Surface treated steel sheet for fuel tank

A surface treated steel sheet for a fuel tank, the surface treated steel sheet comprising:

• a Zn plated layer or a Zn—Ni alloy plated layer which is placed on a surface to be an inner surface of the fuel tank, the surface being a base metal, or on the surface to be the inner surface of the fuel tank and a surface to be an outer surface of the fuel tank, the surface being the base metal;
• and
• a chromate-free chemical conversion coating layer containing a water-and-oil repellent, the chromate-free chemical conversion coating layer being placed over the Zn plated layer or the Zn—Ni alloy plated layer,
• wherein a water contact angle on a surface of the chromate-free chemical conversion coating layer is more than or equal to 70 degrees and an n-hexadecane contact angle on the surface of the chromate-free chemical conversion coating layer is more than or equal to 30 degrees and less than or equal to 70 degrees.