Corrosion in Aluminum Pontoon Pipe 3004 grade

[goodbadgood]

Hi

I have 1 question for you guys.

We have encountered pitting corrosion in the pontoon pipes(Al 3004) of a internal floating roof of the carbon steel tank.
The steel tank was hydro tested and half of the pontoon pipes are corroded. Initial thoughts are that it occurred due to the galvanic corrosion between Al and carbon steel tank in which the tank and Al are connected through a water electrolyte which has chloride content.

Any other reason of you have encountered similar failures.

Thanks in advance

 

[Compositepro]

If you have direct electrical contact between the aluminum and steel, it seem very likely that you wil have galvanic corrosion. And all metallic structures are required to be grounded, so they are connected.

 

[goodbadgood]

anyone has any idea about the etchant which i can use to etch the strcutre of Al 3004

 

[CoryPad]

2% hydrofluoric acid in water or 1-5% NaOH in water or Keller's.