To provide a flexible composite laminate that forms a cover strip of a secondary cryogenic sealing barrier for a tank containing liquid methane, and a process for assembling by bonding, a secondary barrier comprising strips of this flexible laminate bonded to the joints of another subjacent composite laminate.

The flexible laminate 9 is bonded to the joint of adjacent composite panels covered with subjacent laminates 7 and includes a metal foil inserted between two fabrics impregnated with a binder. The flexible laminate 9 is pre-spread with a hot-melt adhesive 208 and, to give an assembly subsequently obtained, via the curing, by heating and under pressure, of the adhesive in contact with the subjacent laminates, in particular improved mechanical strength and protection against leaks of cryogenic liquid, the hot-melt adhesive 208 is applied at the softening point of the adhesive to that of the fabrics 9a of the flexible laminate which is intended to cover each subjacent laminate and to at least one peripheral edge 115 of the flexible laminate.