The proposed project focused on the validation of a TSAA process, including pre- and post-treatment, which is defined by the topic manager, and its implementation in industrial scale. An existing industrial plant, which was be selected by the topic manager, was benchmarked with respect to the number and dimensioning of the components of the plant and its periphery with respect to the technical requirements for the process. The process itself was performed in laboratory- and pilot scale to verify the reproducibility of the process for given aluminium alloy(s) and to characterise and quantify the properties of the surface of specimens after each step of the TSAA process.
Failure mode analyses, such as FTA (failure tree analysis), DRBFM (Design review based on failure mode) and FEMS (Failure modes and effects analysis) will be performed. Knowledge-based analysis of the process and the relevant parameters, such as temperature and filtration, as well as the aforementioned failure mode analysis, will lead to the definition of process sheets and risk assessment plan. Environmental analysis of the process will consider chemicals used – also with respect to REACh compliance -, exhaust fumes (especially in the working area), waste and waste water output. As far as possible, recycling routes for process waters and chemical components will be analysed and suggested. Risk analysis will also include possible health risks in the working area, which can originate from incorrect use of chemicals or waste.
The results of the analysis of environmental and health risks will be included into the process sheets and risk assessment plan. Data and process-relevant knowledge gained during the aforementioned analysis steps will finally lead to elaboration of a manufacturing plan and compilation of a Process procedures and standard manual.
The ValidateTSAA project focusses on the validation of a TSAA process, including pre- and post-treatment, and its implementation in industrial scale. An industrial plant, selected by the topic manager, was benchmarked with respect to the number and dimensioning of the components of the plant and its periphery with respect to the technical requirements for the process. The process itself was performed in laboratory- and pilot scale to verify the reproducibility of the process for given aluminium alloy(s) and to characterise and quantify the properties of the surface of specimens after each step of the TSAA process. Failure mode analyses, such as FTA (failure tree analysis), DRBFM (Design review based on failure mode) and FEMS (Failure modes and effects analysis) were performed. Knowledge-based analysis of the process and the relevant parameters, such as temperature and filtration, as well as the aforementioned failure mode analysis, have led to the definition of process sheets and a risk assessment plan. Environmental analysis of the process has considered the chemicals used – also with respect to REACh compliance -, exhaust fumes (especially in the working area), waste and waste water output. As far as possible, recycling routes for process waters and chemical components were analysed and suggested. Risk analysis included possible health risks in the working area, which can origin by incorrect use of chemicals or waste. The results of the analysis of environmental and health risks were included into the process sheets and risk assessment plan. Data and process-relevant knowledge gained during the aforementioned analysis steps have finally led to elaboration of a manufacturing plan and compilation of process procedures and standard manual.
Project Context and Objectives:
Concept and project objective(s)
The Tartaric Sulphuric Acid Anodizing (TSAA) is promoted as a potential alternative to chromic acid anodizing (CAA) by aircraft manufacturers. Prior to industrial applicability of this technology, a validation step in order to reach TRL6 is required, providing engineering, manufacturing and operational readiness including value and risk assessment. The following objectives have to be met in this project. The work packages of the working plan are chosen in such a way to ensure that these objectives will be met:
The main objectives of the project are:
1. to develop the process procedures and standard manual for the industrial application of TSAA
2. to validate the whole process including pre-treatments and post-treatments defined by the Topic Manager
3. to compile a technical and economic study of the new TSAA technology as compared to the established chromic acid anodizing process
In order to meet these objectives the following detailed activities have to be carried out in the ValidateTSAA project:
Ad 1: Development of process procedures and standard manual (for details see work packages 2, 4, 7)
The manual will contain the following issues / thematic areas: Scope and limitations of the process, classification, references to literature, patents and normative standards; definitions, technical requirements, including materials, equipment, preparation of solutions, operating conditions, maintenance and regeneration, procedure of anodizing, pre- and post-treatment, local repair of anodizing, stripping of anodizing, testing procedures, quality assurance provisions, safety issues.
Ad 2: Validation of the whole process (for details see work packages 5, 6)
The Process validation will include a pre-production qualification testing. These tests are to determine the conformance to the technical requirements of the process procedure in real industrial conditions.
