably at least 90% w / w.

[0032] The first composition preferably comprises at least one solvent known to the person skilled in the art, preferably at least one alcohol, more preferably ethanol.

[0033] Preferably, the first composition comprises at least one solvent in a concentration between 2 and 10% w / w (w / w) of the first composition, more preferably between 3 and 7% w / w.

[0034] In a preferred embodiment of the invention, the first composition comprises at least 3% w / w of the first composition of at least one solvent, preferably at least 4% w / w.

[0035] In a preferred embodiment, the first composition consists of at least one siloxane and at least one solvent as described in detail above.

[0036] The first composition is applied on at least one surface of the metal substrate by means of one of the techniques known to the person skilled in the art. Preferably, the application of the first composition is performed manually by at least an operator and / or is performed by a machine, for example by a robot. Preferably, the first composition is applied by spraying or by total or partial immersion of the metal substrate in the first composition. After the application of the first composition, preferably, there is a step of drying the metal substrate. The drying step takes place with techniques known to the person skilled in the art, preferably by oven drying and / or by ventilation.

[0037] In one embodiment, the drying step has a duration between 30 minutes and 120 minutes, preferably of about 60 minutes or until the metal substrate is completely dry, i.e. until the first composition has completely evaporated.

[0038] The application of the first composition is adapted to deposit a coating on at least one surface of the metal substrate, i.e. a deposit, preferably between 5 and 20 micrometers (pm), more preferably between 8 and 15 pm. In a preferred embodiment of the invention, the application of the first composition is adapted to deposit a coating on at least one surface of the metal substrate of about 10 pm.

[0039] The application of the first composition is adapted to give to the at least one metal substrate, preferably to at least one surface of the metal substrate, an improved hardness. The hardness values of the at least one metal substrate are assessed by the Rockwell (HR) test according to ISO 6508.

[0040] In one embodiment, the application of the first composition is adapted to give to the at least one metal substrate, preferably to a ferrous substrate, an improved hardness between 55 and 80 HRC, preferably between 60 and 75 HRC.

[0041] Preferably, the process comprises a second step of applying on at least one surface of the metal substrate a composition comprising a mixture of petroleum-derived hydrocarbons, preferably a mixture of petroleum distillates. Preferably, the mixture of hydrocarbons is obtained by treating a petroleum fraction with hydrogen in the presence of a catalyst.

[0042] Preferably, said second step takes place after the first step of the process, as described in details above.

[0043] In a preferred embodiment, the second composition comprises a mixture of hydrocarbons comprising or consisting of hydrocarbons with a carbon number predominantly in the range of C9 - C16 and with a boiling point between 130°C and 310°C, preferably between 150 and 290°C.

[0044] Preferably, the second composition comprises at least the mixture of hydrocarbons in a concentration between 80 and 99% w / w (w / w) of the second composition, more preferably between 85 and 95% w / w.

[0045] The second composition preferably comprises at least one solvent known to the person skilled in the art.

[0046] Preferably, the second composition comprises at least one solvent in a concentration between 2 and 10% w / w (w / w) of the second composition, more preferably between 3 and 7% w / w.

[0047] The second composition is applied on at least one surface of the metal substrate by means of one of the techniques known to the person skilled in the art. Preferably, the application of the second composition is performed manually by at least an operator and / or is performed by a machine, for example by a robot. Preferably, the second composition is applied by spraying or by total or partial immersion of the metal substrate in the second composition.

[0048] After the application of the second composition, preferably, there is a step of drying the metal substrate. The drying step takes place with techniques known to the person skilled in the art, preferably by oven drying and / or by ventilation.

[0049] In one embodiment, the drying step has a duration between 30 minutes and 120 minutes, preferably of about 60 minutes or until the metal substrate is completely dry, i.e. until the second composition has completely evaporated.

[0050] The application of the second composition is adapted to deposit a coating on at least one surface of the metal substrate, i.e. a deposit, preferably between 5 and 25 micrometers (pm), more preferably between 8 and 20 pm. In a preferred embodiment of the invention, the application of the second composition is adapted to deposit a coating on at least one surface of the metal substrate of about 15 pm. In one embodiment, the application of the second composition is repeated a plurality of times.

[0051] Preferably, two consecutive applications of the second composition on the metal substrate are adapted to deposit a coating on at least one surface of the metal substrate of about 20 pm.

[0052] Preferably, three consecutive applications of the second composition on the metal substrate are adapted to deposit a coating on at least one surface of the metal substrate of about 25 pm.

[0053] The application of the second composition is adapted to give to the at least one metal substrate an improved flowability and detachment capability. The values of flowability and detachment capability of the at least one metal substrate are assessed by means of an average roughness value (Ra) of the metal substrate. Said Ra value is assessed by a roughness meter, preferably with a digital roughness meter.

