Nitric Acid/Hydrofluoric Acid Mixtures
Hydrofluoric acid/nitric acid mixture is clear liquid with an acidic odor. The mixture is made in different concentrations and used to prepare the surface of implantable medical devices for the application of bioactive coatings. Implantable devices are often made from titanium, stainless steel or Nitinol (NiTi) and must be etched to improve the surface texture for proper coating adhesion. Achieving 100 percent adhesion of bioactive coatings is imperative, as this is what allows the device to properly attach to bone or living tissue and prevent the body from rejecting an implant.
Mixtures containing Hydrofluoric acid and nitric acid are used to clean and etch the surface of various implantable medical devices including:
- Bone plates
- Dental implants
- Pins and screws
- Rods and bars
- Spinal fusion cages
Hydrofluoric and Nitric Acid Mixtures for Etching Titanium and Other AlloysHydrofluoric acid and nitric acid mixtures are highly effective at etching titanium, Nitinol, and stainless steel. Mixtures containing 3% hydrofluoric acid are the most common ratio used, and etch rates increase as the nitric acid concentration increases.
Etching titanium with hydrofluoric acid alone is a slow process and produces a by-product of hydrogen gas. Adding nitric acid increases the etching rate, eliminates the formation of hydrogen gas, and produces a smoother surface finish. Without the nitric acid present, the titanium surface is very rough and nodular. As the nitric acid concentration increases, the surface roughness decreases to the point of creating a slight electro-polished surface that is almost reflective.
Etching Titanium and Dental ImplantsEtching titanium with HF and nitric acid blends produces hexafluorotitanic acid, nitrogen dioxide, and water. With this solution, the HF tends to be more stable, the hydrogen gas is eliminated, and the etch rate increases. We offer different chemical concentrations of N+HF blends based on the required specification or on the desired effects of on the etch rate and surface finishes.
Achieving the Desired Thickness for Etching TitaniumSelect a ratio based on your material type, shape, and surface. The higher the ratio of nitric acid, the higher the etching rate. Etching rates can also vary depending on the fluid temperature and material being processed.
Examples of typical etching rates for titanium:
- Mixtures containing 3% hydrofluoric acid and 3% nitric acid provides an approximate etching rate of 8.92µ (0.351 mils) per minute.
- A mixture of 3% hydrofluoric acid and 10% nitric acid provides an approximate etching rate of 24.51µ (0.97 mils) per minute.
- Mixtures with 3% hydrofluoric acid and 15% nitric acid provide an approximate etching rate of 27.08µ (1.07 mils) per minute.
Medical device manufacturers often require a specific hydrofluoric acid and nitric acid mixtures based on what the FDA approved during the prototype and testing stage. All our chemical mixtures are made to order and available in off-the-shelf concentrations or in custom ratios based on your requirements. Hydrofluoric acid and nitric acid mixtures are offered in 4L (1 gal.) and 20L (5 gal.) plastic containers. We also provide 220L (55 gal.) drums fitted with color-coded drip tubes that easily connect to existing equipment.
Important Safety Precautions for Using Hydrofluoric Acid and Nitric Acid MixtureThe caustic nature of hydrofluoric acid and nitric acid mixtures poses a serious health risk to anyone who works with the solution. Inhaling the vapors can cause a sore throat, coughing, breathing issues, and lung inflammation or congestion. Skin contact causes severe burns. If the solution penetrates the skin, it can cause deep tissue and bone damage. Eye contact may also cause severe burns or permanent eye damage.
Symptoms of HF exposure are often delayed for several hours. If you suspect you may have been exposed to HF contained in the Nitric and HF Blends but are not experiencing any immediate symptoms, apply immediate first aid, nonetheless. A quick response can substantially reduce injury.
Prevent injury by taking these precautions whenever you work with hydrofluoric acid and nitric acid mixtures:
- Preparation: Read and fully understand the Safety Data Sheet (SDS) for hydrofluoric acid and nitric acid blends. Next, review or create a Standard Operating procedure (SOP) for the process where you are using the solution. Finally, obtain a Calgonate first aid kit and spill kit.
- Create a Designated Area: Nitric and HF Blends should always be handled inside of a fume hood or, under forced ventilation, with a sign stating “Danger, Hydrofluoric Acid Used in this Area”. Post your SOP in or near the designated area.
- Wear Protective Clothing: This includes laboratory coats, acid resistant aprons, long pants, closed-toe shoes, goggles, face shields, vapor respirators, and gloves.
- Safe Processing Practices: Always follow safe processing practices for hydrofluoric acid and nitric acid mixtures. Never use the blend after-hours or while working alone. It is also important to ensure that all containers and chemically compatible and clearly labeled.
- Storage and Handling: Proper storage and handling of hydrofluoric acid and nitric acid mixtures are critical. Containers should be stored and transported in an upright position and securely supported so they cannot tip over. All tanks should be covered when not in use or under forced ventilation to prevent vapor inhalation.
- Disposal: Hydrofluoric acid and nitric acid should also be treated as hazardous waste and sent to an RCRA approved facility for disposal.
View the full list of safety precautions, protective wear requirements, and first aid procedures: Working with Nitric and HF Blends.
Learn More About Our Hydrofluoric Acid and Nitric Acid MixturesNuGenTec offers nitric acid/hydrofluoric acid mixtures in several ratios and can provide customized mixes upon request. We also other off-the-shelf and custom precision cleaning solutions for applications including semiconductor and medical device manufacturing.
Request a quote today or contact us to discuss your unique needs.