METHOD FOR COATING METAL

Abstract

A metal substrate with a silicon oxide based layer having a thickness between 80 and 400 nm and having between 5 and 30 atom % of carbon. Also included is a process for depositing by PECVD a silicon oxide based layer, having a thickness comprised between 80 and 400 nm and comprising between 5 and 30 atom % of carbon, on a metal substrate.

Claims

1. A metal substrate comprising: a silicon oxide based layer having a thickness comprised between 80 and 400 nm and comprising between 5 and 30 atom % of carbon.

2. The metal substrate according to claim 1, further comprising an anodized metal layer in between a bulk metal and the silicon oxide based layer.

3. The metal substrate according to claim 1, wherein the silicon oxide based layer comprises at least 80% by weight of SiO2.

4. The metal substrate according to claim 1, wherein the silicon oxide based layer comprises up to 15% by weight of titanium oxide, zirconium oxide or a mixture of titanium oxide and zirconium oxide.

5. A method for the production of a silicon oxide based layer, having a thickness comprised between 80 and 400 nm, comprising between 5 and 30 atom % of carbon, on a metal substrate, comprising: a. taking a low-pressure PECVD device comprising at least one linear dual-beam plasma source, wherein the linear dual-beam plasma source comprises at least two electrodes connected to an AC or pulsed DC generator, for the deposition of said layers on the substrate; b. applying an electrical power between the two electrodes, so that the power density of the plasma is between 3 and 17 W per cm2 of plasma; and c. applying, to the substrate, a gaseous carbon-comprising precursor of silicon oxide at a flow rate of between 125 and 750 sccm per linear meter of the plasma source and a reactive gas based on oxygen or on oxygen-comprising derivatives at a flow rate of between 500 and 2500 sccm per linear meter of the plasma source.

6. A method for the production of a silicon oxide based layer, having a thickness comprised between 80 and 400 nm, comprising between 5 and 30 atom % of carbon, on a metal substrate, comprising: a. taking a low-pressure PECVD device comprising at least one hollow-cathode plasma source, wherein the hollow-cathode plasma source comprises at least one electrode connected to an AC, DC or pulsed DC generator, for the deposition of said layers on the substrate; b. applying an electrical power to the plasma source, so that the power density of the plasma is between 10 and 50 kW per meter of plasma; and, c. applying, to the substrate, a gaseous carbon-comprising precursor of silicon oxide at a flow rate of between 125 and 750 sccm per linear meter of the plasma source and a reactive gas based on oxygen or on oxygen-comprising derivatives at a flow rate of between 550 and 2500 sccm per linear meter of the plasma source.

Description

DESCRIPTION OF EMBODIMENTS

[0068] Metal strips of an aluminum were coated with a dual-beam hollow cathode PECVD source having a length of 40 cm.

[0069] The precursor used was TMDSO. The metal substrate was transported at a continuous speed on a roller conveyor beneath the PECVD source in a direction transversal to the length of the source. Deposition parameters are given in Table 1 below.

TABLE-US-00001 TABLE 1 Precursor O2 flow Substrate Number Power flow rate Pressure rate speed of [kW] [sccm] [mTorr] [sccm] [m/min] passes Ex 1 16 35.7 11 1918 0.5 2 Ex 2 16 95  7 1200 0.7 1 Ex 3  5 110 15 2400 1.5 2 Cex 1  5 54 11 1900 0.16 2 Cex 2 16 87  7 1918 8 2 Cex 3 20 110 15 2400 2 2

[0070] As can be seen from table 2 below, the resulting coated aluminium strips were subjected to the corrosion test described above and inspected visually. Furthermore the gloss before and after the corrosion test was measured and the difference determined. The coated metal strips were then submitted to heating under air at a temperature of 100° C. for 60 minutes and visually inspected for defects.

TABLE-US-00002 TABLE 2 Defects Thickness Corrosion Gloss upon [nm] visual difference heating Ex 1 300 Ok  <5% No Ex 2 280 Ok <10% No Ex 3 200 Ok  <5% No Cex 1 800 Ok  <5% Yes Cex 2  50 KO >10% No Cex 3 200 KO >10% No

[0071] Examples Ex1, Ex2, and Ex3 and counter examples Cex 1, Cex 2 presented a carbon content comprised between 5 and 30 at %. Carbon content can for example be determined by XPS analysis. These samples presented good resistance to corrosion, showing non visible change a less than 10% change in gloss.

[0072] Counterexample Cex 3 presented a carbon content of less than 1 at %.

[0073] Examples of anodized aluminium were coated in the same way as examples Ex1, Ex2, Ex3 and presented similar results, but furthermore could be exposed to pH 13.5 solution in the corrosion for at least 20 minutes without any visible deterioration.