Cleaning Zincs

[TADTOOMUCH]

The zincs on my propeller shafts and trim tabs are in good shape but have a white/tan layer of crust on them. Is this zinc oxide? Should I clean this off before I launch it or should I just launch it and leave it on?
Seems that the layer would protect the zinc from getting in good contact with the water and negate the reason for having them.

I tried to wire brush them but it didn't do much. Is there a way to dissolve this oxide layer so fresh unoxidized zinc is in contact with the water?

[Stripermann2]

I'm not sure I would worry too much if they are still whole and in good shape. It's most likely from being exposed to air that you see the crustation of the zinc.

[TADTOOMUCH]

The more I read, the more I think I have zinc anodes on my boat instead of magnesium.

They have been on the boat for four years with very little corrosion and have a good layer of oxide on them.

In fresh water I should have magnesium anodes and they should not have a built up layer on them and they should not last this long.

I will just remove what I have and replace with what are known to be magnesium for fresh water. The cost is not that much compared to a new propeller, rudder, shaft or trim tab.

[Big D]

If they've been on there for four years in fresh water, they are zinc. Yes, you should be using magnesium. Magnesium is more expensive but protects better in fresh water. However, it builds up a layer on it caused by a chemical reaction that will render it inefficient after one season. That and the fact it sacrifices metal easier than zinc means you will have to replace magnesium anodes every season. Zinc by the way also gets a coat on it but it takes longer and eventually doesn't protect anymore. It usually has a slight yellow tinge. I always like hearing from those that say "my anodes have lasted for years", that just means they're not doing they're job or there isn't a corrosion problem...yet!! I've seen hardware corrode right off and the anodes look perfect; they simply weren't doing the job anymore. If you switch to mag, you must switch all of them on the boat. If you are in a marina with a boat on either side of you that are using zinc instead, I recommend talking them into switching as well. Tell them the benefits. If they don't, your new mag ones will be working overtime.