[0054] In one embodiment, the application of the second composition is adapted to give to the at least one metal substrate, preferably to a ferrous substrate, a roughness Ra < 0.5, pm preferably a roughness Ra < 0.4 pm.

[0055] Preferably, at the end of the application of the second composition, there is a step of dimensional verification of the deposit, preferably by means of a micrometer, preferably a digital micrometer (dualscope and / or gauge) and / or through a visual and microscopic verification of the deposit or with other techniques known to the person skilled in the art.

[0056] In one embodiment, prior to the application of the first and second composition, as described above, there are steps of preparing the metal substrate.

[0057] Preferably, in a first preparation step, the metal substrate is subjected to pickling / cleaning with techniques known to the person skilled in the art. Preferably, the metal substrate is inserted, preferably immersed, in a special tank containing an alkaline composition. Preferably, said alkaline composition comprises a solvent, for example water, in a concentration between 60 and 80%, preferably about 70% w / w, and an alkaline degreasing solution in a concentration between 20 and 40% w / w, preferably about 30% w / w.

[0058] In a preferred embodiment, the first preparation step takes place in an ultrasonic tank and at a temperature between 60 and 80°C, preferably between 65 and 75°C for a time between 30 and 90 minutes, preferably between 45 and 80 minutes.

[0059] In one embodiment, after the first preparation step, the metal substrate is subjected to a second preparation step. Preferably, the substrate is treated with an acid composition, preferably with an acid solution. Preferably, after treatment with the acid composition, the substrate is washed with water, preferably distilled water and then with a buffer solution to neutralize the previous treatment with the acid composition. Preferably, the buffer solution comprises at least 40% w / w of lime hydrate in a solvent, preferably in water. After treatment with the buffer composition, the substrate is washed with water, preferably distilled water. The second preparation step preferably takes place at a temperature between 10 and 25°C, preferably of about 20°C.

[0060] In one embodiment, after the first preparation step and / or after the second preparation step, the metal substrate is subjected to at least one polishing treatment with techniques known to the person skilled in the art. Preferably, the metal substrate is subjected to at least one mechanical polishing and / or electro-polishing and / or sandblasting treatment, preferably with silicon grains.

[0061] The Applicant has surprisingly developed a process suitable for giving greater hardness and flowability to metal substrates and for giving better resistance to wear and corrosion of the substrates without the use of hexavalent and trivalent chromium. In fact, the entire process described above in detail does not involve the use of chromium, in particular of neither hexavalent chromium nor trivalent chromium. Thus, such a process may entirely replace known electrolytic chromium plating processes, reducing, or zeroing, the environmental impact of such processes and markedly reducing the costs for the treatment of metal substrates. In addition, the waste derived from the process of the present invention is also very small and has a significantly reduced impact on the environment compared to the processes involving the use of chromium, in particular hexavalent chromium.

[0062] Finally, the times for the treatment of the metal substrates are also considerably reduced compared to the known chromium plating processes. In fact, the process of the present invention provides for a duration of about 3 hours, while an electrolytic chromium plating process has a duration of at least 5 hours.

[0063] A second aspect of the present invention concerns a metal substrate with at least one surface comprising at least one coating or layer.

[0064] Preferably, the metal substrate is obtained / obtainable with the process described in detail above.

[0065] In one embodiment, said metal substrate is a substrate comprising or consisting of a ferrous material or alloy. Preferably, the metal substrate is a ferrous substrate, more preferably it is a substrate comprising or consisting of a material selected from: iron, steel, preferably stainless steel, aluminum, copper and brass, and combinations thereof.

[0066] In one embodiment, said metal substrate is a metal substrate not limited by any shape, size or use.

[0067] Preferably, said metal substrate comprises on at least one surface thereof a first layer comprising at least one siloxane, preferably a polysiloxane, more preferably dimethyl polysiloxane. In a preferred embodiment, said first layer has a thickness between 5 and 20 micrometers (pm), more preferably between 8 and 15 pm. In a preferred embodiment of the invention, said first layer has a thickness of about 10 pm.

[0068] Preferably, at least one surface of the metal substrate has a hardness between 55 and 80 HRC, preferably between 60 and 75 HRC. The hardness values of the at least one metal substrate are assessed by the Rockwell (HR) test according to ISO 6508. io

[0069] In one embodiment, the metal substrate comprises on at least one surface thereof, a second layer or deposit comprising hydrocarbons with carbon number predominantly in the range of C9 - C16. The second layer has a thickness between 5 and 25 micrometers (pm), more preferably between 8 and 20 pm.

[0070] Preferably, at least one surface of the metal substrate has an average roughness Ra < 0.5, pm, preferably an average roughness Ra < 0.4 pm.

[0071] Said Ra value was measured by means of a roughness meter, preferably by means of a digital roughness meter.

