Nitriding for Food-Safe Applications

Nitriding has proving to be a reliable surface treatment for food-safe applications. Nitriding can enhance the surface properties of materials, making them ideal for the demanding environments of food processing equipment where durability, cleanliness, and safety are paramount.

Why Nitriding is Suitable for Food-Safe Applications

Nitriding processes improve the surface hardness, wear resistance, and corrosion resistance of metal components without significantly altering the core material properties. Here’s why these processes can be used in food-safe applications:

1. Approval for Food Contact

Salt Bath Nitrocarburizing has been examined by various regulatory bodies^{1 2 3}, including the U.S. Department of Health & Human Services¹. These entities have confirmed that the nitriding process does not pose a food additive risk and are safe for use in food-contact applications. Additionally, European testing by the Kantonales Labor Zurich² and Institut Nehring GmbH³ has validated that parts treated with Salt Bath Nitrocarburizing release no harmful substances, making them safe for contact with non-acidic foodstuffs.

2. Non-Leaching and Non-Toxic

A primary concern for food-safe applications is whether treated surfaces release harmful substances. Studies on Nitriding have shown that the process results in no detectable levels of cyanide or other harmful chemicals. As a result, nitrided surfaces pose no risk of contaminating food products if proper procedures are followed.

3. Enhanced Surface Performance

In food processing, where surfaces often come into contact with sticky or abrasive substances, nitriding provides critical benefits. Nitrided surfaces have improved lubricity, reducing friction and preventing food products from sticking to equipment. This is particularly important for processing machinery such as mixers, slicers, and molds, where cleanliness and ease of operation are key. Additionally, nitriding's anti-galling properties help prevent wear from repetitive metal-on-metal contact, making the surfaces more durable under heavy use.

Applications in Food Processing

Nitriding is applicable in various food processing contexts:

• ‍Cutting Blades: Nitrided blades maintain sharpness for longer, ensuring precise cuts and reducing downtime for maintenance. At Nitrera we have nitrided meat cutting tools, and tremendous quantities of medical marijuana trimming blades.  ‍
• Mixers and Extruders: The non-stick properties of nitrided surfaces prevent food pastes, dough, and other substances from adhering to equipment, improving efficiency and hygiene. At Nitrera we have nitrided food extrusion dies.  ‍
• Conveyor Systems: Nitrided components resist wear and corrosion, making them suitable for continuous use in environments that handle non-acidic food products.

Considerations and Limitations

While nitriding is suitable for non-acidic foods, it is important to note that nitrided surfaces may not be ideal for contact with acidic foods. For food processing applications involving high acidity, polishing away the nitrided materials black oxide surface layer before use, or alternative surface treatments may need to be considered.

Conclusion

Nitriding is a reliable surface treatment for certain food-safe applications, offering superior wear resistance, corrosion resistance, and non-toxicity. With validation from both U.S. and European regulatory bodies, nitriding can be safely used in environments that process non-acidic foods. Businesses can benefit from the extended lifespan, ease of cleaning, and improved performance that nitrided surfaces provide, making them an ideal choice for enhancing food-processing equipment.

References:​

1. US Department of Health & Human Services (September 1988)

An enquiry was answered as follows: “Based upon the information you have provided on your MELONITE/QPQ process, we would not consider this ingredient and the other ingredients in your formulation to result in a food additive situation when used in the nitriding of steel. We would therefore have no objection to the use of the chemicals in your process when used to treat steel that will be used in equipment that contacts food.”

2. Kantonales Labor Zurich / Switzerland (December 1988)

After examining TUFFTRIDE Q and TUFFTRIDE QP treated samples the Canton Laboratory wrote: “The release of cyanide in the three mediums water, 1n NaOH solution and 4 % acetic acid are below the detectable limit of 0.01 mg/dm2. There are no objections to the use of such steel parts in food machines, as long as it is guaranteed that residues of ‘dewatering fluid’ are removed prior to first use.”

3. Institut Nehring GmbH, Braunschweig (December 1994)

Test rods made from material C 45, 18 mm in diameter and 150 mm long were subjected to a migration test after being treated by the TUFFTRIDE QPQ treatment. The examination and performing of the migration tests were carried out in accordance with EG guidelines with the following results: “According to the results of the tests, on contact with nonacidic foods such as meat, fish and grain a hazardous transfer of substances from the nitride layer on the metal surface of equipment or machine parts which have been TUFFTRIDE QPQ treated is not to be expected.“

The above assessments confirm the safe use of TUFFTRIDE QPQ treated parts with foods, when they do not come into contact with acidic media.”

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