Home Postcode finder SA Black Rock Black Rock postcode SA Black Rock is a locality in South Australia covered by postcode 5431. Postcode 5431 State or territory South Australia (SA) Region SA Outer Suburbs Add a free Black Rock business listing Be the first listing in Black Rock Common questionsWhat is the postcode for Black Rock?Black Rock, SA has the postcode 5431.What state is Black Rock in?Black Rock is in South Australia (SA).Does postcode 5431 cover more than one suburb?Yes. Postcode 5431 covers 14 localities, so the postcode alone does not identify Black Rock. Browse other postcodes in South Australia, or widen the search to every Australian postcode.