on the market that are suppose to be superior for some reason or the other. I suppose there might be some component or the other that might retard corrosion to some small degree or another but the bottom line based on my 39 years working for a huge public utility company is that any thick grease will work just fine. There are some specialty greases that some of the high voltage equipment manufactures want you to use in certain applications but 99% of all electrical connections are made up with axle grease from Chevron or Shell oil that we bought in 5 gallon buckets. These connections were for anything from 12 to 132 volt DC to 220 to 500 thousand volts AC and everything in between. The specialty greases were used usually in in conjunction with gas insulated switchgear where exotic gasses would react with normal grease. These gasses, mostly Sulfur Hexafluoride six or SF-6, are used as a dielectric in 66K(v) voltages equipment and above. So, IMHO, you can spend anything you want. Some may be more convenient or cleaner to use then others but for protecting a 12DC or 130AC connection on a boat plane old axel grease will work just fine. Clean the connection with a wire brush, sand paper or Scotch Bright pad, greases it up before it gets a chance to oxidize and make up the connection. A LITTLE painted over the terminals might help keep any moisture out as well if you feel the need. I don't use additional grease over my connections. I use both waterproof axel grease and Dow Corning 111 silicone grease. The axel grease is easier to clean up with mineral spirits but the 111 comes in a very handy tube.