Published on 20/11/2020 by Aldo Bordiga
Nickel is a naturally occurring metallic element with a silvery white, lustrous appearance. It is the 24th most common element on earth and occurs widely distributed in the rocks of the earth’s crust and core.
Nickel is a metal that has ubiquitous distribution on the earth’s surface; it is found in trace amounts almost everywhere and is necessary for the human organism for its biological functions. Nickel is absorbed through food, particularly vegetables, which contain a higher or lower percentage of it depending on the type and area of cultivation.
Like many other substances, authorities have defined a safe intake limit for nickel through food and water.
More information on the risks of oral nickel intake can be found from EFSA, the European Food Safety Authority. It updated its risk assessment document for nickel in food and drinking water on September 24, 2020. The document can be found on the following page, Update of the risk assessment of nickel in food and drinking water .
In Europe, the use of materials in contact with food is regulated by FCM Regulation (EC) No. 1935/2004, which specifies in Article 3:
Materials and articles, including active and intelligent materials and articles, shall be manufactured in compliance with good manufacturing practice so that, under normal or foreseeable conditions of use, they do not transfer their constituents to food in quantities which could: a) endanger human health; or b) bring about an unacceptable change in the composition of the food; or c) bring about a deterioration in the organoleptic characteristics thereof.
Speaking specifically about electroless nickel plating, it is often used as an alternative to stainless steel on parts of food processing machinery, based on steel, aluminum, and brass.
There are mainly two causes by which a material can release substances to a food item:
Electroless nickel plating, especially the high-phosphorus type Niplate 500, has a high chemical resistance in contact with many substances. The coating is normally not degraded by dry foodstuffs, oily or greasy substances and neutral aqueous solutions.
On the other hand, the electroless nickel coating can transfer Ni2+ ions to the food depending on various conditions, e.g:
If we talk about coffee machines, for example, a nickel plated fitting will not release nickel as much as a boiler, since the contact surface for the fitting is small and the contact time short, while boiling water can sit for days in the boiler and, if the boiler is nickel plated, nickel migration can occur in unacceptable quantities.
The electroless nickel, like all metals in general, is sensitive to acidic substances, and in particular to oxidizing acidic substances, although its ability to resist corrosion and consequent dissolution is superior to galvanic nickel plating and many other metals.
Electroless nickel has a very high hardness of 500 to 1000 HV depending on the heat treatment carried out. Its hardness exceeds that of nitrided steels. This is why it has a very high resistance to adhesive and abrasive wear.
Electroless nickel coatings therefore perform very well with regard to the release of substance through mechanical wear. Their high hardness and wear resistance mean that in many applications, the release of substance to the foodstuff in this manner is negligible.
Even in this case, the machine designer must still assess the working conditions of the part to be coated.
Our electroless nickel coatings NIPLATE® 500, NIPLATE® 600 and NIPLATE® 500 PTFE are approved for food contact according to NSF 51. The standard establishes certain minimum hygiene and food protection requirements for materials used in the construction of machinery for food production or processing. Compliance with this regulation does not replace the need to assess legislative compliance by the economic operator placing the good on the market.
Given the multiplicity of variables involved, it is not possible for the plating supplier to determine beforehand the compliance of the coating with contact with specific foods.
The manufacturer of the item that is nickel plated or contains a nickel plated part must verify that the nickel release is within the limits set by the legislation of the reference country in which it is placed, performing appropriate migration tests.
For further information please refer to our declaration D031 - Declaration for the use of food contact coatings
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