REACH - Applications for authorisation AFA043-01 Chromium trioxide

Closed 10 Jul 2023

Opened 15 May 2023


Public consultation on alternatives

Reference: AFA043-01

Boeing Distribution (UK) Inc
MacDermid Performance Solutions UK Ltd

Application type: Initial

Substance name:

Chromium trioxide (CT) (includes “Acids generated from chromium trioxide and their oligomers", when used in aqueous solutions)

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

Proposed use: Inorganic finish stripping 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 surface treatment processes.

To protect, or improve the performance of, the metallic substrate, there are a number of different inorganic coatings that may be applied to the surface of a component.  Though inorganic coatings are applied for specific purposes, it is essential that the finish can also be removed. The removal of a coating or surface finish from a substrate is known as stripping. The stripping of anodised layers, conversion coatings or hard chrome plating with chromium trioxide-based solutions may be used as a surface pre-treatment step to remove the finish  as part of Maintenance, repair and overhaul (MRO) work or for rework, when surface finishes are non-confirming or must be removed for quality testing. Stripping using chromium trioxide can also be used as part of a main treatment to remove copper plating used to mask new components in the carburising process. The key function of the chromates in inorganic finish stripping is: To ensure negligible or no effect on the underlying substrate whilst supporting the efficient removal of the inorganic finish.

The applicants have identified a shortlist of potentially suitable alternatives. However, due to 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 20 sites in 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): ERC 6b,
  • Process category (PROC): PROC 0, PROC 5, PROC 8b, PROC 9, PROC 13, PROC 15, PROC 28
  • Product category (PC): PC 14
  • Article category related to subsequent service life (AC):
  • Technical Function: other:  To ensure negligible or no effect on the underlying substrate whilst supporting the efficient removal of the inorganic finish

Annual tonnage used:

  • <20 tonnes/annum

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).


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