Corrosion

[Atwerp]

I am looking for responses from engineers with expertise in corrosion.
Here is the situation. I have a steel tank buried in the ground. The tank was originally installed with paint, but the paint is probably not intact currently. The tank is partially (1/2) exposed to groundwater and ½ above the water table. The groundwater in the area of the tank has a low dissolved oxygen content because of biological activity. The biological activity was created by previous gasoline leaks in the subdurface and naturally occurring bacteria.
I am trying to figure out if corrosion will be increased by injecting oxygen into the groundwater. My thoughts are since the water is currently low in oxygen an oxygen concentration cell is present. By increasing the dissolved oxygen of the water will I be increasing, decreasing or not changing the rate of corrosion of the tank?

Thanks

 

[corrosionman]

Atwerp have you not considered the idea of a Cathodic Protection System for your tank - - sounds to me its your only option
Regards CM

 

[Atwerp]

I do not own the tanks or control what goes on with them. They are in the area of a groundwater clean up project I am working on.

Anyone have an opinion on my question?

Thanks

 

[MintJulep]

Corrosion = oxidation.

Oxygen is necessary for oxidation.

It would seem to follow that increasing the available oxygen would increase corrosion.

 

[Atwerp]

It's not that simple. If that were the case, thae tank would corrode in air faster since there is more O2 available. Corrosion cells are set up because of the lack of oxygen in the water relative to the available O2 above the water line.

 

[tygerdawg]

I think corrosionman is correct. Cathodic protection system using sacrificial anodes seem to be a simple solution. They're used in offshore oil equipment and semi-submerged Gulf Coast installations all the time. Let the corrosion happen, just let it eat up the sacrificial anodes. Replace as necessary.

TygerDawg
Blue Technik LLC
Advanced Robotics & Automation Engineering

http://www.bluetechnik.com

 

[Atwerp]

Corrosionman is correct for a solution, however that is not what I am looking for.

I do not own the tanks and the owner will not be adding cathodic or other protection. I am trying to find out if my activities will affect the existing rate of corrosion.

Please Read the original question. i am not trying to solve the corrosion issue!!!!!

 

[Newmanite]

You need moisture and oxygen to create corrosion,you have both, to add more of one or the other will increase the rate of oxidation.

 

[CoryPad]

Atwerp is right about partial oxygen cells - it isn't as simple as more oxygen equals more corrosion. Beyond that, I can't comment too much on this specific problem.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Atwerp]

"You need moisture and oxygen to create corrosion,you have both, to add more of one or the other will increase the rate of oxidation."

This cannot be true. If you add more water you have less dissolved oxygen, therefore we are back to the original situation I described. Keep in mind, I in essence I have unlimited supply of water. Only a small portion is in contact with the tank.

Remember low dissolved oxygen (DO) water is corrosive. The question is, if the low DO situation, is more or less corrosive than high or "normal levels" of DO?

 

[Cockroach]

By increasing the oxygen dissolved in the liquid, corrosion rate would be expected to rise. You are essentially dealing with an aerated liquid.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada