Here are several ways to prevent galvanic corrosion on aluminum boats and pontoons:

• Copper causes galvanic corrosion, which destroys aluminum. Only apply copper-free bottom paint, copper-free topside paint, copper-free primer or copper-free prop paint designed for aluminum.
• Do not paint anodes or grounding plates.
• Avoid contact with dissimilar metals.
• Electrically isolate all fittings- even on small boats.
• When protecting aluminum, do not exceed 1,000 minivolts of impressed current voltage.
• Do not use an automotive battery charger aboard a boat - especially one made of aluminum.
• After boating in salt water, always rinse aluminum surfaces thoroughly with fresh water.
• For adding hardware, use aluminum or 300-series stainless steel fasteners & fittings with plastic washers. 
• Applying LanoCote or Tef-Gel to fasteners also helps prevent corrosion.