Casing for an electrical component

1. A casing for encapsulation of an electrical component, comprising an outer layer of a semipermeable material and an inner layer comprising a chemically active, hydrophilic substance that chemically combines with water to form a compound.

2. A casing as claimed in claim 1 , wherein the outer layer is flexible.

3. A casing as claimed in claim 1 , wherein the inner layer comprises a metal oxide powder.

4. A casing as claimed in claim 1 , wherein the inner layer comprises a loose metal oxide powder, a metal oxide powder within a matrix or a metal oxide powder in a breathable bag.

5. A casing as claimed in claim 1 , wherein the inner layer comprises a solid metal oxide.

6. A casing as claimed in claim 1 , wherein the inner layer comprises a metal film.

7. A casing as claimed in claim 1 , wherein the inner layer comprises a plurality of metal films.

8. A casing as claimed in claim 1 , wherein at least one polymer film is provided adjacent to at least one metal film.

9. A casing as claimed in claim 3 , wherein the metal oxide is Calcium oxide.

10. A casing as claimed in claim 3 , wherein the metal is Calcium.

11. A casing as claimed in claim 1 , wherein the outer layer is made from a fluorinated polymer.

12. A casing as claimed in claim 1 , wherein the chemically active substance comprises a metal from group 1 or group 2 of the Periodic Table or an oxide of a metal from group 1 or group 2 of the Periodic Table.

13. A casing as claimed in claim 1 , wherein the electrical component is a piezoelectric actuator.

14. A casing as claimed in claim 1 , further comprising an insulating layer between said electrical component and said hydrophilic substance.

15. A casing as claimed in claim 14 , wherein said insulating layer is a polymer.