CitriSurf®
Passivating stainless steel with citric acid
CitriSurf® is a citric-acid-based cleaning and passivating solution for industrial applications. It safely and environmentally responsibly removes free iron from the surface of stainless steels and creates important conditions for corrosion-resistant, reproducible stainless steel surfaces.
The short path to the right solution
Physical property
| Specific gravity | 1.2 |
Density | Concentrate: 1.216–1.226 |
| State | Liquid* |
| Chemical composition | Citric acid, water and cleaning and passivation additives |
| Working temperature | 45° C to 60° C |
| Flash point | Non-flammable |
| Water solubility | 100% |
| Normal working concentration | 10%–20% of the initial solution |
| pH value of the initial solution | 3.0–3.2 |
| pH value of the working solution | 3.0–4.5 |
| Packaging units | 20-litre plastic canister |
*For automated processes, the foam-reduced version CitriSurf®3250 should be used
**For products where biocides must be avoided, please ask about CitriSurf 2250BF
The cleaning components of CitriSurf®2250 intensively remove all oil and grease residues from the surface. The special citric acid then removes the free iron ions from the upper molecular layers. This produces a positive change in the chromium-to-iron ratio, resulting in improved rust resistance or passivation of the surface. No impairment of the function of the passivated part is to be expected. Weld seams and solder joints are also not attacked, but are freed from contamination with free iron. Other materials, such as aluminium, can also be treated with CitriSurf® to remove iron components and iron-containing contamination introduced into the surface during machining. The stated concentrations and times refer to use on stainless steels. For other materials, special parameters must be developed through testing and/or in consultation with the developer or manufacturer of CitriSurf®.
Although the use of CitriSurf® is generally very safe, citric acid can cause skin irritation. Please refer to the safety data sheet for further information. During heating of the solution, cloudiness may occur. This disappears again after the heat source is switched off and is harmless for the function and the treated products.
CitriSurf® is not classified as dangerous goods and can be disposed of without difficulty in its delivered condition. However, during use, components may enter the solution that require special disposal. The relevant laws and statutory regulations for the disposal of liquids and chemicals must be observed. Please consult the responsible local authorities.
CitriSurf®2250 should be stored between 10° C and 70° C in stainless-steel or suitable plastic containers. If the solution freezes, it can be used normally again after thawing. During prolonged storage, the solution may crystallize; this effect is harmless and not damaging, and the crystalline components dissolve again when heated.
For further information on maintaining the finished passivation solution, please refer to the corresponding maintenance instructions.
CitriSurf®2250
Stainless-steel passivation: CitriSurf®2250 is a high-quality product for cost-effective and efficient cleaning and passivation of stainless steel. It removes free iron from the surface of stainless steels and complies with the procedures for stainless-steel passivation described and required in the ASTM A-967 & AMS 2700 standards.
Particularly suitable for martensitic steels and stainless-steel grades with a low chromium content.
APPLICATION
- To achieve the best possible result and extend the service life of the solution, the parts to be treated should be pre-cleaned with a highly alkaline cleaner before CitriSurf® is used. The highly alkaline cleaner KleerKleen 4002 is very well suited for use with CitriSurf®. The passivation system, including tank and pumps, should be clean and dry before the solution is prepared. Although CitriSurf® itself is an excellent cleaner for many cleaning and passivation processes, coarse oil and grease contamination should be removed beforehand, as it can otherwise impair effectiveness.
- CitriSurf®2250 is supplied at an initial concentration of approx. 50% and should be prepared with distilled water:
- 5% solution: dilute 1 part CitriSurf®2250 with 9 parts water.
- 10% solution: dilute 1 part CitriSurf®2250 with 4 parts water.
The required concentration depends on the materials to be passivated. - The parts to be passivated should remain fully immersed in the solution until the free iron on the surface has been completely removed. The average exposure time is 10 to 30 minutes, but can be further optimized by test series using your own products. Then rinse the product with clear water and dry immediately in air. Drying time can be shortened in a heat oven, but should last at least 60 minutes. CitriSurf®2250 is an oil-separating cleaner. If oil residues have to be removed from the cleaning container, this should be done before the next use. Yellowish discoloration of the solution is normal and is caused by the dissolved iron content.
Consulting & Contact
For many years, we have supported companies with stainless steel passivation, from root cause analysis through to implementation, including on site by arrangement.
How can CitriSurf® be ordered?
Exclusively from MKK GmbH, Oldenburg
Order by email: order@citrisurf.de
Please note:
- Provide your VAT ID
- Billing address and delivery address required
- Orders before 12:00 noon: usually shipped on the next working day
- Delivery date = shipping date (transit times depend on the logistics provider)