Welded joint and automobile member

A welded joint comprising a first steel sheet, a second steel sheet, and a spot welded part joining the first steel sheet and the second steel sheet, wherein

• a first plating layer is provided on a surface of the first steel sheet facing the second steel sheet,
• no plating layer is present on or a second plating layer is provided on a surface of the second steel sheet facing the first steel sheet,
• the spot welded part has a nugget and a corona bond,
• a boundary plating layer is provided between the first steel sheet and the second steel sheet, from an end part of the corona bond to 0.5 mm from the end part of the corona bond toward an outside of the spot welded part,
• a Zn penetrated part is present at least at one of the first steel sheet or the second steel sheet adjoining the boundary plating layer,
• the Zn penetrated part advances from the boundary plating layer along a steel grain boundary, the Zn penetrated part comprising a first part in direct contact with the boundary plating layer and a front end in a direction away from the boundary plating layer and not in direct contact with the boundary plating layer,
• an Mg concentration at the front end of the Zn penetrated part, at a location where a Zn concentration is 0.1 mass %, is 0.20 mass % or less, and
• the first plating layer and the second plating layer satisfy the following Relation I:
• 0.010≥[(Mg composition of the first plating layer (mass %))×(amount of deposition of the first plating layer (g/m2))+(Mg composition of the second plating layer (mass %))×(amount of deposition of the second plating layer (g/m2))]/[(Zn composition of the first plating layer (mass %))×(amount of deposition of the first plating layer (g/m2))+(Zn composition of the second plating layer (mass %))×(amount of deposition of the second plating layer (g/m2))]≥0.001 Relation I:
• where, if no second plating layer is present, the Mg composition, Zn composition, and amount of deposition of the second plating layer are 0.