Chrome plating is a popular surface finishing technique used across various industries for its attractive finish and corrosion resistance. Chrome plating is commonly used on food contact surfaces like blades, rollers, and utensils in food processing. However, there are important safety considerations regarding using chrome plating in food applications.

Chrome Plating

Chrome plating, also known as hard chrome plating, is an electroplating process that applies a thin layer of chromium onto a metal surface. The chromium layer is extremely hard and provides excellent wear and corrosion resistance.

Some key benefits of chrome plating include:

High hardness and abrasion resistance
Corrosion and chemical resistance
Attractive mirror-like surface finish
Can be applied to complex geometries
Cost-effective process

Chrome plating is applied using an electrolytic process where the part to be plated is immersed in a chromic acid bath and an electric current is applied. The thickness of the chrome layer can range from 0.25 microns to hundreds of microns.

While both decorative and functional chrome plating exists, hard chrome plating tends to deposit much thicker chromium layers for enhanced wear and corrosion resistance.

Chrome plating is extensively used in the automotive, aerospace, metalworking, food processing, printing, and other manufacturing industries. The food processing industry leverages the durability and corrosion resistance of chrome plating for various food contact surfaces.

Chrome Plating Applications in Food Processing

Chrome plating has become ubiquitous in food processing due to its useful properties. Some of the common applications of chrome plating in the food industry include:

Food Processing Equipment

Doctor blades – These are blades used to scrape processing surfaces clean and are often chrome plated. The hard chrome coating prevents material buildup and corrosion.
Extruder barrels, screws, dies – Chrome plating provides abrasion resistance and prevents corrosion by acidic food products.
Mincers, grinders, slicers – The cutting blades and surfaces are chrome plated to resist wear and corrosion.
Conveyors, guides, bearings – Chrome plating creates low-friction surfaces for smooth conveyance of food products.
Valves, pumps, fittings – The wet surfaces are chrome plated for corrosion protection from liquids.
Rollers on dough sheeters – Chrome coated steel rollers smoothly flatten dough without sticking.
Mixer bowls – While uncommon, chrome bowls resist staining and abrasion. Stainless steel is more popular.

Food Serving Items

Serving spoons, spatulas, tongs – These utensils feature a chrome plated surface for easy cleaning and corrosion resistance.
Chafing dishes, serving trays – Chrome plated for appearance and to prevent corrosion by food.
Cutlery baskets, pot racks – Chrome coated wire provides corrosion resistance and an attractive look.

Food Processing Surfaces

Table tops, counter tops – Chrome plated surfaces allow easy cleaning and prevent corrosion.
Sinks, drain boards – Chrome plating provides water and corrosion resistance.
Storage racks, shelving – Chrome coated shelves resist corrosion and add a clean look.

Is Chrome Plating Safe for Food Contact Surfaces?

While chrome plating provides many useful properties, its safety for direct food contact requires careful evaluation. There are a few key factors to consider:

Chrome Plating Process Impurities

The chrome plating electrolytic process utilizes chromic acid along with various additives. Trace amounts of these chemicals can potentially leach into foods if the chrome plating layer is porous or damaged. These may include:

Hexavalent chromium – Toxic and carcinogenic even in small amounts
Nickel – Allergen for those with nickel sensitivity
Cadmium, lead – Toxic heavy metals
Organic additives – Contaminants

Properly processed chrome plating ensures minimal impurities. Food-grade plating processes validate the purity of the deposited chrome layer.

Chrome Plating Wear and Damage

Chrome platings are extremely thin – even a few microns. Over time, the plating can wear off through abrasion or get damaged by cuts and impacts. This exposes the nickel underlayer which can then corrode or leach into food.

Regular inspection and prompt refurbishment is necessary. Worn or damaged chrome plated surfaces should be identified and promptly re-plated.

Porosity in Plating

Microscopic pores in the chrome layer provide a pathway for chemicals and corrosion to reach the base metal below. This can lead to contamination of food if the base metal or nickel underlayer corrodes.

High quality plating processes minimize porosity. Careful process control ensures the chrome layer has high density with minimal pores.

Electrolytic Rusting Underneath

If the chrome plated surface gets damaged, moisture and cleaning agents can seep through. This allows corrosion of the underlying base metal which could potentially leach into food.

Proper pre-treatment is vital. The base material must be properly cleaned and prepared to prevent subsurface corrosion under the chrome layer.

