Hi Ilona,

the problem is not the stainless steel but the aluminum-zinc.

Zinc is bactericidal but not as good as silver.

So I think the following scenario to be likely:

You deactivate the silver particles by some unknown process most likely a tight layer of titania.

(Do you bake the sol-gel to complete water loss?)

You generate cracks to the substrate so that these are available to the water that carries the bacteria.

This water will attack the zinc but not much the surface of SS as this being protected by chromium-oxide.

Look with a high resolution optical microscope if cracks are existing - if not visible, then proceed to a SEM, or start with a sensitive chemical analysis.

From the coatings we made (vacuum sputtering no sol-gel) we experienced pin-holes in any coating and cracks in some.

Have success!

RHABE

Hi RHABE!

Thank you for your answer.

We are a producing company (make metal doors and frames) and do not have laboratory equipment.

We would like to coat our doors, handles, frames with titania sol gel that also contains silver (for use in hospitals).

We buy our sol gel from Kina.

Sol gel is sprayed on testpieces and dry in room temperature (20 grades Celsius). Coating is dry after 20 minutes.

Do you have a suggestion for antibacterial coating on our stainless steel products?

With best regards

Ilona

Hi Ilona,

By anatase do you mean Titanium Dioxide (TiO2)?

Spencer.

Hi Scapolie!

Yes our sol gel has 0,85w% Titanium Dioxide (=Titania) in it. Titanias chrystal form is anatase (particle size 10 nm). The sol gel also has silver ions in it (Ag+). Titania has a photocatalytic activity in 385 nm and silver destroys bacteria also without light.

Ilona

Hi Ilona,

Yes I can see where you are comming from, but Anatase and Brookite happen to be a very unstable Titanium dioxide minerals, why not try the stable form "Rutile"?

Spencer.

Hi Scapolie!

The photocatalytic activity is best with anatase Titania.

Ilona

It's easy to have differences in bacteria count log/lag phase from sample to sample, or even species-specific effects, without an understanding of what's going on. Let me know if you want to discuss further off-line. I have some knowledge of both anatase and bacteria measurement techniques.