Abstract: Invasive medical catheters with distal end assemblies having a protective surface coating bonded thereto are constructed by applying a hydrophilic primer to at least a portion of a tubular polymer body. The primer coating chemically bonds to the polymer substrate by developing covalent bonding or cross linking with the substrate. A plurality of printed electrode elements are then formed on the polymer body, e.g., by a pad printing process. Once the primer coating is bonded to the polymer body, the assembly is coated with a regenerated cellulose layer, e.g., by a viscose process well known in the art. The primer coating, already bonded to the catheter body, is then bonded with the regenerated cellulose at an elevated temperature. After curing, the polymer body, primer coating and regenerated cellulose layer become a single composite material, thereby preventing the regenerated cellulose coating from any movement relative to the polymer body, and providing a secure protective layer over the electrodes.