Safety Tips for Chrome Plated Food Contact Surfaces

While chrome plating provides many benefits, it requires careful implementation to ensure food safety:

Use high quality processes – Validate plating purity, density, and adhesion to minimize impurities and pores.
Pre-treat properly – Thoroughly clean and prepare base material before plating to prevent subsurface corrosion.
Inspect regularly – Check for wear, damage, flaking and refurbish promptly to avoid food contamination.
Clean thoroughly – Use non-abrasive cleaners and sanitize fully to remove grime and bacteria without damaging plating.
Avoid corrosion – Prevent moisture buildup and galvanic corrosion especially if base metal is dissimilar.
Get regulatory approval – Ensure compliance with food safety regulations for direct food contact surfaces.

By following these guidelines, the risks of chrome plating can be minimized for safe use in food processing.

Chrome Plating Regulations for Food Contact

With growing awareness of food safety, regulations exist in many countries to control the use of chrome plating in food contact items. These aim to minimize the risk of hazardous substances leaching into foods.

United States FDA Regulations

The FDA Food Code regulates materials used for food contact surfaces. Key requirements for chrome plating include:

Conform to ASTM standards – Chrome plating must adhere to ASTM International standards for corrosion resistance.
Minimal hexavalent chrome – Limit of 0.1 μg/cm2 hexavalent chromium allowed on food contact surfaces.
No nickel leaching – Nickel release should be below the limit of 0.5 μg/cm2/week.
Meet NSF standards – NSF International standards dictate purity requirements for food service chrome plating.

European Union Regulations

The EU framework regulation 1935/2004 controls materials in contact with food. Specific requirements for chrome plated articles are:

Pre-treatments validated – Pre-plating processes must not contaminate base material.
Conform to EN standards – Must comply with European EN standards for release limits.
No hexavalent chromium – Hexavalent chromium release should be below 0.01 mg/kg food.
Documentation provided – Manufacturer must provide documentation proving safety.

International Standards

ISO 20807:2018 – Limits hexavalent chromium in chrome plated food contact surfaces to 0.1 μg/cm2.
AS/NZS 4020:2005 – Australian/New Zealand standard limits hexavalent chromium to 0.1 μg/cm2.
GB 4806-2016 – Chinese standard has release limits for lead and cadmium from chrome plated articles.

Options for Food Grade Chrome Plating

For food contact applications, specialized food grade chrome plating processes are used to ensure safety:

Electroless Nickel Undercoating

Electroless nickel plating is applied before chrome plating.
Much purer than electroplated nickel with minimal leachable impurities.
Provides better corrosion resistance than electroplated nickel.
More expensive process than standard electroplated nickel.

Trivalent Chrome Processes

Utilizes trivalent chromium instead of hexavalent.
Trivalent chromium has lower toxicity than hexavalent.
Limitations exist on thickness and corrosion resistance.
More complex process requiring tight control.

Microdiscontinuous Chrome Plating

Uses proprietary chemical additives.
Minimizes porosity by slowing plating speed.
Achieves denser and more impervious layer.
Requires extensive process validation.

Physical Vapor Deposition (PVD)

Evaporates chromium metal which is then deposited on surface.
Provides an extremely pure chromium coating.
Excellent corrosion resistance and density achieved.
Highly expensive specialized process.

Best Practices for Safe Use of Chrome Plating in Food Processing

To leverage chrome plating safely in food environments, processors should follow these best practices:

Conduct a hazard analysis to identify high risk applications. Avoid direct food contact where feasible.
Select reputable plating companies with experience in food grade processes. Request safety documentation.
Establish incoming inspection procedures to verify food grade plating quality.
Implement preventive maintenance and inspection schedules to promptly identify damaged plating.
Follow plating manufacturer instructions for proper cleaning methods. Avoid abrasives.
Train staff on hygienic practices for plated machinery and utensils.
Adhere to applicable regulations and standards for chrome plating in food contact items.
Maintain records to trace plated items and conduct recalls if contamination is suspected.

Conclusion

Chrome plating provides useful properties like corrosion resistance and durability that make it invaluable for the food processing industry. However, the potential risks of chemical leaching into food require careful evaluation and control.

By utilizing high purity plating processes, establishing proper preventive controls, training staff, and adhering to food safety regulations, processors can safely leverage chrome plating in food contact applications. Careful implementation allows the benefits of chrome plating to be realized while minimizing the risks of food contamination.