CitriSurf Citric Acid Passivation
The CitriSurf® citric acid cleaning and passivation process is based on cutting edge technology using safe and environmentally friendly citric acid to remove the free iron from the surface of stainless steel.
Stainless steel is comprised of a mixture of metals, primarily iron, chromium, nickel and in some cases molybdenum and manganese along with other materials in small quantities. It is this unique blend that allows the special property of corrosion resistance by forming an outer protective passive oxide layer. Stainless steel surfaces can be made highly resistant to corrosion if they are properly cleaned and passivated prior to use. Even with 300 series austenitic stainless steel, once a corrosion site has started, it will only get worse, being continuous and self-catalyzing. In corrosive environments the growth of the corrosion site will accelerate rapidly! Thus, proper cleaning and passivation of surfaces prior to use is essential to achieve maximum resistance to corrosion.
CitriSurf technology has proven to be a vast improvement over the traditional nitric acid formulations. After stripping the iron from the surface, the citric acid forms a water soluble complex with the iron ions, tying them up so that they are no longer able to have a negative impact. The CitriSurf bath will not allow the iron to precipitate again like nitric acid is known to do. In addition, citric acid does not pose the health and environmental hazards that are present with nitric acid. By their very nature, CitriSurf products are non toxic, non-corrosive and biodegradable. Citric acid is the natural organic acid found in oranges and other citrus fruits. It is Generally Regarded As Safe (GRAS) and is commonly used in many foods and beverages. This means that CitriSurf is compatible with the environment and can usually be disposed into sanitary sewage systems with minimal waste treatment to meet environmental agency approvals.
Conversely, nitric acid is very corrosive by nature, represents significant personnel hazards, and threatens property as well. It is also an oxidizer which increases risk and expense. Heated, its risk is intensified. After use, expensive waste treatment is necessary prior to disposal, and can expose the user to long term liability under regulatory agencies.
CitriSurf solutions represent the state-of-the-art technology that is highly effective in stainless steel citric acid passivation. After many years of use, testing, and data collection, it is apparent that CitriSurf products produce superior results at lower overall cost, and are safer and more environmentally friendly. The old constraints of nitric acid date back many years, and are no more effective now than when initially developed at a time when the chemistry of passivation was little understood. The use of nitric acid exists today only because it was long accepted as the “way to do it” through the years, including the use of Federal Specification QQ-P-35C as the industry standard. Now that QQ-P-35C has been replaced by consensus industry standards ASTM A967 and AMS 2700, it is certainly time to switch to the safer, higher performance CitriSurf system. With current technologies available for study of the surface chemistry of stainless steel, we can see that it makes sense to choose a material that eliminates the iron from the surface more completely and helps to produce a truly passive surface by creating the best possible chromium layer.
CitriSurf solutions provide the maximum protection by providing:
- Improved removal of free iron from the surface
- Faster removal of free iron from the surface
- Low hazard chemistry
- Environmentally safe chemistry
- Lower cost
- Passivated surfaces that pass all salt spray, immersion and high humidity tests
Contact us with your questions, or to discuss your application. Product samples are available to industrial customers. We have the ability to completely set you up with a CitriSurf citric acid based system to simplify your production and reduce your costs, no matter what the size of your operation is!
We look forward to hearing from you!!
These CitriSurf products are primarily used for stainless steel citric acid passivation in manufacturing and fabrication:
- CitriSurf 2050
- CitriSurf 2250
- CitriSurf 2450
- CitriSurf 3050
- CitriSurf 3250
- CitriSurf 77
- CitriSurf 2210
- See our full product list for other applications!
CitriSurf 2050 is our most cost effective product and is most useful for 300 series austenitic grades of stainless steel. CitriSurf 3050 is a low foaming version for spraying applications or tanks with submerged air blowers.
CitriSurf 2250 uses an increased pH to insure the surface is maintained on the more sensitive 400 series ferritic and martensitic grades of stainless steel. CitriSurf 3250 is a low foaming version. CitriSurf 2450 uses a pH that is higher still for the most sensitive, extremely low chromium grades.
CitriSurf 77 and CitriSurf 2210 are products for on-site and large item jobs. The CitriSurf 77 is a liquid for easy spray application, and the CitriSurf 2210 is a thicker gel version that clings well to vertical surfaces.
Industries That Use Citrisurf
CitriSurf® can be and is used in any industry where stainless steel is found, including but not limited to:
Metalworking and Fabrication
Facilities MaintenanceFood and Beverage
Food Process Equipment
Brewery, Winery, Distillery, and
Other Beverage Process EquipmentPharmaceutical
“We will save over $250,000 per year with the CitriSurf process of passivating our stainless steel parts, and have complete control of timing and quality.”
“I am absolutely amazed at how simple and easy it is to clean and passivate my parts with the new CitriSurf system. This year I will save over $50,000 in costs, and the quality of my parts is significantly better than I was getting with the old nitric acid system.”
“We are doing things with the CitriSurf product that I didn’t think would be possible. It is so safe and easy to use, and faster than the old system.”
“At first I thought I was doing something wrong, because 100% of my parts were passing the copper sulfate test, where I was getting a lot of failures and recleaning with the old nitric acid system. We will save around $50,000 this year with the citric acid system from Stellar Solutions.”
“I couldn’t believe how happy the EPA people were when we told them we were switching from the nitric acid system to the citric acid system. I feel much better now, knowing that we have a passivation system that is safer for my employees and safer for the environment.”
“Once I explained all of the advantages of the CitriSurf product to my customers and showed them the test data, they were happy to approve the CitriSurf passivation system for use on their parts.”
These are just a few of the comments from our customers who are using the CitriSurf cleaning and passivation system in their metal cleaning process and stainless steel passivation. It may seem so simple to get this kind of results from the “orange juice acid”, but the results in the field have substantiated that it works better, faster, safer, and more economically than the old nitric acid system.
Citric Acid Passivation of Stainless Steel
Products Finishing, May 1999
The benefits of using Citric Acid for passivation
Passivation of Stainless Steel
Products Finishing, November 1998
Though the author only describes passivation with nitric acid, he gives a good explanation of the process
How To Passivate Stainless Steel Parts
Modern Machine Shop, October 2003
A good overview of passivation
Products Finishing, April 2010
Another good overview of passivation