Carbon steel, stainless steel, alloys with chrome or P91/92
Iron oxides (rust), welding skin, mill scale, annealing skin & silicate compounds.
Copper oxides can be removed by adjusting the cleaning method for decoppering (only during post-commissioning cleaning).
Cleaning with an inhibited hydrofluoric acid solution is generally applied to systems that consist of higher-alloyed steels that include chromium as an alloying element (such as P91/92 material) or are contaminated with both iron oxides and silicate compounds.
Hydrofluoric acid also has major advantages for waste water treatment. Since the pickling liquid is not drained, but displaced with water, a passivation without citric acid is sufficient.
Compared to any other pre-commission cleaning, the wastewater treatment of HF containing wastewater is very easy. The addition of calcium hydroxide (Ca(OH)2), or lime, causes the fluoride to precipitate as insoluble calcium fluoride, and iron to precipitate as iron hydroxide, which can easily be carried out on site.
- Removes iron oxides (rust), welding skin, mill scale and annealing skin as well as silicate compounds;
- Lower operating temperature (50-70°C);
- Suitable for higher alloyed steels that include chromium or P91/P92;
- Can dissolve copper oxides if present (through an adjusted cleaning procedure);
- Can be used if both carbon steel and stainless steel are present;
- Simpler waste water treatment.
- Large amounts of waste water;
- Use of both corrosive and toxic chemicals;
- Cannot be used if copper piping is present;
- Longer cleaning time;
- Greater health and safety risks with improper use;
- With incorrect use, there is a risk of corrosion of the base material.