Iron-based piping element for buried pipeline, comprising an outer coating

1. An iron-based piping element for a buried pipeline in a soil, comprising a raw piping element and an outer coating, the raw piping element comprising a metal wall, wherein the outer coating comprises:

a first layer situated on the raw piping element and comprising at least one porous layer of zinc/aluminum alloy containing 5 to 60 wt % of aluminum;

a second layer of adhesive situated on the first layer; and

a third layer situated on the second layer and comprising a synthetic organic material, the third layer forming a sealed barrier between the metal wall of the raw piping and the soil,

wherein the second layer of adhesive provides a mechanical link between the first layer and the third layer,

wherein the third layer forming a sealed barrier prevents any contact between the metal wall of the raw piping element and water from the soil, and

wherein the second layer and the third layer consist of different material compositions.

2. The piping element according to claim 1 , wherein the first layer is made up of said porous layer of zinc/aluminum alloy.

3. The piping element according to claim 1 , wherein the first layer further comprises a layer of sealant paint situated between the porous layer of zinc/aluminum alloy and the second layer.

4. The piping element according to claim 1 , wherein the second layer comprises a holtmelt glue.

5. The piping element according claim 1 , wherein the second layer includes an anticorrosion pigment and/or a bactericidal agent.

6. The piping element according claim 1 , wherein the second layer is provided without metal components.

7. The piping element according to claim 1 , wherein the synthetic organic material comprises polyethylene, for example bimodal high-density polyethylene, or comprises polypropylene.

8. The piping element according to claim 1 , wherein the synthetic organic material comprises polyethylene or polypropylene reinforced by hard mineral fillers.

9. The piping element according to claim 1 , wherein the third layer includes a coloring agent imparting a maximum contrast to the piping element with respect to the color of the soil in which the piping element is intended to be buried.

10. A buried pipeline comprising piping elements according to claim 1 .

11. An iron-based piping element according to claim 1 , wherein the third layer has a thickness comprised between 1 mm and 5 mm.

12. An iron-based piping element according to claim 1 , wherein the raw piping element is made from cast iron.

13. An iron-based piping element for a buried pipeline in a soil, comprising a raw piping element and an outer coating, the raw piping element comprising a metal wall, wherein the outer coating comprises:

a first layer situated on the raw piping element and comprising at least one porous layer of zinc/aluminum alloy containing 5 to 60 wt % of aluminum;

a second layer of adhesive situated on the first layer, the adhesive selected from the group consisting of a hot-melt glue having a base of a vinyl ethylene-acetate copolymer and a hot-melt glue having a base of an ethylene-acrylate copolymer; and

a third layer situated on the second layer and comprising a synthetic organic material, the third layer forming a sealed barrier between the metal wall of the raw piping and the soil, the third layer selected from the group consisting of a polyethylene-based resin and a polypropylene-based resin,

wherein the second layer of adhesive provides a mechanical link between the first layer and the third layer,

wherein the third layer forming a sealed barrier prevents any contact between the metal wall of the raw piping element and water from the soil.

14. The piping element according to claim 13 , wherein the first layer is made up of said porous layer of zinc/aluminum alloy.

15. The piping element according to claim 13 , wherein the first layer further comprises a layer of sealant paint situated between the porous layer of zinc/aluminum alloy and the second layer.