Maybe clean it up and apply Duralac or Tefgel.

Does JB Weld have iron filings in it? If it does, will you get Galvanic corrosion if you apply it to Aluminium?

I've just spent many hours cleaning aluminium window frames of goo and white powder from the Galvanic action between the frames and stainless steel fixing screws. I'd consider using JB Weld to repair the holes the screws screw into in the aluminium frame, but I'd like to know if it will set off a Galvanic reaction before I do.

keensailor said..
Whilst replacing water pump assembly I noticed this 10mm wide pit. It is not causing an issue "yet" as this area sits under the impeller base plate. Wondered if there is anything that could be done at this stage before it eats a hole right through casting. The anode looks alright but maybe I should be replacing that as well.

The following may be of interest in case you do not frequent pure salt water.

( Plagiarising a post here: www.macgregorsailors.com/forum/viewtopic.php?f=9&t=27528&hilit=anodes )

Zinc Alloy Anodes = Salt water only
Not recommended for use in fresh water

Aluminum Alloy Anodes = Salt or Brackish water
Not recommended for use in fresh water
Proven to last longer than zinc due to increased capacity

Magnesium Alloy Anodes = Fresh water only
Not recommended for use in salt or brackish water
The only alloy proven to protect your boat in fresh water

Here's a resource I found for anodes. These guys seem to know their stuff. martyranodes.com/
Catalog:
http://martyranodes.com/sites/default/f ... AT19_0.pdf