Stainless steel

I would avoid stainless Steel, if you do go with it, it should be a 316SS/316LSS at the minimum. Certain chemicals added can increase the corrosive propery of seawater. I have seen 316SS and Monel screens disappear very qucikly. Many companies are getting away from Stainless for any seawater application.

 

Thanks for the input! The weld ing would have been by TIG (tungsten with inert gas) using again surgical steel welding rods.

Would aluminium be any better? i was planning on using a sealant such as G4 (dont know if you guys get that over there!) which is a paint used for sealing cement or wood to water tight it .

 

this gives a little info, good forum for eng. questions-

http://www.eng-tips.com/viewthread.cfm?qid=44009

 

[quote author=geologeek link=board=General;num=1103505268;start=0#11 date=12/20/04 at 10:08:05]Would aluminium be any better?[/quote]

Nope. Almost certainly worse. Aluminum (aluminium) corodes very quickly in salt water, and the resultant compound is a powdery oxide with almost no structural value.

 

I would go with PVC. We build strainers and are getting way from using any stainless for seawater. We are even starting a PVC strainer and filter line.

 

[quote author=Malachi link=board=General;num=1103505268;start=0#14 date=12/20/04 at 12:30:14]I would go with PVC.  We build strainers and are getting way from using any stainless for seawater.  We are even starting a PVC strainer and filter line. [/quote]

He's already said that stainless is by far the cheapest route for him. (Becuase of his fathers trade, I'd assume.) We've pointed out the plastics are a better long term solution, but that doesn't make Stainless a bad idea. If he uses a reletively heavy gage, a little rust isn't going to be a problem at all. If I had kin that could tig weld stainless for reletively little money, I'd jump all over it! (...and have lots of non-aquarium project in line, too!)

 

I am just issuing a word of caution. I deal with stainless steel and seawater from around the world and I can see how relentless it can be. And I would not want any rust to affect anyone’s system. I would attach some photos of a seawater (Indonesia) application after one month (pic was put on an excel spread sheet). It was 316L Stainless Steel Screen which was passivated. It is already showing signs of rust and pitting I was actually supposed to fly to the jobsite last week but my trip got snowed out. Another problem with stainless is that it can be easily contaminated. If a brush was used to prep a weld with a few carbon steel flakes this will containment the weld and rust will attack this area. I am not saying you can not us stainless but just be careful. I would keep a passivation (pickling) paste handy incase of emergency, also make sure it is safe for potable water.

Also I wish stainless steel was cheap in the states, the price is ridicules right now and still rising. It will probably still keep rising until we are out of Iraq.

 

Well, since we don't have as many steel plants anymore, I don't see the price coming down any time soon! :-/

 

What about the conductivity properties of steel, with salt water in it? Any concerns there with electricity etc...? I don't know, just a thought...

 

I'd personally learn how to deal with Acrylic or pay someone to do it for you. Saltwater will eventually degrade any steel and corrode AL. It's just a matter of time. I wouldn't trust it. If steel starts to rust it will free up iron into your water. Algae LOVES iron. Instant algae bloom. Be careful.