Fraunhofer Introduces Pickling Self-adhesive Tape for Pre-treatment of Metal Surface

A new self-adhesive tape simplifies the process of pickling aluminum surfaces. It is safer than existing treatment methods involving pickling pastes, sprays or baths, because there is no rinsing stage and hence no need for complicated wastewater disposal.

Application of pickling tape prior to the repair of damaged paint. The paint has been removed by mechanical abrasion and the pickling tape is used for pre-treatment of the metal surface. After removal of the tape and simple cleaning with a damp cloth, the surface is ready to receive a fresh coat of paint.

Aluminum is a light metal used wherever low weight is a prime consideration. Traditionally used in aircraft construction, it is increasingly employed in other sectors such as automotive engineering. But as a base metal, aluminum requires protection against corrosion, which is usually achieved by a special paint or other surface coating. Adhesive bonding is becoming increasingly popular as a means of joining lightweight metal components. But aluminum cannot be coated or bonded without an appropriate pre-treatment to remove undefined deposits of oxides, hydroxides or other contaminations that are almost always found on technical aluminum surfaces. Pickling is one of the most common techniques employed for this purpose. It involves immersion of the components in a solution of chemicals that dissolves the contaminants and provides a perfectly clean metal surface.

The use of a pickling bath is difficult when dealing with large components that only require treatment of part of their surface, or when components are being reworked or repaired. Local pre-treatment methods are increasingly preferred in such cases. Manufacturers mainly use pickling agents in paste or spray form, which are spread or sprayed onto the metal surface manually by trained technicians. The problem is that the chemicals employed are strongly acidic or alkaline. Consequently, the surrounding areas of metal have to be carefully masked off. A subsequent rinsing stage is required to remove the pickling agent, and the corrosive wastewater has to undergo special treatment prior to disposal. "None of the currently available local pre-treatment solutions is entirely satisfactory. Thats what led us to the idea of developing a pickling tape that can be easily applied to the areas that require pre-treatment," says Dr. Malte Burchardt of the Adhesion and Interface Research department at the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Bremen, describing IFAMs approach.