Originally Posted by David M
The reason this has occurred is the lack of oxygen to the stainless steel
. I know it sounds counter-intuitive, but stainless steel
needs oxygen to help prevent it from going active.
One solution would be to get a drippless shaft seal
with a nipple that allows pressurized sea water
from the engines cooling
system to be injected into the area between the cutlass bearing and the shaft seal.
I realize this is the last thing you want to hear because of the cost but it is something you could add in the future when replacing your corroded propeller shaft.
My buddy owns a shafting shop and has noticed a HUGE increase in shaft log area corrosion
of both pitting and crevice corrosion
. It is due to the water trapped up in there becoming oxygen deprived. Allowing the seal to drip, with traditional packing glands, allows the water to stay better oxygenated. A PSS with the vent line will keep the water in the log at the same oxygen content as the rest of the ocean, or darn close and thus drastically minimize this issue. A direct plumbed PSS will add oxygen with the motor
running but depending upon the plumbing
may seal it off with the motor
shut down. With the advent of Gore type packings, miracle clays, Syntef lubes and folks thinking "drips less" means dripless there will continue to be a growing problem with stainless, aqualoy & nitronic shafting suffering crevice corrosion. Shafts need air and a vented PSS or a dripping stuffing box can provide this. Cut of the flow and the supply of oxygen and you run a risk of destroing your shaft.
I would not trust that shaft. Saving it, to save money
, may be an expensive mistake. $550.00 is a good deal but I would go for Aqualoy 22 especially given your vessels propensity to starve the water of oxygen.