In-line CO2 diffuser corrosion, supposed to be directional?

[Disaronno]

Hey all. I decided to clean the diffuser after who knows how long it has been since it was last taken apart. The aluminum body had severe corrosion and build up of hard crust. It was mounted from filter output -> plastic body half (contains ceramic) -> aluminum body -> tank output.

Was it supposed to mounted reverse so the plastic is on the output side? Or is this unavoidable with the chosen metal?

 

[ExcitableBoy]

If the Aluminium body had been still in contact with water it wouldn't have made any difference then. Anyway

But aluminum, when exposed to water and oxygen will very quickly corrode. Most can identify rusted steel from its familiar orange color. Aluminum corrosion actually looks white.

The process of aluminum corrosion is known as oxidation. The resulting aluminum oxide is a thin, hard layer that actually protects the metal from further corrosion.

Aluminum oxide appears as a powdery white or dull gray coating. As oxidation occurs, it hardens and creates a protective layer over the newly exposed areas of corroded aluminum. The aluminum corrosion process is actually halted by oxidation—the metal won’t continue to deteriorate unless the aluminum oxide is removed. As mentioned earlier, unlike rust, which has a flaky, orange appearance, aluminum oxidation cannot be easily chipped off the metal surface.

link

 

[Disaronno]

Somehow I thought the anodized surface would protect it because the aluminum shower caddy is fine but apparently not 🙃

I've reinstalled the diffuser as it's not leaking and there's no replacement on hand. Guess I should look into a plastic inline or reactor this time around.

 

[Zeus.]

Well aluminium is a very reactive metal, it very quickly oxides in the atmosphere and forms a protective oxide costing which prevents/reduces futher oxidation. IMO with it being mounted the wrong way the low pH and/or the high CO2 has caused the corrosion. If it had been fitted correctly it would of been fine. Easy mistake. At least you spotted it before the leak happened.

 

[ExcitableBoy]

Well, it might look unsightly but once the surface has been oxidized the aluminium won't be corroded anymore.
Probably your shower caddy has received a better treatment and/or the "environment" is different