Stephen,
One option is, you can get a hydrofluoric acid (several brands to choose from) to etch the tile. This will increase the slip resistance. However, it will also open the surface which allows to tile to attract and hold soil more than normal.
Another option is to use a maintenance product called Friction. It is diluted and mopped on. It works very well and can increase the slip coefficient dramatically. However, it gets walked and worn off so reapplication must be routinely for high traffic and periodically for low traffic.
Outside, I would think every 7-10 days. Good things are that it is easy to apply, mop or even a sprayer, it is rated by UL and NFSI (National Floor Safety Institute).
There may be other options too, these are two immediate solutions.
Good luck,
Bob

Sent from Bob Murrell's iPhone
M3 Technologies, Inc.
865-607-0957
Office 800-342-4533
www.go2m3.com

> On Apr 13, 2018, at 1:20 PM, Stephen Webb <stephen@newlifemarblerestoration.com> wrote:
>
> Greetings partners, Client has a 40myr old ceramic (8") tile exterior halls (condo) well maintained  that new owners want to have a non slip finish applied. Is there anything appropriate that you can recommend?
>
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