Noting that the corrosive properties of some goods will vary depending whether or not it is exposed to steel or aluminium the correct interpretation should be that sheets of both aluminium and steel are used in the test . The justification for this position is that aluminium is used in the construction of airframes and is increasingly being applied in shipbuilding , particularly in large high speed Roll On- Roll Off ( RO-RO ) and Roll On-Roll Off Passenger ( RO PAX ) vessels .