Applications for authorisation AFA073-01 - Chromium Trioxide

Overview

Public consultation on alternatives

Reference: AFA073-01

Applicant: Centronic Limited

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 for the electroplating of components for Geiger-Muller tubes with technical performance requirements with the purpose of creating a coating to provide specific performance characteristics and to match existing components.

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

Industrial use of chromium trioxide for the electroplating of components for Geiger-Muller tubes (GMTs) with technical performance requirements, with the purpose of creating a coating that provides specific performance characteristics and enables replacement and production of components that match existing product specifications.

A Geiger-Muller tube is a gas-filled radiation detector used to detect and measure ionising radiation including alpha particles, beta particles, gamma rays and X-rays. The tube contains an anode and cathode within a gas-filled enclosure. Halogen-quenched GMTs contain chlorine or bromine gases which improve detector performance and service life but are highly corrosive to metallic internal components.

Chromium trioxide is used to electroplate an internal metallic chromium layer onto steel cathode components. The deposited chromium is subsequently oxidised during an oxygen plasma treatment to produce a stable chromium oxide surface layer. This chromium oxide layer provides corrosion resistance against the halogen gases present within the tube and maintains the functional performance characteristics of the detector throughout its service life. 

The chromium coating provides a hard, smooth, chemically inert and corrosion-resistant surface, reducing degradation of internal components and preventing changes to detector performance caused by interaction between halogen gases and metallic surfaces. Without the chromium-derived oxide layer, absorption of quench gases and deterioration of detector characteristics would significantly reduce product performance and operational lifetime. 

The plating process is undertaken on internal steel cathode components using controlled electroplating baths operated at ambient temperature. The process includes loading components onto jigs, immersion in chromic acid plating baths, rinsing, drying and subsequent oxygen plasma treatment. The resulting chromium oxide surface is integral to the technical function and long-term reliability of the finished Geiger-Muller tube.

List of descriptors:

• Life cycle stage (LCS): Use at industrial site
• Sector of end Use (SU): SU16 - Industrial uses: uses of substances as such or in preparations at industrial sites
• Product Category (PC): PC 14 - Metal surface treatment products, including galvanic and electroplating products
• Process Category (PROC): PROC 1, PROC 13, PROC 8b, PROC 28
• Environmental Release Category (ERC): ERC 6b
• Article Category related to subsequent service life: Not applicable
• Technical Function (TF): Plating agent / surface treatment agent

Annual tonnage used: 0.2 – 0.25 tonnes per year

Review period requested: 12 years

How to submit comments

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