Is this zinc still ok to use

[captstu]

Two things :

1. If the zinc is not corroded, it is possible that teflon tape - or something similar - was used to install the zinc originally. The tape electrically isolates (maybe partially?) the zinc from the metal it is to protect - you are not getting full protection, thus little erosion

2. If you have a zinc holder in good shape, you need not pick out the pieces. Just place the old zinc holder in any descaler - CLR might work, as would the electrolyte from an old battery before recycling - or any acid. The result is a brand-new shiny zinc holder with no residual zinc that is ready for a screw in zinc rod. Want to be doubly sure, just place a very small quantity of "Bachmann Trains - E-Z LUBE - CONDUCTIVE CONTACT LUBE" or some similar conductive lube - available at Home Depot for aluminum/copper joints. If you use a "dielectric" grease - as most people do when they use plumber's tape or similar stuff, you are isolating the zinc from its circuit - and doing exactly the opposite of what you want. Your photograph looks like someone has protected the zinc in the past. My suggestion, remove and clean the zinc from its holder, clean it with acid - lemon juice if that is what you have, clean the holder the same way and re-install te zinc in the holder and the holder in the device to be protected using any available conductive grease - the aluminum/copper stuff from Home Depot is under $10 and works fine. Wait 1/2 your usual maintenance interval and inspect the zinc again. OR - blindly replace it and hope for the best.

The zinc is meant to sacrifice itself - if it doesn't go away, it isn't working

[Jimmyhenry]

It looks to me that your anode has not worked.
When you reinstall a new one test the brass end to the engine with a circuit tester to make sure you have contact.

[garyfrankovich]

DO NOT EVER WIRE BRUSH A ZINC TO CLEAN IT! The second you use a wire brush on it, very small pieced of the wire bristles will break off and lodge in the zinc, INSTANT BATTERY when you add the salt water, the zinc will dissolve so fast it will make you head spin. If the zinc is coated with a white oxide (from being in fresh water) or has some marine growth on it, you can try cleaning with a stiff plastic bristle brush.

[Nicholson58]

I have seen too many that looked OK but turned into a sh- mess soon after. They cost pennies. Toss them.