Definition of the pre-treatments
- Alkaline cleaning
- Alkaline etching
- Acidic pickling
Definition of post-treatments
- (Low temperature) Sealing
- Conversion layer
Qualitative and quantitative testing of TSAA layers:
- Total coverage, smooth, and aesthetically pleasing
- Excellent substrate-coating (paint) adhesion
- Applicable after Cr free surface preparation (e.g. cleaning, desmutting, etc.)
- Repairable (local touch up)
- Wettability (contact angle / surface energy) of the cleaned surface according to DIN 55660-2
Anodized film dimensions:
- Anodic film weight (tested according to EN 12373-2)
- Film thickness (tested according to ISO 2360 and by SEM on a cross section)
- Number of pits/dm2 and pits exceeding 0.8 mm diameter (tested in accordance with ISO 9227)
- Compatible with REACh
- Process, control and testing safe for environment and workers
- Overall process sustainability
- Proper treatment of chemicals, waste and waste waters
- Initial training
- Continuous education of workers
- Definition of process data sheets
- Failure tree analysis (FTA)
- Design review based on failure mode (DRBFM)
- Failure mode and effects analysis (FMEA)
Ad 3: Compilation of a technical and economic study of the new TSAA technology (for details see work package 1, 3)
- Evaluation of the state of the art
- Technical impact of the new technology
- Cost / performance evaluation
- Cost analysis with recurring and non-recurring costs (RC & NRC)
- Minimum conditions for viability of the TSAA process
Because the TSAA Validate project is linked to the parallel running ChromFree Project (Clean Sky Project 325883), both, Deliverable 1.1, 2.1 and D3.1 have been delayed by one month each in accordance with the topic manager to await some results from the ChromFree which are considered to be required input data and because the required samples AA 2024 were sent only in November 2013.
The alloy to be treated with the process has been decided to be AA2024 in accordance with the topic manager during the kick-off meeting. When different alloys, e.g. AA219x type aluminium-lithium alloys, are to be treated, it would be necessary to adapt the process parameters (and possibly one or more process baths) accordingly, which is not planned to be done in the scope of this project.
The onsite structures and possibilities at HAI have been assessed. In evaluation of the production site of HAI the current anodizing facility is unable to house the new line. Therefore an alternative building has been evaluated together with HAI, namely the already existing building 41 at HAI in Schimatari. According to HAI, the largest part to be treated is the so-called “Big Skin” with dimensions of 3300 mm (L), 2030 mm (H) and a thickness of 1.8 mm (sheet). Based this size requirement, and taking into consideration the larger (compared to the old facility), but still limited available space in building 41, the technical and work-safety requirements of the process, production requirements, plant periphery and flow of material and products, a new line has been designed with a two-line configuration and a transition system between the two lines. This line has also been designed to include the capacity of performing alternative pre-treatment steps (e.g. for treating different alloys), as well as for three alternative sealing steps, namely hot-water sealing, Cr(VI)-free conversion coating and classical sealing processes (e.g. Alodine 1200).
Additionally, limits of process temperatures and cycle times, as well as the requirements for plant periphery have been defined in the scope of WP1 (see also Deliverable D1.1)
In the scope of work package 2 process limits regarding process time and temperature, bath concentration and electric parameters during anodizing have been benchmarked by means of test runs. For comparison SEM micrographs of aluminium AA2024 surfaces treated at standard, minimum and maximum conditions have been presented in D2.1. The benchmarking runs yielded the following results:
• Inhomogeneous and porous surface of the untreated AA2024, which may have negative influence on the quality of the treated goods. Therefore an incoming goods inspection is necessary to ensure good quality without pores.
• Alkaline degreasing (Metaclean T2001): High porosity of the surface at maximum values (50 g/l, 70 °C, 30 min). It is not recommended to use parts treated at these conditions. At standard concentration and temperature conditions, there is no major risk up to an immersion time of 30 min.
• Alkaline etching (Aluminetch No.2) results in a micro structured surface with some adhering smut. At the lower limits the microstructure is finer than at the upper limits.
• Acidic Pickling (Turco SmutGo NC): After pickling the specimens exhibit a porous surface which is free from smut. At the lower limits the surface is smoother with smaller pores; at the highest limits deep pores are present. An immersion time of 10 minutes is not recommended at or near the maximum concentration. Because of the pickling effects on fatigue behaviour, it is mandatory to respect the limitation of 10 min component immersion time in bath.
