any metallurgists out there?, page-6

Hi Hanrahan,


"I've bought new marine grade bolts but my son says that SS corrodes if there is no O2 to form an oxide coating."

I have two 1 inch propeller shafts that have been in salt water for 23 years with no problems.

I have zinc anodes bolted on shaft with S/S bolts.Sacrificial Anodes corrode away as they should, but bolts are fine.

S/Steel and dissimilar metals create electrolysis.

A yellow paste called "Duralac" is great to stop electrolysis.

There is 316 marine grade, BUT, most most bolts are made from 304S/S , because it's stronger I am told.

How about giving galvanized bolts a go.

The guys who run the stinger nets off the beach, rap a sort of greased/ fish oil/rust proof lagging around some of their equipment.

These guys have their workshop near to me, so if you still have problems, let me know exactly what you are using, types of metal and fresh or salt water.

These guys were very helpful to me in what to put on my new mooring. I will ask their advice for you. They have many years of experience on a large scale with underwater equipment.

cheers,
sypaladin