Cleaned all my positiive wires and dialectic greased them. Four days later they;re corroded again. Could this be a weak alternator? The battery is only one year old.

 

In my experiences these are the best bet going for keeping terminals clean. I installed the Mopar orbital batteries in mine after I got tired of baby sitting the batteries. With the heat of the summer I was cleaning them nearly once a week and still getting build up on the terminals. They stay nice and clean now. I've have customers that have had them in over two years and they are clean as can be. Expensive, but worth it in my eyes.