KTL is the abbreviation for the German term "kathodische Tauchlackierung", which means cathodic dip coating. This is an electrochemical process in which the workpiece is coated in a dipping bath. The process is used for coating complicated structures and large numbers of parts (source of German text: Wikipedia). In surface drainage, ductile iron gratings with cathodic dip coating are used amongst others. These have better corrosion-resistance.