Can anyone help with removing leaching from grout?, adhesive?, cement base? to my front door steps which are tiled with slate. The attached photo shows the white staining. It is hard and will not scrub or wash off.

Hello Charles and welcome..


You have what looks very much like Efflorescence.

I would recommend some Aqua mix Eff-Ex..

All the info is here..>> http://custombuildingproducts.com/do...er=diy&lang=en

or you can try Aqua Mix Phosphoric Acid

Aqua Mix Phosphoric Acid Substitute is a premixed acidic treatment designed to remove grout haze, mineral deposits, rust stains, mortar smears, and efflorescence. Effective for the removal of most hard water stains, lime deposits, and soap scum. Also removes cement grout and mortar residue from tile, concrete, and masonry. Etches concrete. No VOCs, No phosphates.

This could return though as obvioulsy you have some salt issues in the step substrate which is rising to the surface..
It can be quite common in outside situations like this but can be controlled with products like above..

Once you get them clean then we can advise something to seal them with.

Originally Posted by Charles Bean

Can anyone help with removing leaching from grout?, adhesive?, cement base? to my front door steps which are tiled with slate. The attached photo shows the white staining. It is hard and will not scrub or wash off.

I maybe wrong, but this looks like a common problem when a sealer designed for indoors has been used outside. The more frequent wetting causes these white stains.
Not sure at the moment how to remove,will try do a bit of research.
Have seen this before. Also saw this inside a house, customer had an expensive glass walkway built between her house and extension. This was tiled in black limestone & tiled. She had a persistent leak, water was seeping through for months. Same marks appeared. tiles had been sealed with sealer that was for inside & not constant, frequent wetting.

In theory, no need to seal slate tiles outside.
how often do you get someone to re-seal your slate tiled roof ....
Never,because it has never been sealed !!!

NIck you can actually see the salt formation.. it deffo isn't sealer blooming.

I have the same issue on an upper deck. White looking stuff dripping down the back of my house. I want to replace tiles but wasn't sure if this will keep continuing. I hate repairing, painting every four months. Any ideas.