Where the
world gathers for metal finishing
Q&As since 1989


-----

Isolation of aluminum to stainless steel in pool railing

We are building a railing that is mainly stainless but has an aluminum top cap. The top cap will be powder coated and then mechanically fastened. However this is in a pool area. Is this enough isolation to keep the stainless from corroding? The railing in place now is badly corroded, however they insist on maintaining the look.

Thanks,

Liz H [last name deleted for privacy by Editor]
Stainless Fabricator - Denver, Colorado, USA
January 26, 2011

The addition of an aluminum cap is not going to increase the corrosion of the stainless steel. If anything, it would reduce the corrosion, since aluminum is anodic to stainless steel.

Toby Padfield
Automotive component & module supplier - Michigan, USA
January 31, 2011

The aluminum that is in place now has a wax paste finish and has caused massive amounts of corrosion to the stainless steel. If the stainless were stand alone I would not worry about corrosion however, the galvanic reaction from the aluminum to the stainless is what I need to prevent. I need to make sure that the powder coat finish and EPDM-type isolation tape is going to be enough to prevent repeating the conditions that stand now.

Liz H [last name deleted for privacy by Editor]
- Denver, Colorado, USA
January 31, 2011

---

Dear Liz,
It is not your Al that causes the corrosion, but the Chloride in the poolwater. For pool-applictions, you should use AISI 316 (minimum) and have the objects electropolished for optimum corrosion resistance.
Kind regards.
Marc.

Marc Quaghebeur
- Brugge, Belgium, Europe.
February 28, 2011

---

My first question is... Was the aluminum anodized?
If not a good thick (Al)oxide layer might prohibit the start of the aluminum corrosion along with inert gasket o-ring material or silicon sealant

Greg Kulis
- Milw. Wisconsin USA
March 1, 2011