1. The use of a carbonaceous coating for protection of a passive electrical component from attack by ammonia, wherein the carbonaceous coating (i) is a sol-gel coating or (ii) is a plasma-polymeric coating and in each case comprises a carbon content, measured at a depth of 80 nm away from the side of the coating remote from the component, of 50 to 100 atom%, preferably 50 to 90 atom%, or, as an organometallic coating, comprises a carbon content of 2 to 50 atom%, in each case measured by XPS and based on the atoms detected by XPS.
2. The use as claimed in claim 1, wherein the carbonaceous coating, measured at the surface of the side of the coating remote from the component, based on the total carbon content, measured by XPS at this surface, comprises (i) ≤ 15 atom% for sol-gel coatings or (ii) ≤ 10 atom% for plasma-polymeric coatings of carbon as constituent of hydrolyzable groups.
3. The use as claimed in claim 1 or 2, wherein the carbonaceous coating is an aCH coating or an organosilicon coating.
4. The use as claimed in any of the preceding claims, wherein an interlayer is disposed between the electrical component and the carbonaceous coating.
5. The use as claimed in claim 4, wherein the interlayer is selected from the group of the ceramic layers, preferably based on TiO2, SiO2, Al2O3, TixNy or BN, and is further preferably an eloxal layer.
6. The use as claimed in any of the preceding claims, wherein the surface of the component consists of copper, aluminum or an alloy comprising copper and/or aluminum.
7. The use as claimed in any of the preceding claims, wherein the component is a coil, a resistor or a capacitor.
8. The use as claimed in any of the preceding claims, wherein carbonaceous coating

- comprises silicon and/or
- has an elongation at break of ≥ 2.5% and/or

- has a hardness measurable by nanoindentation in the range from 2 to 6 GPa, preferably 3.1 to 6 GPa, and/or
- comprises proportions determinable by measurement by XPS, measured at a depth of 80 nm away from the side of the carbonaceous, especially plasma-polymeric, coating remote from the interlayer, 5 to 40 atom%, preferably 20 to 32 atom%, of silicon and/or 30 to 70 atom%, preferably 40 to 64 atom%, of oxygen, based on the total number of carbon, silicon and oxygen atoms present in the coating, and/or
- has a thickness of 100 nm to 100 µm, preferably 200 nm to 50 µm and further preferably 500 nm to 10 µm.
9. The use as claimed in any of the preceding claims, wherein an interlayer is
disposed between the electrical component and the carbonaceous coating and
wherein the interlayer
- contains a crosslinked and/or uncrosslinked oil and/or crosslinked and/or uncrosslinked silicone oil, and/or a zone of crosslinked oil or crosslinked silicone oil is present between the interlayer and the carbonaceous layer, and/or
- together with the carbonaceous plasma-polymeric coating has a dielectric strength measured to DIN EN 60243-1 and DIN EN 60243-2 of ≥ 100 V measured up to a maximum current flow of 3 mA.

10. A system intended for contact with ammonia or ammoniacal media, comprising a passive electrical component having a carbonaceous coating as defined in any of the preceding claims, and optionally having an interlayer as defined in any of claims 4, 5 and 9, disposed in a region of the system intended for direct contact with ammonia or ammoniacal media.
11. The system as claimed in claim 10, wherein the system is a cooling apparatus or a plant for production, for processing, for use, for transport or for storage of ammonia or ammoniacal media.