[0072] EXAMPLE

[0073] Nanotechnological application process (ceramic-based) replacing thick hard electrolytic chromium plating for ferrous alloys.

[0074] The metal substrate to be treated is subjected, upon acceptance of the material, to dimensional check with a special digital micrometer (dualscope and / or gauge).

[0075] Following a dimensional check, the part was subjected to pickling / cleaning in a special ultrasonic tank containing 70% water and 30% alkaline degreasing solution at a temperature of 72°C. The part was immersed for 60 minutes.

[0076] At the exit from the alkaline treatment in the ultrasonic tank, the part was treated (automatically or manually) with Acid Solution (Acid Type BLK- AGEF), washed with distilled water at a temperature of 20°C, treated, for the neutralization of the previous acid wash, with buffer solution (50% water- 50% hydrated lime) and finally washed again with distilled water at 20° Celsius and dried with compressed air.

[0077] At the end of the previous step, the part was optionally subjected to mechanical polishing / electro-polishing or sandblasting treatment with silicon grains (size 2 microns) depending on the Customer's needs (polished or sandblasted effect of the part). Nanotechnological application

[0078] A first solution comprising dimethyl polysiloxane in a concentration higher than 85% by weight was applied on the metal substrate. The first solution gives a hardness between 65 and 72 HRC; this first application creates a deposit of 10 microns.

[0079] At the end of the application, the part was left for 1 hour in a special ventilated area for a complete drying of the treatment.

[0080] At the end of the drying, a second solution comprising a mixture of petroleum-derived hydrocarbons was applied to the metal substrate. The second solution gave a flowability and detachment capability measured as roughness of the substrate. The average roughness of the metal substrate was Ra< 0.4 pm.

[0081] The second solution created a deposit of 15 / 20 microns variable depending on the repetition of the application (Ex. 1 application 15 microns - 2 consecutive applications 20 microns - 3 consecutive applications 25 microns).

[0082] At the end of the application, the substrate was left for 1 hour in a special ventilated area for a complete drying of the treatment.

[0083] Finally, a dimensional verification of the deposit was made with a digital micrometer (dualscope and / or gauge); a visual and microscopic verification of the deposit.

[0084] Roughness detection by means of digital roughness meter after application of the first composition called "1 OHDIAM".

[0085] The detection highlighted the improvement in roughness, Ra 0.19, compared to the pre-treated mold which was Ra 1 .2.

[0086] Roughness detection by means of digital roughness meter after application of the second composition called "7HWS". The detection highlights that the application of the second product does not worsen the roughness obtained with the application of the first product (Ra 0.19).

[0087] Detection of the thickness of the second layer by means of digital micrometer.

[0088] The detection by means of digital micrometer highlights an overlay thickness equal 6.3 microns in overlap with the treatment of step 1 .

Claims

CLAIMS1 . A process for the deposition of at least one coating on at least one surface of a metal substrate comprising the steps of:- applying on at least one surface of the metal substrate a composition comprising a siloxane, and. - applying on the at least one surface of the metal substrate a composition comprising a mixture of petroleum-derived hydrocarbons, where the process does not involve the use of hexavalent chromium.

2. The process according to claim 1 , wherein the siloxane is a polysiloxane.

3. The process according to claim 2, wherein the polysiloxane is dimethyl polysiloxane.

4. The process according to any one of claims 1 to 3, wherein the first composition comprises at least one siloxane in a concentration between 80 and 99% w / w (w / w) by weight of the first composition, more preferably between 85 and 95% w / w.

5. The process according to any one of claims 1 to 4, wherein the hydrocarbon mixture comprises hydrocarbons having carbon numbers in the range of C9 - C16.

6. The process according to any one of claims 1 -5, wherein the hydrocarbon mixture comprises hydrocarbons having a boiling point between 130°C and 310°C, preferably between 150°C and 290°C.

7. A metal substrate with at least one surface area comprising a first layer comprising at least one siloxane and a second layer comprising hydrocarbons having carbon numbers in the range of C9 - C16.

8. The metal substrate according to claim 7, wherein the at least one surface of the metal substrate has a hardness between 55 and 80 HRC, preferably between 60 and 75 HRC, wherein the hardness is assessed by the Rockwell (HR) test according to ISO 6508.

9. The metal substrate according to claim 7 or 8, wherein the at least one surface of the metal substrate has an average roughness Ra < 0.5, pm, preferably an average roughness Ra < 0.4 pm wherein the roughness is assessed with a digital roughness meter.

10. The substrate according to any one of claims 1 -9, wherein the first layer has a thickness between 5 and 20 micrometers (pm), more preferably between 8 and 15 pm, and wherein the second layer has a thickness between 5 and 25 micrometers (pm), more preferably between 8 and 20 pm.1 1 . The metal substrate according to any one of claims 7-10, wherein said metal substrate is obtained by the process according to any one of claims