Bimini/Rail SS 316 or 304 or what?

[roverhi]

With a strong magnet 304 is somewhat magnetic, not nearly as attracted as plain steel but you'll definitely know there is some attraction. 316 will be slightly magnetic. You can feel the attraction but barely. Don't know about 316L.

[Stumble]

The problem with the magnet test is it doesn't really tell you much other than that's it's either steel or aluminium. Work hardened 316L can be magnetic, annealed 304 won't be, or just barely magnetic.

304 and 316 really needs to be passivated before being used in the marine world, but much of it isn't. If you drop it in a citric acid bath for a few days however it will be. This removes the surface iron and leaves a layer of chromium right at the surface that reduces surface rusting no matter the grade. It's a bit of a pain but not that hard.

To passivated tubing build a PVC container and just slot the stainless in, then fill with the acid bath. If you want to be industrious agitate every few hours for two days.

[jewt]

Contact Bock Marine in Oriental NC. I got my last 2 20' sections of 316 there for $90.00 each last year. I have replaced my wire lifelines on my '69 Morgan 41 K/CB with 1 inch 316 ss several years ago and it really improves your confidence when offshore.

jewt

S/V Bifrost

[yachtgemini]

I have had electro polished (passivated) 304ss since the 1990s and crossed many an ocean and spent lots of time in Asia and the Carib. Apart from a once a year quick polish the metal continues to look very good and does not stain in any way. I have 316ss from the same era that was not polished as well nor passivated and I get a few smudges of stain.

I suspect that it is well worth your while to ensure the polishing and treatment is up to standard including extreme care in polishing out any welds than sweating over 304 versus 316.

However the same can not be applied to fasteners. 304 bolts are a nightmare for corrosion.

Hope that helps your thinking.

Ross

[AMFE]

Sounds a bit like witchcraft stumble but I will look into it appreciate everyone's help here. I think I'll call taco Marine and see where I can get it close by. seems they have a very good reputation with their stainless tubing.

[robert sailor]

Originally Posted by Cheechako

As others have mentioned and myself... regardless of 316 or 304, it's important about surface treatment, passivation, polishing etc to a large extent. Screws are rough cut, never passivated, work hardened and may have been in contact with steel. This is why they may rust quickly. Both alloys have a large percentage of iron in them. If SS is work hardened, it corrodes faster and actually may become magnetic like steel, which in the solution treated and passivated condition it will not be. A SS flat bar which had a final cold pass when rolled will be magnetic. That doesn't mean it's bad material, but it's in a different state than it should be for some uses. It will also be much stronger than soft SS. Just because your 304 is rusting, doesn't mean it couldn't be made to be much less rust prone.

Screws may be rough cut but that doesn't explain why the old ones from original construction remain rust free and all the 304 new ones are rust magnets.

[psk125]

When we needed to redo our stanchions we went to a local scrapyard. They had piles of 316 stainless tubing from a hospital that was redoing a wing and had ripped it all out. (piping for Oxygen) Much of it still had the 316 inked on it from the mill. We got it for pennies. Also found SS bimini arches and radar guards sold by the pound. Well worth the trip.

[jewt]

You can fit a 7/16" inside the 1" pipe to greatly increase its strength

jewt.

[zstine]

As for source, check if there are any marine consignment/used marine sales places... or even marina's that do a lot of their own work. I bought a 4 bow bimini frame (1" 304 i think) for $250 in Mystic CT. It was off a 10 foot beam boat and got about 75ft of tube, plus hinges, deck fittings, etc. I was able to reuse the bends and cut and weld the straight sections to make both an arch for solar panels and a 2 bow bimini frame. You may be able to reuse pushpits, pullpits, etc. to make what you need.

[geoleo]

Originally Posted by AMFE

Thanks guys,

Is there a way to test stainless to determine weather it is 304 or 316?

MAGNET

[geoleo]

Originally Posted by AMFE

Sounds a bit like witchcraft stumble but I will look into it appreciate everyone's help here. I think I'll call taco Marine and see where I can get it close by. seems they have a very good reputation with their stainless tubing.

USe 316 fittings with 304 tube

[MarkusK]

Originally Posted by robert sailor

Screws may be rough cut but that doesn't explain why the old ones from original construction remain rust free and all the 304 new ones are rust magnets.

Original were likely installed with SS screw drivers. An old tin banger (sheet metal contractor) once told me that if you don't want SS ductwork or fittings to rust, then you must use SS tools.

[Stumble]

Originally Posted by AMFE

Sounds a bit like witchcraft stumble but I will look into it appreciate everyone's help here. I think I'll call taco Marine and see where I can get it close by. seems they have a very good reputation with their stainless tubing.

Go to your local home beer brewing store, buy 1 pounds of citric acid. Combine with 4 pounds of water. Soak stainless bits in it for a few hours.

Poof. The stainless is now passivated.

The actual recommendation is 15-20% citric acid by weight, at 150F for 4 hours. In our case we are using time instead of heat.

[sailing_gal]

I had the lifelines on my boat replaced with 1" SS tubing from the gate aft. Made by Kato. If you call them (Kato Marine in Annapolis, MD- check out their website), they will make them for you. They may have your boat measurements on hand, or will ask you to measure. Their price may be worth it since they get the steel discounted. By the way, I am quite happy with it.

Initially, it kind of made me feel like I was sitting in a cage in my cockpit, but sailing, it is a great sense of security, especially in lousy weather.

[Sailing4Jesus]

When purchasing any product, no matter it is SS TUBING or a Lawn Mower, you can never trust Salesmen. Salesmen are first cousins to Lawyers, both are born liars. When you purchase any product be sure to get a binding written guarantee. Would you buy Gold Bullion only because it looked like Gold? I think not. In the retail world, it is sad but true that no one can be trusted. Get it in writing in the form of a legal contract. Or buy several boxes of tissue to dry your tears later. As far as The Marine Environment is concerned I personally would never go with 304 Stainless. I'm A Navy Senior Chief Purchasing Officer Retired and can give witness that The United States Navy always purchases nothing inferior to 316 SS STEEL.