• Anodizing (TSAA): At lower and higher limits for bath concentration, anodization voltage and steepness of the voltage ramp, as well as at the lower temperature limit, no major differences compared to the specimen anodized with standard conditions have been observed. At a temperature of 39 °C larger pores are observed, so an anodization at this temperature is not recommended. An overrun procedure to deal with failure or overrun of certain parameters is given in D2.1, Table 18.
• Hot water sealing: Within the limits (30 to 60 minutes at 95 °C) longer sealing results in a better morphological appearance of the surface.
In the scope of work package 3, economic calculations regarding the TSAA process have been performed. These calculations include technical and economic impact (including calculation of required energy, water, chemicals...), cost/performance evaluation, the minimum conditions to make the technology viable and the definition of the efficiency potentials for the running process. T
Work package 4 (D4.1) gives considerations concerning chemical hazards, contingency measures, waste and waste water treatment and exhaust air management, including a calculation of the required air flow for each active tank. It has to be stated that it lays in the responsibility of the user always to refer to up-to-date material safety datasheets and local regulations when dealing with chemicals and wastes thereof. Details can be found in D4.1 (appendix 4).
Work package 5 gives a detailed risk-assessment plan, based on FTA (fault tree analysis), FMEA (failure modes and effects analysis) and DRBFM (design review based on failure mode). Detailed results and action plans are given in D5.1 (appendix 5)
FTA analyses fault trees, where various basic failure modes (“events”), such as “wiring failure”, which are connected by logical operators, lead to a TOP event, such as “no anodization layer”. Four different Top events have been identified:
• no anodization layer
• inhomogeneous layer
• too thin anodization layer
• bad properties of the layer
The fault trees are given in deliverable D5.1 (appendix 5).
FMEA (which assumes a 100% final inspection of the anodized parts) lists potential failure modes and analyses the importance of each of the failure modes: First, each failure mode is rated concerning its probability P (from “extremely unlikely” to “frequent”), its severity S (from “hardly observable” to “catastrophic”) and its detection probability D (from “certain” to “unlikely”), see also the following table. The importance of a failure mode is given by the Risk Priority Number RPN which is calculated by RPN = P*S*D. If for a certain RPN <100, the need for action is not necessary, but acceptable. If RPN ≥ 100, then an action is required for mitigation.
The results of FMEA are listed in detail in D5.1. Two risks with an RPN > 100 have been identified: The outcome is that there are two failure modes which require additional action for mitigation:
- If the concentration in the etching chemistry is too high, the surface will be over etched and be porous. Therefore the bath composition has to be checked after regeneration of the bath, because this is the only way that the concentration can be too high.
- If the temperature in the TSAA bath is out of range, the anodization layer will have a bad quality. Since this failure is hard to detect, a second temperature sensor in the bath should be installed. This sensor has to be connected to the controlling PC which gives an acoustic alarm if the temperature is out of range. In this case an employee has to check the bath for errors in the heating/cooling system of the bath and the first temperature sensor and to take measures to bring the temperature back into the allowed range.
Detailed evaluation of risks concerning parameters of each bath, based on the results of the experiments performed in D2.1, are given in chapter 2 of D5.1 (appendix 5). They are rated by risk (from “hardly observable” to “catastrophic”) and occurrence (from “extremely unlikely” to “frequent”).
Serial checks and minimum checking frequencies are listed in detail in D5.1. Detailed actions for quality assurance are given in chapter 4 of D5.1 (appendix 5). Details on risks and counter-measures concerning health and environment issues as well as safety issues for workers are given in chapter 5 and 6 of D5.1 (appendix 5).
In the scope of work package 6, the process has been performed on pilot scale by Happy Plating. No changes of the parameters were necessary, i.e. the optimum parameters as described in D2.1 were used. In general there is no difference in the mounting of the parts compared to other anodization processes as used at HAI at the moment. Details can be found in D6.1 (appendix 6).
In the scope of work package 7 a standard manual containing process procedures and specifications has been provided (D7.1, Appendix 7.1). Besides general information on the process and quality specifications for rinsing waters, the manual contains the following points and specifications for each active bath:
7. Technical Requirements
8. Quality Assurance Provisions
Furthermore, quality requirements and specifications for quality checks and inspections for the baths and for the treated specimens are given.
