Applications for authorisation AFA071-01 - CT

Overview

Public consultation on alternatives

Reference: AFA071-01

Applicant: Tata Steel UK Ltd

Application type: Review report

Substance name: Chromium trioxide (CT)

• EC Number: 215-607-8
• CAS Number: 1333-82-0

Proposed use: The use of chromium trioxide for the manufacture of electrolytic chromium coated steel (ECCS).

Broad information on use applied for (conditions of use and function):

The applicant uses chromium trioxide at its site in Llanelli, Wales (the Trostre Works) for the manufacture of electrolytic chromium coated steel (ECCS). The substance is used to apply a thin layer of chromium and chromium oxide onto flat metal products (steel surfaces) by electrolytic deposition. The resulting coating is free of chromium trioxide and in turn provides a surface for excellent adhesion for a subsequent functional organic (lacquer or laminate) layer. The applicant’s products are then used by their customers to produce food packaging (cans for food and drink) and various other types of metal packaging.

Cr(VI) is supplied to the production process as chromium trioxide flakes to make the electrolyte solution. The process itself is highly automated and contained. Operators are involved in sampling and analysis of the electrolyte solution and wastewater via dedicated sampling systems, dissolving chromium trioxide flakes into the circulation tanks, performing control rounds and undertaking maintenance activities. Comprehensive technical, administrative and organisational risk management measures are in place to minimise exposure to workers and emissions to the environment.

Chromium trioxide plays a critical role in the production of ECCS – the structured layers of chromium metal and chromium oxide, together with the applied organic coating, provide the required corrosion and chemical resistance during the lifecycle of the packaging material. In particular, for food and beverage packaging, the use of chromium trioxide:

• provides a highly chemical and corrosion-resistant surface that protects the underlying steel from reacting with the contents of the can, which could otherwise lead to contamination of the food or drink, posing health risks and compromising the integrity of the product.
• enhances the adhesion of a subsequent organic coating, which acts as a further barrier between the metal and the food. This dual-layer system ensures that the food remains uncontaminated and preserves its intended taste, texture and nutritional value over extended shelf lives.
• contributes to the mechanical strength and formability of the steel strip, which is important during the can manufacturing process to prevent defects that could compromise the seal or structure of the can.

Eight overarching requirements have been identified for evaluating suitable alternatives to chromium trioxide in the electrolytic process used to form metallic chromium (Cr(0)) and trivalent chromium (Cr(III)) layers on steel:

1. Corrosion resistance of the steel plate prior to use
2. Adhesion, i.e. a suitable surface for organic coating application
3. Chemical resistance to the contents of the packaging
4. Compatibility with downstream processes, including heat resistance and formability
5. Suitability for food contact (in compliance with food contact regulations)
6. Visual properties, including aesthetics, brightness, and overall appearance
7. Scalability and stability of the production process for high-volume manufacturing
8. Sustainability, in particular, the ability to recycle

The applicant’s substitution efforts are currently focused on Cr(III)-based alternatives which are considered to be the most promising. However, Cr(III)-based alternatives, as with all other alternatives identified, currently fail to meet necessary performance criteria and thus are not technically feasible. Alternative coatings do not provide the high performance of coatings deposited from chromium trioxide in terms of chemical and corrosion resistance, adhesion and food safety compliance. Many substitutes either fall short in durability or are not yet fully validated for long-term food contact. This would lead to increased risk of can failure, reduced shelf life and potential food safety issues.

Additional information on the use applied for and the production process is given in the Chemical Safety Report (CSR) and Analysis of Alternatives (AoA).

Operational Conditions (OCs) and Risk Management Measures (RMMs) are described in the CSR and OC/RMM summary table.

Information on key functionalities of chromium trioxide for plating is given in the AoA.

List of descriptors:

• Life cycle stage: IS (Use at industrial sites)
• Sector of end use (SU): 15 (Manufacture of fabricated metal products, except machinery and equipment)
• Environmental release category (ERC): 5 Use at industrial site leading to inclusion into/onto article
• Process category (PROC): 1, 8b, 9, 13, 28, 0
• Product category (PC): 14 (Metal surface treatment products)
• Article category related to subsequent service life (AC): N/A
• Technical Function: Plating agent

Annual tonnage used: 100 - 150 tonnes/year

Review period requested: 15 years

How to submit comments

Provide some basic information on possible alternative(s) in the online survey below but more detailed information should be provided in document(s) prepared using the commenting templates in the related section below. A “public version” should always be completed and will be published after the consultation has closed. If you want to include confidential information in your submission, please additionally complete a “confidential version” and submit both versions as attachments.

The consultation lasts for 8 weeks (unless otherwise specified) and closes at 23:59 London time (BST).