5 Benefits of Citric Passivation
You’re probably aware of the conundrum facing industrial stainless steel applications. When you want to fully protect the chromium oxide layer in your stainless steel products, you have a decision to make: Should you go with nitric passivation or citric passivation?
Stainless steel surfaces can be made highly resistant to corrosion if and only if they are effectively cleaned and passivated prior to use, otherwise, once a corrosion site has started, it will only get worse, being continuous and self-catalyzing. Normal fabrication processes and wear-and-tear will destroy this passive chromium oxide layer anywhere that high physical force, certain chemical reactions, heat, electrical current or abrasion occur.
So, what are the main benefits of citric acid passivation? Let’s dive in.
1. Handling: Citric Passivation Is Safer to Use
JAYCO’s citric acid passivation chemistries have proven to be a vast improvement over the traditional nitric acid formulations and give you a safe stainless steel citric acid passivation process. 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.
Nitric acid requires high temperatures and high concentrations, up to 160*F and up to 55 percent concentration by volume. This makes nitric acid passivation extremely aggressive, presenting potential risk factors to the equipment, the environment, human operators and sensitive parts being passivated.
By comparison, citric acid applications can be run at lower temperatures (from ambient to 120*F), diluted to much lower concentrations (4 to 10 percent by volume) and for less time, making them much safer. Citric acid is naturally occurring and generally considered “edible” and “food-grade,” presenting a much less hazardous profile than nitric acid.
2. Emissions, Disposal, Temperatures
With citric passivation, there are no toxic gas emissions, the disposal process is easier and the solution poses no dangers at high temperatures. Citric acid is generally regarded as safe (GRAS) and, as mentioned before, is commonly used in many foods and beverages. This means that JAYCO’s citric acid passivation chemistry solution is compatible with the environment and can most often be disposed into sanitary sewage systems with minimal waste treatment to meet current environmental agency approvals.
On the other hand, nitric acid offers significant personnel hazards, creates toxic and corrosive gasses, and costly waste treatment is necessary after its application. The waste treatment process can expose the user to long term liability under regulatory agencies and cost the company disposing of it some serious cash.
3. Ventilation Is Not Required
The reason why citric passivation doesn’t require ventilation while nitric passivation does has to do with the different chemical properties of the two acids. Nitric acid is a strong oxidizer and can release harmful nitrogen oxides (NOx) fumes when it reacts with a stainless steel surface. These fumes can cause respiratory irritation and other health problems if inhaled in large amounts.
On the other hand, citric acid is a weak acid and doesn’t produce harmful fumes when it reacts with stainless steel. Citric passivation is considered to be a safer and more environmentally friendly process. It doesn’t require the same level of ventilation as nitric passivation.
That being said, it’s still important to follow proper safety protocols when working with any chemicals, including citric acid. Operators could be advised to wear personal protective equipment, work in a well-ventilated area and properly dispose of any waste materials.
4. Increased Operational Efficiency
Citric acid is a weaker acid than nitric acid, and doesn’t react as aggressively with the stainless steel surface, meaning it requires less time to dissolve and remove any surface iron or other contaminants that can cause corrosion. The process can be performed at lower temperatures than nitric acid passivation. Increasing the temperature associated with the passivation process decreases the overall processing time per ASTM 967, AMS 2700, and other specs.
Because citric acid is comparatively weak against nitric acid, it doesn’t dissolve the stainless steel surface, resulting in less waste material to dispose of.
5. Cost Savings
Citric acid passivation offers several cost savings over nitric acid passivation, which can make it a more cost-effective solution for treating stainless steel. Here are five places you can save money with the process:
- Lower chemical costs: Citric acid is a cheaper alternative to nitric acid, which can save you money on passivation chemicals.
- Reduced waste treatment costs: Citric acid produces less waste than nitric acid, meaning the cost of treating and disposing of the waste generated during the process is lowered.
- Lower energy costs: Lower temperatures than nitric’s higher temperature requirements translate to less energy required to heat up the solution and a lower energy bill.
- Reduced maintenance costs: Since citric acid is less corrosive than nitric acid, it is less likely to damage equipment and machinery used during the passivation process, extending the life of your tools.
- Improved efficiency: As mentioned earlier, citric acid passivation can be performed more quickly than nitric due to the weaker nature of the acid, meaning more parts can be processed in less time.
Additional Benefits
JAYCO’s proprietary formulations of citric acid geared towards stainless steel passivation deliver additional benefits for our customers.
- Passive layers equal or greater to nitric acid.
- Inhibited microbial growth without the use of added biocides.
- Improved ultrasonics cavitation, as well as very high rinsability (reduced DI/RO water consumption).
- Effective use with automated process controls, which includes monitoring and dosing systems.
Putting It All Together
Citric acid is the latest modern solution for stainless steel passivation. Being safer, easier to handle, more environmentally friendly, and overall less demanding to use, citric acid wins out on practically every front when compared with nitric acid. By using special formulations targeting your application’s specific requirements, JAYCO’s citric acid passivation chemistries can accomplish passivation levels comparable to nitric blends in a much safer, biocide-free, employee-conscious way.
JAYCO Chemical Solutions is North America’s single-source provider of engineered cleaning solutions. From process analysis and application engineering to delivery and support, JAYCO improves operations for precision metal, medical, optical, UHV, space/aerospace and general manufacturing customers. For more information on JAYCO Chemical Solutions, our products and our markets, please call us at (814) 593-0022, or email us at info@jaycochem.com.
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