A training session, composed of theoretical and practical sessions, with HAI personal has been performed on 01.07.2014 – 02.04.2014. The Agenda is given below. The following points have been explained, discussed, respectively trained in practice:
• Performance of the single process steps on the Happy Plating coating plant
• Definition of process parameters and exposition times for each single step
• Explanation of cleaning and rinsing requirements
• Definition of requirements and necessary HAI production plant adaptions
• Explanation of process maintenance and analysis routines
• Training in solution preparation
• Explanation of risk and health issues
• Definition of critical quality criteria
The TSAA training programs were attended by Konstantinos Mousoutzanis and Epameinondas Ioannou from Hellenic Aerospace Industry.
The anodized part has been characterized by layer thickness measurement (eddy current and FIB) and by SEM.
The anodised layer is very compact and homogenous with a layer thickness of 2.9 to 3.4 µm, but scratches which are on the substrate before anodising are still visible after anodising. Therefore the substrates have to be without any mechanical damage (incoming goods inspection)!
A report on the training session (D7.2) has been provided
General Strategic impact of the project Validate TSAA
One major focus of the technological competition in aeronautics is the increased use of novel superior light-weight materials processed in ECO friendly manufacturing. Clean Sky contributes to technological and scientific leadership in the area of aeronautics light-weight design, and therewith strengthens the competitiveness of the European industry. The processes developed in the scope of ValidateTSAA have high performance potentials for anodizing steps using environmentally friendly chemicals fulfilling the REACh requirements. Within the ValidateTSAA project, the employment of ECO friendly anodization processes including pre- and post-treatment was thoroughly studied, analysed and future applications in the aircraft production processes were considered and developed in great detail.
Exploitation and dissemination of foreground obtained in the project Validate TSAA
The dissemination and exploitation of project results were performed in WP8, under the supervision of the project coordinator (PC). The WP leader of WP8 was responsible for the release of documentations and reports and its updates during the course of the project. The PC has further coordinated the exploitation activities and synergies within the project partners CEST and Happy Plating and particularly among similar topics and topics depending on surface-treatment of lightweight metals.
Exploitation of project results by the Validate TSAA project partners:
The Topic Manager has been systematically informed on the proposed work progress in order to support the final implementation of project results in their company. The major partner foreseen further and capable for exploitation on a commercial scale was the project partner Happy Plating. This company is well equipped to provide plating services for the aeronautical industry once the Chromium free surface pre-treatment and sealing process has been fully developed in the project Validate TSAA.
Happy Plating is within its core competence interested in the industrial implementation of highly know-ledge based electrochemical processes in the field of surface technology for various applications. This is including anodic oxidation processes from classical DC anodisation towards pulsed anodisation processes towards pulsed plasma electrolytical anodisation. The reference in aeronautic industry gained by this project will enlarge the field of business especially in up-scaling and implementation helping Happy Plating to strengthen its position as European market leader for such services.
Additionally the new technology developed gives rise to a broad variety of possible applications simultaneously introducing an environmentally friendly chrome free process route. The high-end European surface finishing industry as well as electronic and automotive industry will be addressed as possible customers. The deep scientific and technical understanding for anodic (pulse) processes gained within this project was helping Happy Plating successfully working with customers in different fields of surface technology.
The project results of ValidateTSAA have enlarged the understanding, knowledge and capabilities of CEST concerning the surface treatment of Light metal alloys. CEST will exploit its increased competence in other research projects with other aeronautical partners for the benefit of the European aeronautical community.
Dissemination of the foreground project results obtained in the project Validate TSAA
Project results have been disseminated at two levels: detailed and general. At the detailed level informal information, deliverables and technical reports have been produced and have been distributed to the Topic Manager. Those reports describe all the technical details and the conclusions of the research and are marked confidential.
At the general level, a book chapter with the title “Pre-treatment and anodizing processes for an improved corrosion protection of aluminium 2024-T3 alloys” for the Advanced Material book series, Editor Professor Tiwari is in preparation and a part from the project results regarding pretreatment and TSA anodization will be presented at the EUROCORR 2014 in Pisa.
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