304 vs 316 ss for railings and fittings

clayhubler

I am going to make a cargo roof rack and radar mount for hammerhead. I have lots of 304 ss tubing and fittings that I was planning to use, but after doing a quick test and dunking in salt water the tubing and fitting got small amounts of surface rust after only one day. I was surprised by this, because I see that lots of marine deck cleats and various fittings are offered in 304ss. The rust is just on the surface, and came off easily with just a scotch brite pad.

Is there a way to polish/ wax the railings so they do not rust, or do I need to use 316 material? Thanks!

tsturm · Posted: Wed Apr 28, 2021 5:28 pm Post subject:

I use 316 & no issues 304 if mirror polished is ok but will not last as long. Thumbs Up

T.R. Bauer · Posted: Wed Apr 28, 2021 9:41 pm Post subject:

I've have had what you describe happen to me before because I used steel tools to make the bend. Or because it simply put the stainless part in the vice to hold it while I welded on it. Cleaning it up really made a difference in my case. But, I have since switched to making everything out of 5052 aluminum since it is easier for me to work with and doesn't really corrode at all.

tsturm · Posted: Wed Apr 28, 2021 11:00 pm Post subject:

T.R. Bauer · Posted: Wed Apr 28, 2021 11:22 pm Post subject:

clayhubler · Posted: Thu Apr 29, 2021 10:04 pm Post subject:

Alu is much easier to work... I've never welded 5086. How does it compare to 6061? If I remember right 5086 will bend okay too.

Barry Rietz · Posted: Thu Apr 29, 2021 10:36 pm Post subject: Aluminum & Stainless

Clay, 316-L stainless is the best choice for marine applications. The "L" stands for low carbon and is difficult to locate. If you can find low hydrogen filler wire when TIG welding the railings, it will be porous free and buff up to match the base metal. Then, if you really want to prevent rust and dulling of the finished weldment prior to installation, have it "passivated" at a plating shop. If you decide to use aluminum, look for tubing that has not been tempered. It is more ductile and will yield to the bending without cracking not to mention easier to weld. Post a photo of your work when completed.

T.R. Bauer · Posted: Thu Apr 29, 2021 10:53 pm Post subject:

clayhubler · Posted: Fri Apr 30, 2021 12:46 am Post subject:

Thanks guys, I know I'm not going to bother having it passivated so I think I'm going to try to source some 5052. I'm thinking it will probably be cheaper than the ss also. I'll post some pics when it's done. Will probably be in a couple months tho.

I've actually only made one project from aluminum, which was a hand railing. I am much more comfortable welding ss. Does alu pull and warp as badly when welding?

tsturm · Posted: Fri Apr 30, 2021 9:02 am Post subject:

T.R. Bauer · Posted: Fri Apr 30, 2021 10:28 am Post subject:

He's right about the tubing being 6061, but if all they have is 6063, it is very similar stuff. And he's right about it warping. You can control that with patience and technique with TIG. With MIG it will be a bit harder since you can't control amps dynamically, but if you only weld a couple inches at a time, let it cool, and don't cook the workpiece, it will not warp very much - if at all. I do that with TIG also when welding sheet and it comes out good. Also, it really helps to use 1/4 of 3/16 as a base instead of 1/8. But, again, I am not a pro - just a hobby for me.