A housing for a spark plug. The housing includes a bore along the longitudinal axis X of the housing, as the result of which the housing has an outer side and an inner side, and an electroplated or chemically applied nickel-containing protective layer situated on at least one portion of the outer side of the housing and a sealing layer situated on the nickel-containing protective layer. The sealing layer contains silicon. A first intermediate layer is applied between the housing and the nickel-containing protective layer and/or a second intermediate layer is applied between the nickel-containing protective layer and the sealing layer and/or a cover layer is applied on the sealing layer. The sealing layer may be free of chromium.

A housing for a spark plug. The housing includes a bore along the longitudinal axis X of the housing, as the result of which the housing has an outer side and an inner side, and an electroplated or chemically applied nickel-containing protective layer situated on at least one portion of the outer side of the housing and a sealing layer situated on the nickel-containing protective layer. The sealing layer contains silicon. A first intermediate layer is applied between the housing and the nickel-containing protective layer and/or a second intermediate layer is applied between the nickel-containing protective layer and the sealing layer and/or a cover layer is applied on the sealing layer. The sealing layer may be free of chromium.

Disclosed is an electrode including a rhodium alloy, wherein the rhodium alloy includes rhodium and nickel. The alloy includes a greater quantity of rhodium as compared to any other individual element of the alloy.

Disclosed is an electrode including a rhodium alloy, wherein the rhodium alloy includes rhodium and nickel. The alloy includes a greater quantity of rhodium as compared to any other individual element of the alloy.

Disclosed is a rhodium alloy including: rhodium; one or more elements selected from the group consisting of iridium, platinum, palladium and ruthenium; and one or more elements selected from the group consisting of yttrium, zirconium and samarium. The alloy includes a greater quantity of rhodium as compared to any other individual element of the alloy. Also disclosed is an electrode, as well as a spark plug, including the claimed rhodium alloy.

Disclosed is a rhodium alloy including: rhodium; one or more elements selected from the group consisting of iridium, platinum, palladium and ruthenium; and one or more elements selected from the group consisting of yttrium, zirconium and samarium. The alloy includes a greater quantity of rhodium as compared to any other individual element of the alloy. Also disclosed is an electrode, as well as a spark plug, including the claimed rhodium alloy.

An ignition plug includes an insulator that includes a through hole; a center electrode; a metal shell that holds the insulator; a bar-shaped ground electrode body; an electrode tip that is disposed along a side surface of the ground electrode body opposing a discharge surface of the center electrode; and a welding portion that is disposed between the ground electrode tip and the ground electrode body. Over 1/4 of a range from a first end to a second end of the ground electrode tip, a length L1 of the ground electrode tip and a length L2 of the welding portion in the direction satisfy (L2/L1) ≧0.25.

An ignition plug includes an insulator that includes a through hole; a center electrode; a metal shell that holds the insulator; a bar-shaped ground electrode body; an electrode tip that is disposed along a side surface of the ground electrode body opposing a discharge surface of the center electrode; and a welding portion that is disposed between the ground electrode tip and the ground electrode body. Over 1/4 of a range from a first end to a second end of the ground electrode tip, a length L1 of the ground electrode tip and a length L2 of the welding portion in the direction satisfy (L2/L1) ≧0.25.

A spark plug includes a ceramic insulator having an axial hole formed in an axis direction of the spark plug, a center electrode inserted in a front side of the axial hole, a metal shell disposed around the ceramic insulator and a ground electrode joined to a front end portion of the metal shell, wherein the ground electrode has a cross-sectional area of 2.0 mm.sup.2 or smaller in any arbitrary cross section thereof taken in a direction perpendicular to a center line of the ground electrode; the ground electrode is made of a metal material containing 93 mass % or more of nickel; and the ground electrode has a Vickers hardness of 130 to 260 Hv.

A spark plug includes a ceramic insulator having an axial hole formed in an axis direction of the spark plug, a center electrode inserted in a front side of the axial hole, a metal shell disposed around the ceramic insulator and a ground electrode joined to a front end portion of the metal shell, wherein the ground electrode has a cross-sectional area of 2.0 mm.sup.2 or smaller in any arbitrary cross section thereof taken in a direction perpendicular to a center line of the ground electrode; the ground electrode is made of a metal material containing 93 mass % or more of nickel; and the ground electrode has a Vickers hardness of 130 to 260 Hv.