Tube fitting and tube equipped with tube fitting

A tube fitting that is capable of coupling a tube made from metal and provided with an annular portion upon an end portion thereof, to a mating member by being installed upon an external periphery of the tube and by being fastened to the mating member in a state of contacting the annular portion, the annular portion projecting in a radially outward direction from the tube,

• the tube fitting comprising:
• a threaded portion upon which is formed an external thread that engages with an internal thread provided in the mating member;
• a contact portion that is provided at an end portion of the tube fitting in a direction of progression of the external thread when the tube fitting is being fastened, and that, when the tube fitting is fastened to the mating member, contacts the annular portion to press the annular portion against the mating member;
• and
• a resin coating layer provided over a coated region that includes surfaces of the threaded portion and the contact portion;
• and wherein:
• a through hole extending in a direction parallel to the direction of progression is pierced through both the threaded portion and the contact portion;
• the external thread has an outer diameter of 9.53 to 14.0 mm, and the contact portion has an inner diameter of 4.98 to 8.44 mm;
• the resin coating layer includes a polyethylene based substance, a lubricant, and solid particles;
• a thickness of the resin coating layer is not uniform throughout the coated region;
• and when mass per unit area w (g/m2) is defined as being a value obtained by dividing a mass difference between a state with the resin coating layer and a state without the resin coating layer by a surface area of the coated region,
• the mass per unit area w satisfies a relation 0.79<w<10.07.