Remove rust stains on stone slabs carefully


Although hard and massive natural stones are very resistant, they are usually very sensitive to the effects of acid. When removing rust stains on stone slabs, their acid compatibility must first be checked. From non-sensitive glazed surfaces to sensitive porosity, the bandwidth reaches.

Dosed acids in homeopathic quantities

Since acids are the most important and effective antagonist of corrosion when rust stains are removed, they are contained in almost all rust-removing agents. Before using, it is essential to check whether the affected stone slabs on the terrace, for example, are acid-resistant. Typical consequences of using a wrong or too aggressive agent are:

  • Loss of loss to total stunting
  • Color changes or complete loss
  • Emergence of fragility

A widespread prejudice is that natural stones, which do not scratch when scratched, are also acid-resistant. The two processes are not related and the scratch test does not say anything about the acid compatibility.

Contra-productive and discoloring effects

Some acids even trigger the opposite of the intended effect. If, for example, hydrochloric acid or hydrochloric acid cleaning agents are used, they "crack" and dissolve the ores and minerals contained in the natural rock. The iron molecules exposed in this way corrode and form rust spots. Therefore, hydrochloric acid, which mainly serves for the removal of cement veils, is increasingly dispensed with.
Acetic and citric acid often cause discoloration or discoloration, especially in light granite. Phosphoric acid is a common ingredient in so-called rust conversion agents. At too high a concentration, however, hard rocks often fade. The removal of rust stains should be done with slowly increasing dose. Hydrofluoric acid, which consists of dissolved hydrogen fluoride, should never be used.

Oxalic acid in persistent cases an option

On insensitive and glazed stone slabs, oxalic acid can be used, as in the removal of rust stains on concrete. The also very toxic acid is dripped using appropriate protective measures and covered by a vessel made of glass or ceramic. After the exposure time of about one hour, the dripping point must be rinsed with clear water. It is important to pay attention to a Kalkablöschung the wastewater.

Tips & Tricks

Avoid using rust stains on flagstones as often as possible. By slightly dissolving with sprinkled lemon juice you can "blur" the stain edges and soften contrasting looks.


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