*THE HULL TRUTH is the world's largest FREE network for the discussion of Boating & Fishing. Whether you're researching a new boat, or are a seasoned Captain, you'll find The Hull Truth Boating & Fishing Message Forum contains a wealth of information from Boaters and Sportfishermen around the world.
Welcome to the updated THT!
If you are having trouble signing in, please email feedback@thehulltruth.com with your username and we will help you. We thank you for your patience as we help you access the new site!
Random Quote: Golf is for people who don't know how to fish!
I have made things from 304L, 316, and 316L stainless steel for my boat and see rust forming on the welds. Is there a specific rod and grade of stainless that will hold up to Saltwater?
316 or 316L is typical. 304 is not quite as corrosion resistant. Use "L" grade (low carbon) if you are going to weld it. Other grades are availible, but I'm not sure exactly what you need. BTW, 316 is more expensive than 304.
Sorry, I didn't read your post correctly. You're asking about rod. What do you usually use, 308,309?
I don't know off hand, but I have a few textbooks at work I could check. We do provide stainless fabrications for saltwater service, but I don't know offhand what weld material is the best.
When TIG (GTAW) welding stainless, match the alloy. For example, when welding type 316/316L, we use 316L filler rod. Keep carbon levels low (i.e. use the L on the end of the grade for filler rod when available) to keep chromium carbide formation down. Use pure argon, not hydrogen argon mix, to keep discoloration down. When welding tubing, flush it with argon to prevent oxidation / weld slag in the interior of the tube weld joint. There are a few more simple tricks to make sure you get a weld that penetrates properly, and lasts.
If you really want the weld pretty, passivate or electropolish it if possible. That ties up or removes the free iron from the surface of the joint and keeps the stainless from developing surface rust / rust stains.
No, we don't make marine products - we make industrial products for chemical plants and other industrial applications.
FWIW: I'm no expert on metalurgy, but I have had a bad experience with rusting stainless - screws holding swim platform, trim tabs etc, as well as the stainless tabs themselves (rusted right through) and some underwatter fittings - enough for an insurance claim. The insurance company's surveyor blamed it on stray AC in the water near my boat slip. He explained that alternating current will break down alloys into their basic components. In the case of stainless - iron and nickel. Once broken down, the iron began to rust. He said that over time no grade of stainless would have been able to withstand it. (btw, the insurance company paid and all fittings were replaced, plus we've since moved to the other side of the marina - and an old boat hooked up to shore power with an extension cord was removed).
When TIG (GTAW) welding stainless, match the alloy. For example, when welding type 316/316L, we use 316L filler rod. Keep carbon levels low (i.e. use the L on the end of the grade for filler rod when available) to keep chromium carbide formation down. Use pure argon, not hydrogen argon mix, to keep discoloration down. When welding tubing, flush it with argon to prevent oxidation / weld slag in the interior of the tube weld joint. There are a few more simple tricks to make sure you get a weld that penetrates properly, and lasts.
If you really want the weld pretty, passivate or electropolish it if possible. That ties up or removes the free iron from the surface of the joint and keeps the stainless from developing surface rust / rust stains.
No, we don't make marine products - we make industrial products for chemical plants and other industrial applications.
tidster, if you don't know what you are talking about don't guess at it.
Marine Grade Stainless Spec?? 
