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Borate Free Cleaners for Aluminum Alloys

Final Report Summary - BFCLEANER (Borate Free Cleaners for Aluminum Alloys)

Executive Summary:
The project was realized by the company Italtecno (http://www.italtecno.com) and the University of Bologna-Manufacturing Technology group (http://www.unibo.it/docenti/luca.tomesani) . The project analysed four new borate-free agents (cleaners), able to remove any grease or solid soils adsorbed or chemically bonded to the surface of components from previous manufacturing operations like forging, rolling, casting, machining or extrusion. Two innovative cleaners were specially developed by Italtecno for the project. Different borate-free chemicals (the two from Italtecno and two commercial) were tested and investigated evaluating the cleaning efficiency compared to formulations containing borates and also evaluating the impact in term of corrosion of these new formulations on two aluminium alloys widely utilized in aeronautics (2024 clad and unclad). Together with the identification of the optimal cleaner and its processing window the project provided indications on the analytics to be performed on the bath and the limiting values for selecting bath maintenance or replacement of the full solution. A couple of new efficient borate free agents able to remove contaminants with an higher efficiency of borate base agents were found, moreover the new agents demonstrated optimal cleaning efficiency also at low temperatures thus providing a new interesting ecological savings in term of energy and CO2 emission for bath temperature control.
Project Context and Objectives:
Most anodizing plants are using a degreasing step as the first step of the anodizing process. The degreasing is generally performed in a medium alkaline solution and rarely in an acidic solution. The degreasing products actually on the market generally contain borate. Borate must be limited in the waste water coming out from the plant since they are not permitted in discharged water. The anodizing plants generally are equipped with a physical-chemical waste water treatment plant. However, this type of plant is not able at all, or with a very limited capacity, to remove borate from waste water. At a recent European Diagnostics Manufacturing Association (EDMA) Meeting, several new additions to the Substance of Very High Concern (SVHC) candidate list in relation to the Registration, Evaluation, Authorization and restriction of Chemicals Regulations 2007 (REACH) were discussed. The registration and review completed as part of REACH has meant the current classification of Boric Acid CAS 10043-35-3 / 11113-50-1 as of 1 December 2010 will be listed as H360FD (May damage fertility. May damage the unborn child).
When cleaning aluminum parts, there are two major tasks and one main hazard:
1. To remove any grease or solid soils adsorbed or chemically bonded to the surface of the parts from previous operations.
2. To remove the surface oxide film together with these contaminants.
3. The risk of damaging/corroding material surface thus reducing mechanical proprieties and particularly fatigue life
The type of surface soils on extrusions, laminates and castings are usually oils, greases, associated solids e.g. polishing abrasives, lubricants and greases from handling equipment, cutting and blanking operations, contamination related to transport, etcetera.
Solvent and vapor degreasing is likely to largely disappear in the near future because of the implementation of the Montreal Protocol. All of the grease-type soils can be removed by solvent degreasing, thus leaving a dry surface; as a degreasing system, solvents are easy to use but they have several disadvantages:
- All solvents are toxic to some extent and can also be addictive in quite low concentrations.
- They leave the work dry, but not readily wettable.
- They may leave solids behind and once these solids are separated from the supporting grease, they become very difficult to remove.
Other types of degreasers are acid and alkaline cleaners. Alkaline cleaners are more used than acid cleaners in anodizing. Usually formulations for cleaners use borates. Since borates have been recently reclassified as toxic, the research for borate-free products has become a priority for the aluminium industry.

The project analysed four new borate-free agents (cleaners), able to remove any grease or solid soils adsorbed or chemically bonded to the surface of components from previous manufacturing operations like forging, rolling, casting, machining or extrusion. Two innovative cleaners were specially developed by Italtecno for the project. Different borate-free chemicals (the two from Italtecno and two commercial) were tested and investigated evaluating the cleaning efficiency compared to formulations containing borates and also evaluating the impact in term of corrosion of these new formulations on two aluminium alloys widely utilized in aeronautics (2024 clad and unclad). Together with the identification of the optimal cleaner and its processing window the project provided indications on the analytics to be performed on the bath and the limiting values for selecting bath maintenance or replacement of the full solution. A couple of new efficient borate free agents able to remove contaminants with an higher efficiency of borate base agents were found, moreover the new agents demonstrated optimal cleaning efficiency also at low temperatures thus providing a new interesting ecological savings in term of energy and CO2 emission for bath temperature control.
Project Results:
Almost all cleaners appear as effective as reference one, with two of them evidently producing an higher efficiency.Visual Inspection appears as the best qualitative evaluation parameter while % of removed material and droplet on grease seems to be the most reliable quantitative parameters for evaluation of cleaning efficiency. Lastly, if the conditions are restricted to the low temperature levels (below 50°C) for energy savings aspects and a visual inspection level of grease removal of 3 is set the following conditions are obtained: again the two best chemicals are able to provide a very good cleaning efficiency also at very low temperature and reduced immersion times.
The limits and the methodology for bath maintenance or replacement with selected agents was investigated for the chemicals under development by Italtecno. The results were included in the product data sheet.
The data on the efficiency of the whole process chain when any contaminations between adjacent bath solutions occurred was included in technical data sheets of the agents as limits for maintenance or replacing of the bath for Italtecno Cleaners. Concerning Removal Rate Testing, generally unclad specimens are more subjected to etching effect. The Reference agent has a minor cleaning effect and, as consequence, it produced also the minimal removal rate for both clad (0,0007 µm/min) and unclad (0,0014 µm/min) specimens. Concerning one best agent, it produced the maximum Removal Rate when maximum concentrations were used (both on clad and unclad) while lower values were found at minimal concentrations. The other best agent showed an average behavior in term of Removal Rate between reference and Agent 1 and a minor influence of concentrations is evidenced. It has also to be noted that the suggested range of concentration variability between the agents are very different (around 70% of variability for one and 30% for the other) thus affecting the data distribution. It has finally to be reminded that the Agent 1 passed the preliminary evaluation only when maximum and intermediate concentrations were adopted, while the Italtecno agent provided a good behavior also at lower concentrations especially when the efficiency was evaluated through the droplet test.

Potential Impact:
The most part of anodizing plants are using a degreasing step as the first step of the anodizing process. The degreasing is generally performed in a medium alkaline solution and rarely in an acidic solution. The degreasing products actually on the market generally contain borate.
Borate must be limited in the waste water coming out from the plant since they are not permitted in discharged water. The anodizing plant generally are equipped with a physical-chemical waste water treatment plant. However this type of plant is not able at all, or with a very limited capacity, to remove borate from waste water. At a recent European Diagnostics Manufacturing Association (EDMA) Meeting several new additions to the Substance of Very High Concern (SVHC) candidate list in relation to the Registration, Evaluation, Authorisation and restriction of Chemicals regulations 2007 (REACH) were discussed. The registration and review completed as part of REACH has meant the current classification of Boric Acid CAS 10043-35-3 / 11113-50-1 as of 1 December 2010 will be listed as H360FD (May damage fertility. May damage the unborn child.).
The aim of the present research is to eliminate borate from alkaline degreasing product to be used in the majority of anodizing plants. If a new efficient borate free agent able to remove contaminants with the same or higher efficiency of borate base agents will be found without providing any reduction in mechanical proprieties of the treated parts, then the project will be able to completely fulfill the requirements of the call. Indeed, it must be noted that borate in anodizing plants are used exclusively in the degreasing process and therefore the elimination of borate from this process will eliminate borate from anodizing plant completely.

List of Websites:
No website creation was required for this call.