Convention state may grant other maritime liens on a vessel to secure claims in addition to those referred to in Article 4 subject to various provisos which rank in priority after the Convention maritime liens and registered mortgages, hypotheques or charges (complying with Article 1). The 1993 Convention sets out the various priorities between Convention maritime liens (under Article 4), other maritime liens (under Article 6), mortgages and rights of retention. The order of priority is, Convention maritime liens, rights of retention in favour of ship repairers or shipbuilders, registered mortgages, hypotheques and charges and other maritime liens. With regard to maritime liens, salvage has priority over all other maritime liens which have attached to the vessel prior to the time when the operation giving rise to the said liens were performed. Salvage liens rank in reverse order of the time when the claims secured thereby accrued. The other liens rank in the order listed above but as between themselves rank pari passu. Other maritime liens under Article 6 rank after the maritime liens set out in Article 4 and also after registered mortgages, hypotheques or charges which comply with the provisions of Article 1. These liens are extinguished after a period of six months from the time when the claims secured by them arose or at the end of a period of 60 days following a sale to a bona fide purchaser of a vessel.