How can i fix my zanussi dishwasher model ds16tcr?

my dishwasher is working fine, apart from when it is on the drying cycle. The element seems to be overheating and smells
of burning, The dishwasher was leaking when it filled up,so we replaced the leaking pump hose. The heating element now has a lot of brown looking scale on it, I think this is what is burning. Is there anything that can be put in the dishwasher to remove the hard water scale? we have just bought this dishwasher second hand. Can you please help. Thank you.