Rubber reinforcing steel cord, manufacturing method of rubber reinforcing steel cord and pneumatic tire

A pneumatic tire comprising rubber-based structural elements and a reinforcing steel cord formed from a treated steel wire as a reinforcing element, wherein the treated steel wire consists essentially of a steel wire plated with metal containing copper having applied on the surface thereof an oil containing a cobalt compound, wherein the concentration of the cobalt compound in the oil is 0.3 to 10.00 mass percent.

A method of manufacturing a rubber reinforcing steel cord, comprising:

• the application step of applying oil containing a cobalt compound to a steel wire plated with metal containing copper, wherein the concentration of the cobalt compound in the oil is 0.3 to 10.0 mass percent, and
• the step of twisting at least one of said steel wires.

A method of manufacturing a pneumatic tire which comprises:

• applying an oil composition to a steel wire plated with metal containing copper after all drawing operations performed on the steel wire to form a treated steel wire, wherein the oil composition consists essentially of oil and a cobalt compound, and wherein the concentration of the cobalt compound in the oil is 0.3 to 10.0 mass percent;
• and
• incorporating the treated steel wire into a pneumatic tire as a reinforcing element.