Good quality deck hardware of stainless steel or chrome is highly resistant to corrosion and the marine environment, but it still needs some maintenance if you want to keep it looking good. Make sure you offer this service if you notice small streaks of surface corrosion due to oxidation of the fasteners. This type of corrosion can be easily removed with a good metal polish. After you are done, protect it with a light coat of marine wax or a light coat of moisture displacing corrosion resistant lubricant. The wax will last longer. On aluminum fittings, polish until the applied polish turns black. Sprinkle Arm & Hammer baking soda on a rag and wipe the black right off or use mineral spirits and squirt it on and wipe it off.
Believe it or not, if you use a lemon peel, it will cut down on grime that other cleaners miss. If you think that is too strong use lemon oil that you use on cabin furniture as a substitute for stainless steel cleaner. Rubbing alcohol also works on stainless steel. When cleaning aluminum look for a grain direction. If you look close you will see it. Rub with the grain. Real bad stains can be rubbed with the shiny side of aluminum foil. Do not polish aluminum when it is 50º F or less outside as it may scratch. Do not use cleaners containing ammonia such as window cleaner as they can cause pitting.
Silver polish works fabulous on aluminum. For brass, go cheap. One tablespoon of flour, one tablespoon of salt and one tablespoon of vinegar. Apply the powder mixture with a clean damp rag and wipe off the tarnish and shine. Wash with soapy water later. If it’s a tough stain, cut a lemon in half, dust the cut end with baking soda and rub on small sections at a time. The baking soda adds the necessary mild abrasive to scrub your brass back to life. You may also use Nev-R-Dull a canister of presoaked wading which can be used to polish the aluminum and metal or Magic Mix from Valco Products in Cincinnati, OH.