REACH Compliant Hexavalent Chrome Replacement for Corrosion Protection

Lead Research Organisation: University of Manchester
Department Name: Materials

Abstract

Metal corrosion and wear currently costs industry $1.5-2 trillion globally per annum. The basis of many systems to mitigate these problems utilise compounds containing hexavalent chromium (Cr6+) as used in: chromic acid anodising (CAA); chemical conversion coatings; primers; paint, and hard chrome plating (EHC). Corrosion and wear are of particular importance to the aerospace industry where protection requirements are extremely severe. European REACH legislation is expected to ban the use of Cr6+ containing materials by 2016 due to its carcinogenic properties. This is a critical issue for
the aerospace industry and has been highlighted as a priority in the 2011 National Aerospace Technology Strategy. A number of attempts have been made to introduce Cr6+ free materials and processes. The solutions have been found not to be as robust as expected, due in part, to the lack of validated, accelerated testing methods, resulting in unexpected failures. Individual aerospace companies are developing their own, proprietary solutions. This has caused problems in the supply chain, which it is finding difficult to support. This bid addresses this situation by bringing together an integrated aerospace based team from SMEs to academia to identify innovative solutions and develop robust accelerated testing methods that accurately reproduce severe environmental applications. This will enable the sector to adopt a common approach to the development and testing of REACH compliant protection systems including new processes. The technical approach to address this problem has been defined by the consortium including industrial, supply chain and academic
partners. The approach has 6 key objectives:

(1) Benchmark existing corrosion, wear and adhesion testing methods
modifying these to better represent service conditions; (2) Based on the knowledge developed in (1) ,develop new test where gaps are identified; (3) Test Cr6+ based solutions through the tests specified in (1) and (2) to establish a baseline and test potential Cr6+ free solutions through the same matrix to establish deviation from the baseline; (4) Where the alternate solution is better than current the product it will be characterised in terms of its chemistry and microstructure to provide a scientific explanation for its performance. The consortium would then quantify the variation of the production system to evolve a product that consistently meets the protection requirements; (5) Where the alternate solution performs badly a root cause analysis by the universities will be carried out to determine the weaknesses and identify the
improvements necessary to create a viable alternate. This knowledge will be fed back the material supplier and applicator to enable them to formulate new protection and application systems that address the identified weaknesses, and; (6) New
CAA and EHC replacement processes will be developed to mitigate the risk of failure of the industrially-selected solutions. In terms of benefits, the consortium OEM's and first tier companies will specify the new coatings for use on their products. Those who have their own processing facilities will also set up the capability to produce the new coatings. The specialist processing companies will be able to set up facilities to provide these coatings and to provide the materials these process will require. Additionally, new areas of academic research will be opened up, thus strengthening the science base. A
succesful project will result in the removal of Cr6+ surface coatings from the operating environment. This will address the environmental concerns and reduce operating costs. The materials testing protocols will lead to reductions in materials testing costs and shorter time to market for future coatings. The consortium will investigate the possibility of incorporating the outputs into standards. Where appropriate, the outputs will be protected and suitable IP arrangements will be part of the consortium agreement.

Planned Impact

This project is capable of delivering impact as it brings together a team including academia, SMEs and OEMs in the aerospace sector, in a fully integrated, structured, science-based, systems approach to the development of testing methods and materials processes in an area that has traditionally been developed on an empirical basis. This has not been attempted before in this area and will result in innovative test methods, materials and processes being developed and a significant up skilling of the sector. This approach will capture this knowledge in a useable form for the future and makes it
widely available outside of the aerospace sector. In terms of measurable impact, the main beneficiaries from the proposed study will initially be the consortium OEM's and first tier companies that are within the aerospace sector. As best practice in terms of testing is disseminated and more widely adopted, then other industries will benefit from the standardised and reliable corrosion and wear test methodologies generated from this research. Such materials testing protocols will lead to reductions in materials testing costs and shorter times-to-market for future coatings. The validation of Cr6+ free coatings will impact upon both the aerospace and, also eventually, other key industrial sectors such as automotive and defence that also require similar processes. Key benefits to the aerospace sector will be the specification of new coatings for use on
their products. Those who have their own processing facilities will be able to set up the capability to produce the new coatings. The specialist processing companies, including SMEs, will be able to set up facilities to provide these coatings and to provide the materials these process will require. A successful project will result in the removal of Cr6+ surface coatings from the operating environment which will address the environmental concerns and reduce operating costs. This research will work towards the aim of the elimination of Cr6+ by 2016, as currently proposed under REACH. The
proposed project represents an opportunity for the UK aerospace industry to become leaders in the area of Cr6+ replacement through the development and demonstration of an innovative common testing programme and materials and process. This research will be underpinned by a science-based understanding at leading universities and acentralised materials data management architecture. This research will also lead to the potential for development of alternative Cr6+ processes in the partner universities by understanding the failure mechanisms of existing candidates.

