Efflorescence
HOW TO REMOVE FROM TILES
I assume if you have efflorescence on a ceramic tile that it is either coming up through the porous grout joints or it is an unglazed porous ceramic tile. Glazed ceramic tiles have a surface that has a fired-on glass-like impervious coating, so you normally would not have efflorescence on that surface. Although it can migrate through some porous natural stones or concrete.
Efflorescence is generally a mineral or salt crystalline compound found in the ground and within concrete. This dissolves in moisture that migrates up through the ground and concrete to the tile surface, where the moisture evaporates leaving an expansive salt residual.
Normally an acid based cleaner will remove the efflorescence, but you have to be careful that the acidic solution doesn’t damage the tile or grout. A properly mixed diluted vinegar can be used if applied correctly.
Sulfamic acid is the safest acid to use. Don’t use muriatic acid as it is too corrosive. Manufactures of cleaners and sealers sell diluted phosphoric acid cleaners for this purpose.
REMOVAL
A De-Calcification treatment can remove efflorescence (the visible salty crusts) and help to prevent recurrence, but it cannot solve the problem and it is likely to recur at some stage.
Prevention is far better – only used premixed grout (never unwashed sand) and isolate the source of salts (substrate) from the tiles by quality waterproofing agents.
In heavy and recurring situations, efflorescence removal from the surface is only temporary and prevention through regrouting may be required.
Of course as long as the source of the salt and moisture remains the efflorescence will return. I would adequately clean the tile and let it dry, apply a sealer that will help retard the efflorescence, but that has to be maintained regularly too. https://aquamix.com.au/products/problem-solvers/eff-ex-efflorescence-remover/
You can’t do much about eliminating the source of the salt, but if you stop the source of the moisture then it can’t transport the salt solution to the surface of the tile. I would look at adjacent planters that might be too wet and supplying the moisture that is migrating to the tile surface.
