Anode is made for Bukh
, with composition:
# Cadmium: 0.025%-0.07%
# Copper: 0.005%max
# Iron: 0.005%max
# Lead: 0.006%max
# Aluminium: 0.1%-0.5%
# Zinc**: Remainder
So mostly Zinc and not appropriate, as DeepFrz suggested (thanks).
According to Martyr (anode manufacturer):
ZINC - For use in salt water
ALUMINUM - For use in salt
and brackish water
MAGNESIUM - For use in fresh water
The anode's apparently not needed for the fresh water cooled engine, since the Bukh
manual only mentions the need for 25% ethylene glycol in the coolant to inhibit corrosion
. The heat exchanger
has its own anode. I'll remove the zinc anode from the block.
So the crud that deposited on it is most likely a chemical reaction between something in the coolant and the zinc anode. Don't know what chemical reaction, but it seems it should not be unexpected. May take a chemistry post-graduate to explain that reaction.