Publications

10 25 50
 
Description The research has assessed the suitability of measurement of corrosion rates of aluminium alloys, following various surface treatments designed to confer corrosion protection, using an electrochemical method. This method provides a numerical ranking of corrosion resistance of the variously treated surfaces. It provides a ranking in a much shorter test time than the salt spray test method which is the main test method currently used in industry. The project has also assessed the effectiveness of new anodizing procedures developed at Manchester University for protection of aluminium alloys against corrosion. Comparisons with existing anodizing processes has revealed an improved performance from use of the new treatments. Industry parners are evaluating the new anodizing process for corrosion protection and adhesive bonding.
Exploitation Route Others may adopt the new methods of anodizing and of testing of corrosion resistance.

The electrochemical noise method will be employed in a follow on TSB project, which will focus on conversion coatings.

This project has now commenced led at Manchester by Dr Michele Curioni.
Sectors Aerospace, Defence and Marine,Transport

 
Description REACH programme on chromate conversion coating replacements 
Organisation BAE Systems
Country United Kingdom 
Sector Private 
PI Contribution This is a follow up REACH programme which focuses on conversion coatings, rather than the anodic coatings of the completed programme. The team is examining the performance of a range of commercial conversion coating treatments to identify their merits in comparison with traditional chromate conversion coatings.
Collaborator Contribution The research involves electrochemical testing, corrosion testing and analytical investigations of conversion treated aluminium alloy. A key aim is to rank performances and to assess their short-term and long-term protection of the alloy.
Impact None yet as work still in progress.
Start Year 2017
 
Description REACH programme on chromate conversion coating replacements 
Organisation Bombardier Inc.
Country Canada 
Sector Private 
PI Contribution This is a follow up REACH programme which focuses on conversion coatings, rather than the anodic coatings of the completed programme. The team is examining the performance of a range of commercial conversion coating treatments to identify their merits in comparison with traditional chromate conversion coatings.
Collaborator Contribution The research involves electrochemical testing, corrosion testing and analytical investigations of conversion treated aluminium alloy. A key aim is to rank performances and to assess their short-term and long-term protection of the alloy.
Impact None yet as work still in progress.
Start Year 2017
 
Description REACH programme on chromate conversion coating replacements 
Organisation General Electric
Country United States 
Sector Private 
PI Contribution This is a follow up REACH programme which focuses on conversion coatings, rather than the anodic coatings of the completed programme. The team is examining the performance of a range of commercial conversion coating treatments to identify their merits in comparison with traditional chromate conversion coatings.
Collaborator Contribution The research involves electrochemical testing, corrosion testing and analytical investigations of conversion treated aluminium alloy. A key aim is to rank performances and to assess their short-term and long-term protection of the alloy.
Impact None yet as work still in progress.
Start Year 2017
 
Description REACH programme on chromate conversion coating replacements 
Organisation Loughborough University
Country United Kingdom 
Sector Academic/University 
PI Contribution This is a follow up REACH programme which focuses on conversion coatings, rather than the anodic coatings of the completed programme. The team is examining the performance of a range of commercial conversion coating treatments to identify their merits in comparison with traditional chromate conversion coatings.
Collaborator Contribution The research involves electrochemical testing, corrosion testing and analytical investigations of conversion treated aluminium alloy. A key aim is to rank performances and to assess their short-term and long-term protection of the alloy.
Impact None yet as work still in progress.
Start Year 2017
 
Description REACH programme on chromate conversion coating replacements 
Organisation Monitor Coatings Ltd
PI Contribution This is a follow up REACH programme which focuses on conversion coatings, rather than the anodic coatings of the completed programme. The team is examining the performance of a range of commercial conversion coating treatments to identify their merits in comparison with traditional chromate conversion coatings.
Collaborator Contribution The research involves electrochemical testing, corrosion testing and analytical investigations of conversion treated aluminium alloy. A key aim is to rank performances and to assess their short-term and long-term protection of the alloy.
Impact None yet as work still in progress.
Start Year 2017
 
Description REACH programme on chromate conversion coating replacements 
Organisation Poeton Industries Limited
PI Contribution This is a follow up REACH programme which focuses on conversion coatings, rather than the anodic coatings of the completed programme. The team is examining the performance of a range of commercial conversion coating treatments to identify their merits in comparison with traditional chromate conversion coatings.
Collaborator Contribution The research involves electrochemical testing, corrosion testing and analytical investigations of conversion treated aluminium alloy. A key aim is to rank performances and to assess their short-term and long-term protection of the alloy.
Impact None yet as work still in progress.
Start Year 2017
 
Description Dissemination of results to parners of TSB REACH Compliant hexavalent chrome replacement for corrosion protection 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Presented data on new approaches to anodizing of aerospace aluminium alloys for chromium replacement and new approaches to testing of corrosion resistance using electrochemical noise measurements. The audience included major aerospace and surface treatment industries.

The new anodizing procedure is being further assessed by industry, eg by inclusion in fatigue testing of anodized alloys.
Year(s) Of Engagement Activity 2014