Applications for authorisation AFA051-01 Chromium trioxide surface treatment

Closed 22 Sep 2023

Opened 28 Jul 2023


Public consultation on alternatives

Reference: AFA051-01

Applicant: Surface Engineering Association Chromium Trioxide Authorisation Consortium (8 companies – see names on application documents)

Application type: Initial

Substance name: Chromium Trioxide

EC number: 215-607-8

CAS number: 1333-82-0

Proposed use: Use of chromium trioxide for the surface treatment of engineering components, mainly for the aerospace and defence sector, with the purpose of creating a coating to meet specific and critical performance characteristics.

Broad information on use applied for (conditions of use and function): These coatings can be broken down into four categories – chromate conversion coatings, passivation of stainless steel, chromic acid anodising and sealing after anodising. 

 All the companies involved in this application carry out sub-contract surface treatment processes and typical components that require surface treatments for this use are components that are part of landing gear, flap tracks, access doors, cargo areas, seat tracks, engine intake area, defence vehicles etc. 

These processes represent the surface treatment of metal components with a water-based chromium trioxide mixtures to deposit either a complex chromate conversion / passivation  coating using a simple immersion process or an aluminium oxide coating and the sealing of the coating through the anodising process. 

In simple terms, anodising is the process of using the aluminium as an anode within an electrolyte bath. When a cathode is positioned within the anodising tank and a current passed through the solution, the oxygen reacts with the surface of the aluminium creating an anodic layer. The longer the aluminium is in these conditions, the thicker the protective layer. The oxide layer is then sealed in a separate immersion process. Immersion coatings are simple processes where the components are immersed in a water-based solution of chromium trioxide in order to produce a chemical reaction on the surface that produces a complex chromate coating. No electrical current is involved with these immersion coatings. 

This application covers the use of chromium trioxide for critical performance surface treatment processes at 8 separate Companies and carried out on a sub-contract basis.

List of descriptors:

  • Life cycle stage (LCS): Use at industrial site  
  • Sector of end Use (SU): 0 (Other: manufacture of products for automotive and other applications)  
  • Product Category (PC): 14 (Metal surface treatment products)  
  • Process Category (PROC): 1, 4, 8a & 8b, 13, 28  
  • Environmental Release Category (ERC): ERC6B  
  • Article Category related to subsequent service life: N/A  
  • Technical Function (TF): Surface treatment agent 

Annual tonnage used: between 1 and 2 tonnes

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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