Stainless Steel Welded Components in Contact with Water: Mold or Oxide?

Posted on

One of our readers asked an interesting question. About a month and a half after installing a pool ladder made of stainless steel, the area where the welds are located and submerged in water developed some issues. What should you do if mold or oxide forms on welded stainless steel components?

The dilemma: is it mold or oxide?

Before taking any action, it was necessary to determine whether it was mold or oxide. Depending on the specific case, the treatments for the stainless steel component will differ. If it is mold, for example, the ladder needs to be removed and treated with anti-mold products suitable for stainless steel. It is necessary to ensure that the chloride concentration in these substances does not exceed 300 ppm and that they do not contain highly aggressive acids (e.g., bleach, muriatic acid, etc.). Additionally, high summer temperatures do not help to slow down this phenomenon!


Welded stainless steel components. What to do if it is oxide?

If it is oxide, the problem is more serious and probably cannot be resolved definitively. If the plates to which the supports are bolted are not stainless steel but metal, the junction will obviously oxidize. Between materials with different potentials, a galvanic current is created, with chloride-rich water acting as an electrolyte. Electrons from the metal with the lower potential will migrate to the one with the higher potential. Therefore, we recommend avoiding this type of connection, especially if the metals involved are immersed in the same liquid. What should be done, then? The only solution is to replace the plates with ones made of the same stainless steel as the supports. Crucial, in the case of immersion in pool water, is the choice of the type of stainless steel. Even AISI 316 may not be sufficient.


But why does oxide form on welds?

Stainless steel welds are extremely delicate. They must be done with great care, paying attention to various factors that can influence resistance to oxidation. If the stainless steel used does not have a very low carbon percentage (below 0.030%), during welding (and the consequent increase in temperature), chromium carbides can precipitate. The compound thus does not passivate. To temporarily remove the oxide, a pickling agent can be used, followed by a passivating agent to recreate the passivated layer (e.g., products like Sparcle from Cheamsearch). But to definitively resolve the problem, it is necessary to eliminate the cause that triggers the onset of corrosion as mentioned in the previous paragraph.

Visit our website and discover how easy it is for companies to buy our stainless steel fasteners online.

Want to read more articles? Continue here.

Leave a Reply

Your email address will not be published. Required fields are marked *

Informativa Privacy Ai sensi dell’art.13 del regolamento (UE) 2016/679 i dati personali raccolti nella presente forme saranno trattati solo per rispondere alle richieste inviate. Per maggiori informazioni consultare l’informativa Privacy completa.

WordPress Theme by RichWP