A partial award that partially decides the merits of the dispute may be immediately challenged under Article 827, paragraph 3 of the Code of Civil Procedure, but only when it has determined the proceedings in relation to one or more claims by deciding them. A non-final award that resolves preliminary questions of merit or procedural preliminary issues without ending the arbitral proceedings may be challenged only together with the final award.
In arbitral proceedings, the question whether the arbitration agreement exists or is valid is a procedural preliminary matter, since it determines whether the arbitrators have power to decide. It may be the subject of a non-final award that cannot be immediately challenged.
For a partial award to be independently challengeable, the only test is whether the award has determined the proceedings wholly or partly, regardless of whether the questions dealt with are procedural or substantive, given that the award may be enforceable in such cases.