REACH – Applications for authorisation AFA028-01 - Chromium trioxide

Closed 19 May 2023

Opened 24 Mar 2023


Public consultation on alternatives

Reference: AFA028-01


Boeing Distribution (UK) Inc
Henkel Ltd
MacDermid Performance Solutions UK Ltd
Wesco Aircraft EMEA Ltd

Application type: Initial

Substance name: Chromium Trioxide – (includes “Acids generated from chromium trioxide and their oligomers", when used in aqueous solutions).

EC Number: 215-607-8

CAS Number: 1333-82-0

Proposed use: Anodising using Chromium trioxide in aerospace and defence industry and its supply chains.

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

Chromium trioxide is used in the aerospace and defence industries (comprising of the civil aviation, defence/security, and space industries, along with aeroderivative products). It is a key component in chromic acid anodising (CAA); an electrolytic oxidation process where the surface of a metal is converted to an oxide which has desirable functional properties. This creates a hard protective insulating metal oxide layer on the surface of components. This gives key functions including wear resistance, corrosion resistance, chemical resistance, adhesion promotion (adhesion to subsequent coating or paint), and layer thickness. Impact upon fatigue strength, and inter-granular attack/end-grain pitting are important performance requirement considerations in the selection of alternatives. These performance requirements supplement the aforementioned key functions delivered by chromium trioxide.

The applicants have identified a shortlist of potentially suitable alternatives. Due to the complexity of design challenges, performance requirements, safety requirements and regulatory controls that must be tested for each listed alternative, and the need for industrial implementation in the whole supply chain, the applicant is seeking a review period of 12 years.

This “applied for use” involves the continued use of chromium trioxide across approximately 30 sites across Great Britain (GB).

List of descriptors:

  • Sector of end use (SU): 0 -Other: Aerospace and defence industry and its supply chains
  • Environmental release category (ERC): 5
  • Process category (PROC): PROC 0, PROC 5, PROC 8b, PROC 9, PROC 10, PROC 13, PROC 15, PROC 21, PROC 24, PROC 28 
  • Product category (PC): 14: Metal surface treatment products 
  • Article Category related to subsequent service life (AC): N/A 
  • Technical Function: Wear resistance; Corrosion resistance including active corrosion inhibition ("self-healing"); Chemical resistance; Adhesion promotion (adhesion to subsequent coating or paint); Layer thickness

Annual tonnage used: 

  • 10-35 tonnes/year

Review period requested: 12 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).


  • Applications for authorisation


  • Registration, Evaluation, Authorisation & restriction of CHemicals (REACH)