They will be anodised aluminium. Unless you went with Chrome.
Use a product called 'flitz', Bill of Monster Tower put me onto it originally for cleaning towers and tower bits - it kicks ass and leaves a msear free, water repelleing shield when you're done. it also works a treat on all fibreglass so is a great product to have in the boat.
http://www.flitz.com/index.html - check to their metal and fibreglass polish. A tube (only $10!)will easily last close to a seasons use... makes for an absolute bargain!!