z Frequently Asked Questions

What is Passivation?

How do I know which CitriSurf product to use?
Please contact us for assistance in selecting a CitriSurf product that is best for your application. Primary considerations are the grades of stainless steel being used and the size of the parts.

How do I know if my parts are passivated?
The appearance of the parts is not typically changed by passivation. Accepted passivation test methods are given in ASTM A967 and other industry standards. The copper sulfate test is the most common quick and easy method for grades with high chromium content. Copper Sulfate test kits are available from Stellar Solutions.

Do I need to pre-clean my parts?
It is generally not necessary if there is only light oils or dirt on the parts. CitriSurf products are excellent cleaners and can handle light grease and oils. However, KleerKleen 4000 can be used as a precleaner if needed. Also, stainless steel alloys high in sulfur or carbon usually require a pretreatment in an alkaline bath such as KleerKleen 4002. It is best to discuss this with us.

Should I heat my CitriSurf bath?
The passivation process requires less time at higher temperatures, so we recommend heating when available, but room temperature is usually sufficient as well.

Can I use CitriSurf product with ultrasonics?
Yes, in fact we encourage the use of ultrasonic tanks when they are available.

Do I have to use DI water with CitriSurf?
No. You may use any type of water you choose for dilution and rinsing. Certain industries have purity concerns and choose to only use DI or another type of purified water. For this reason CitriSurf is produced using DI water. However using average tap water has no negative effect on the passivation process. Using purified water for the final rinse bath can help avoid waterspotting issues.

How long does CitriSurf in a bath last?
This depends on the quantity and geometry of the parts being passivated and is difficult to predict. Use bath monitoring procedures recommended by Stellar Solutions to maintain the effectiveness of your bath.

Are CitriSurf products safe to use on food equipment and other sensitive surfaces? Do they leave a coating or residue?
CitriSurf may be used for these applications. When properly rinsed, no CitriSurf remains on the surface. The protective passive layer is formed from the metal itself.

Will CitriSurf products affect the finish of the stainless steel?
Unlike nitric acid based passivation, a properly selected CitriSurf product will not etch stainless steel and will not change the surface finish.

Can CitriSurf products be used on metals other than stainless steel?
CitriSurf may be used to remove surface iron from nearly any metal, including titanium, aluminum, hastalloy, inconel, cobalt chrome, etc. It is also works as a good brightener for copper, brass, and bronze.

Are CitriSurf products safe for rubber, plastic, and brazings?
Almost all plastics and rubbers are compatible with citric acid and CitriSurf. The metals commonly used for brazing are also compatible. Please check with the manufacturer of your material for complete information. PVC pipe is not recommended for long term use with acids such as CitriSurf.

Are there any materials CitriSurf is not compatible with?
CitriSurf will cause damage to the surfaces of concrete, carbon steel, zinc, and galvanized steel. Avoid exposure of these materials to CitriSurf and rinse immediately if there is an inadvertent spill onto these materials. CitriSurf can be used to clean carbon steel surfaces if care is taken to avoid overexposure, we recommend extra dilution and room temperature operation. PVC pipe and fittings made from copper, brass, or bronze are not recommended for long term use with CitriSurf.

Can CitriSurf products be used on laser marked parts?
Laser marks are very susceptible to corrosion if they are not passivated. One of the best properties of CitriSurf is its ability to get good corrosion resistance of laser etch marks. Adjusting the laser parameters may help also. It is best to discuss this with us.

Will CitriSurf products clean off heat scale or weld discoloration?
It varies depending on the severity of the scale/discoloration, but in general citric acid does not attack the surface enough to remove these. Our Weld Wizard line of products is better able to safely removed heat and weld discoloration from the surface of your stainless steel.

Will CitriSurf pickle and passivate?
Many people tend to conflate the two types of treatment, so here’s a clarification of the terminology: Pickling is the removal of discoloration and scale by an acid treatment, its purpose it to make the surface look more uniform. Passivation is the removal of surface iron by an acid treatment, its purpose is to help in preventing rust corrosion. Citric acid based passivation, including CitriSurf, does not pickle. It’s not strong enough to etch or eat into the metal surface. Nitric acid passivation does give a little pickling (and nitric pickling gives a little passivation), which is why a lot of people still think the two things are a single process. If someone says they want pickling and passivation, ask if they are looking for just corrosion resistance or if scale/discoloration removal is needed. They possibly only want passivation and don’t know it.

Will CitriSurf products remove rust?
CitriSurf 77 Plus, 2310, and 2325 are especially formulated for faster rust removal. We also offer a kit that provides everything needed to remove rust and protect your stainless steel.

My stainless steel item is a railing, sculpture, or otherwise too large and unwieldy for immersion in a bath. What product can I use?
CitriSurf 2210 and 77 are especially made for such applications, and can be used at your location or on site. For items that have been exposed to the environment and have started developing corrosion, CitriSurf 2310 or 77 Plus should be used.

Can outdoors on-site passivation be performed during the winter months?
The time needed for passivation is related to the temperature. Room temperature or higher is preferred, but outdoor passivation in cold seasons may be done if the exposure time is extended.

Will a higher concentration of CitriSurf yield better passivation?
Yes, but higher temperatures and longer exposure times have a greater effect on improving the passivation.

Are CitriSurf products ASTM/SAE/RoHS/NSF/etc. compliant?
Yes. Please see the Passivation Specifications page.

Do we need a ventilation system to use CitriSurf products in our plant?
No. CitriSurf releases no acid fumes. When heated, only water vapor is emitted.

How are CitriSurf products shipped? Can they ship overnight?
For most of our products, the 5 gallon containers and other small sizes ship by UPS ground unless otherwise requested. Overnight shipping can be used, though it can of course be very expensive.

Do you sell CitriSurf products at any retail stores?
Several of our ready-to-use products are available within the United States from The Rust Store.
CitriSurf products are also available from our distributors around the world. If no distributor is near you, please call Stellar Solutions at 847-854-2800.

What’s that word again? Passify? Passification?
Though “passive” and “pacify” sound similar, the word pacify comes from latin meaning “to make peace”, while the word passive comes from latin meaning “to suffer”. A metal surface that is passive is able to suffer through exposure to the environment, so to speak. We say that we passivate parts during the process of passivation in order to achieve that passive surface.