SS tank

[maytag]

I am currently looking at a hydraulic upgrade for a local industry, part of which involves construction of a new tank. The tank is to be constructed from 304 SS. Even though it is more time cosuming I would like to weld both outside and the inside of the tank. How much will the MIG welding process reduce the corrosion resistance on the inside?
Thanks,
Maytag

 

[Metalmeister]

Probably not all all; but what does the tank hold? The corrosion resistance is more affected by welding parameters than welding process.

 

[maytag]

This tank will hold hydraulic fluid-mineral based.
Higher end systems generally will have SS to avoid the rust and corrosion issue. Welding both inside and outside insures that we are not plagued with a pinhole leak.
Thanks,
Maytag

 

[unclesyd]

What type tank are you considering is it atmospheric or hold slight pressure?
What is the thickness of the SS?

This information may help determine the welding process. Most SS tanks will have full penetration welds to prevent crevice corrosion.

 

[maytag]

The tank is open to atmosphere-hydraulic oil will be approx 44 inch deep-I believe this will generate less than
1 1/2 psig at the bottom. Material is 304 SS plate, 3/8 inch thick. On other assemblies I have used the MIG process,
using Shield Bright wire( has flux in it) and also shielding with CO2 gas.

Maytag

 

[unclesyd]

I definately would weld the inside using your process based on the plate thickness. It would not be very much additional work to make it a full penetration weld.

 

[strider6]

MIG welding is used in welding SS materials and if the welding is done correctly, choice of shielding gas for example, it will no imply any consequence on corrosion properties of the material.
I think you need to change the shielding gas. The gas mixture changes with the metal trasfer type:spray-arc, short-circuiting, or pulsed-arc transfer.
Usually mixture of Ar + 2%O2 or 90% He, 7-1/2% A, 2-1/2% CO2 are used 'casue the CO2% can have an effect on Corrosion properties: "keeping the CO2 level low enough so that it does not influence the corrosion resistance of the metal." (ref

http://www.lincolnelectric.com/knowledge/articles/content/migweldss.asp)

As someone else said the problem is the corrosion roterties of the metal in contact with the fluid. Are u sure that no chloride are contained in the mineral oil?

Welding Stainless Steel

S.


Corrosion Prevention & Corrosion Control

 

[maytag]

strider 6,
thanks for your reply. The Shieldbright is an Esab wire I believe and Esab recommends either an Ar.75 %-25 % C02 mix or 100% C02. I have had good luck following their recommendations in the past but this was not tank fabrication. I could not tell you for sure about the chloride-the 304 SS is common for hydraulic tanks in the industry I serve.
Maytag