Aluminium enclosures may offer already some EMC reduction under certain circumstances, on account of their material. However, the joints (tongue and groove) need to be fitted with the appropriate seals for optimal EMC applications, and it must be taken into consideration that the lacquer coatings will have to be bridged. This can be done with the appropriate seals or by removing the coating of lacquer. The amount of work involved must be made clear when your requirements are specified.