Welding Tips and Tricks

Is there any negatives to welding 304 to 316?

Here is my guess:

It is generally stated by mfgs that 316 has higher corrosion resistance than 304 due to the added molybdenum, so you might reduce that property in the weld area depending on what it is exposed to.

That being said I have heard from people that more important is having an excellent surface finish. You can save money on 304 and polish really well and achieve the same results or better than 316 in marine environments. The pitting you hear about occurs due to areas in the surface finish that are not as smooth. Grain pattern matters.

If it we me I'd welding it up with 316L and I bet it would be just fine.

This is a pretty good read on stainless if you are generally interested: https://www.unifiedalloys.com/blog/stai ... -families/

Thanks for the info

as far as welding 304 to 316 goes afaik theres is no issues. very commonly done, a lot of tube fittings are 316 and are welded to 304 tube.

Stainless 316 contains more nickel than stainless 304, while 304 contains more chromium than 316. Stainless 304 usually consists of 18% chromium and 8% nickel. Stainless 316 is made up of 16% chromium, 10% nickel and 2% molybdenum.

Never heard of getting better corrosion resistance with 304 than 316 in saltwater -- the chlorides in various salts are tough on SS -- but yeah, a smooth / polished finish is important in either case, due to crevice corrosion. I've heard of guys "cleaning up" SS in saltwater with a wire wheel, which is about the worst thing one could do...

Also, from a corrosion standpoint, it's important to get in and get out as fast as possible when welding stainless, as the longer you have it hot, the more chance you have of getting carbide precipitation, which leads to rust/corrosion.

On my own boats (saltwater), I'll always pay the extra $ for 316 over 304.

Lightning wrote:Never heard of getting better corrosion resistance with 304 than 316 in saltwater -- the chlorides in various salts are tough on SS -- but yeah, a smooth / polished finish is important in either case, due to crevice corrosion. I've heard of guys "cleaning up" SS in saltwater with a wire wheel, which is about the worst thing one could do...

Also, from a corrosion standpoint, it's important to get in and get out as fast as possible when welding stainless, as the longer you have it hot, the more chance you have of getting carbide precipitation, which leads to rust/corrosion.

On my own boats (saltwater), I'll always pay the extra $ for 316 over 304.

I don't know that 304 would be better, used to work at a shop fabricating sst pipe for reverse osmosis systems, always 316L or better (duplex, super stainless even a few Ti systems)

After fabrication passivation was a must.

Also saltwater is very different from one location to another, ie. Gulf of Mexico or Bahamas etc.