Suitable for:
Carbon steel, stainless steel, alloys with chrome or P91/92
Removes:
Iron oxides (rust) and light oil, grease and atmospheric contamination.
Cleaning with EDTA (Demclean 94®) is carried out in a pH neutral environment. In addition to iron oxides, this method also removes light oil, grease and atmospheric contamination. The rust (iron oxide) is dissolved and a strong iron-EDTA complex is formed. This makes it possible to increase the pH after cleaning without the iron precipitating as iron hydroxide. After this neutralization, the steel is passivated by dosing sodium nitrite.
Pickling and passivating is carried out with 1 liquid (passivation liquid usually with nitrite), so less waste water is released. The waste water that is released during this cleaning can be treated by means of biological water treatment, adjusted for EDTA processing.
Advantages
- pH neutral cleaning liquid;
- Passivation with the cleaning liquid;
- Not corrosive to other metals;
- Shorter cleaning time;
- Smaller amounts of waste water;
- Suitable for higher alloyed steels that include chromium or P91/P92;
- Can be used if both carbon steel and stainless steel material are present;
- No use of corrosive chemicals during the pickling step;
- If used incorrectly, there is a smaller chance of corrosion of the base material;
- Only suitable method if there is a risk of crack corrosion (for example due to certain welding methods).
Disadvantages
- Does not remove welding skin, mill scale, annealing skin & silicate compounds;
- Can dissolve less iron oxides;
- Cannot be used if copper piping is present;
- Cannot be used to dissolve present copper oxides;
- Waste water processing is relatively expensive.