Is there any advantage or disadvantages to having a rudder built out of stainless ?
One of my old mates has a stainless rudder, can't keep paint on it, barnacles love it & it burns anodes like crazy. His words not mine. He built this particularly boat 25 years ago & had built several others, so I guess he's got a comparison base
Nope - stainless is a passivating metal and likes ot have oxygen around it to make a thin oxide coating that protects the rest of the metal. Under water is not stainless steel's strong suit, hence why bronze is usually used in metal seacocks under the water. An old Australian magazine had a clever metallurgist (Ian Ward - Moth legend) write about the idea. Someone did a keel out of stainless and it was full of holes in a few years.
Select to expand quoteKankama said..
Nope - stainless is a passivating metal and likes ot have oxygen around it to make a thin oxide coating that protects the rest of the metal. Under water is not stainless steel's strong suit, hence why bronze is usually used in metal seacocks under the water. An old Australian magazine had a clever metallurgist (Ian Ward - Moth legend) write about the idea. Someone did a keel out of stainless and it was full of holes in a few years.
Thanks for that , I had my doubts about it, just been looking a yacht and luckily it was out of the water was surprised to find it had a stainless rudder.
Select to expand quotecammd said..
Mine has a stainless rudder post, skeg and keel made from 2205 duplex.
Sounds like that would work but how do you know they used 2205?
2205 is a (two phase) ferritic/austenitic stainless steel with high strength and excellent corrosion resistance, as supplied in the annealed condition with a maximum brinell hardness of 290 (Rc31).Characterised by high yield strength, double that of the standard austenitic stainless steel grades, good fatigue strength plus excellent resistance to stress corrosion cracking, crevice, pitting, erosion and general corrosion in severe environments. Again generally out performing the standard austenitic stainless steel grades. 2205 cannot be hardened by thermal treatment, but strength and hardness can be increased substantially by cold working, with subsequent reduction in ductility.It is used extensively by the Marine, Chemical, Petrochemical, Pulp and Paper, Oil and Gas, Transport and allied processing industries.Typical uses are: Anchor Guides, Conveyors, Fasteners, Bushings, High Strength Pump Shafts, Propellor Shafts, plus various applications currently using standard austenitic stainless steel grades.Material Magnetic due to its part ferritic structure.
Select to expand quoteMAGNESIUM said..cammd said..
Mine has a stainless rudder post, skeg and keel made from 2205 duplex.
Sounds like that would work but how do you know they used 2205?
The gentleman I bought it off told me he used 2205 for the keel and skeg. Also the designers website confirms it.
Learn something everyday, my rudder shaft is stainless but I do check it regularly for pit corrosion.
