Applications for authorisation AFA074-01 - Chromium Trioxide

Overview

Public consultation on alternatives

Reference: AFA074-01

Applicant: SCA Ceramic Coatings Ltd

Application type: Initial application

Substance name: Chromium trioxide

• EC Number: 215-607-8
• CAS Number: 1333-82-0
• Annex 14 Entry Number: 16

Proposed use: Use of chromium trioxide in a binding/sealing process applied to porous/semi-porous coatings to achieve a wear and corrosion resistant technical ceramic surface to meet specific performance characteristics.

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

Treatment of components used in Oil & Gas drilling equipment and associated components using slurry coating and sealing products containing chromium trioxide; to enhance wear resistance, corrosion resistance, chemical resistance and adhesion to components to produce a smooth finish with the purpose of creating a coating to meet specific performance characteristics. The treatment is also used to seal porosity in thermal spray-coatings as used in the Steel Industry.

In simple terms, the Slurry mix is an aqueous chromic acid solution containing various crystalline filler materials. The Slurry mix is applied to the surface to be coated; the coated component is transferred into an oven where the parts are soaked at temperature to convert the chromic acid into a ceramic binder which holds the filler materials in place.

The resulting cured Slurry coating is porous and extremely friable at this stage so is subsequently treated by applying a chromic acid solution to the surface. This is then oven cured to convert the chromic acid into a technical ceramic.

When oven-cured, hexavalent chromium (CrVI) is reduced to trivalent chromium (CrIII), insoluble chromium oxides and hydroxides are formed and these contract to form microscopic scales.

The Sealing process is completed after multiple cycles, and the resultant finished coating is an inert, chromium-rich, technical ceramic with crystalline filler where the chromium creates a continuous, protective layer.

This specialised coating/sealing method is specified by the End Users who hold the Design Authority and are responsible for R&D activity. The End Users have already undertaken testing to identify potentially suitable alternatives, none of which currently satisfy the performance requirements therefore the applicant is seeking a review period of 12 years to allow time for alternatives to be identified and developed.

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): 0, 4, 8a, 9, 10, 13, 28
• Environmental Release Category (ERC): ERC6B
• Technical Function (TF): Binder; layer thickness; wear resistance; corrosion resistance; chemical resistance

Annual tonnage used: <1 Tonne/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).