Surface Preparation Guide
Highest strength structural bonds are obtained when parts are free from oils, greases, paints, oxide films, dust, mold release agents, rust inhibitors and other contaminants. The amount of surface preparation to be carried out depends directly on the required bond strength, the desired durability to environmental service conditions and the cost of surface preparation.
The three major methods for removing surface contaminants are degreasing, chemical cleaning and abrasion. They may be used alone or in combination for greater effectiveness depending on the degree of surface cleanliness required. A preferred sequence of surface preparation methods to give highest bond strengths comprises abrasion followed by degreasing and chemical etching. A recently developed promising alternative is plasma etching.
Degreasing can be carried out with solvents such as acetone, isopropanol or proprietary cleaners including hot alkali solutions. Surfaces should be free of rust, paint, mill scale, etc. Degreasing alone is used where maximum bond strength or outdoor durability are not needed. Abrasion methods including sandblasting, use of abrasives and vapor honing may be required to help remove mill scale, oxide films and certain anti-rust treatments. Chemical cleaning, such as etching, is popular for preparing metals and, where applicable, provide a superior surface for adhesion.
Greases, oils, mold releases, etc. can generally be removed with Environmental Protection Agency (EPA) approved environmentally safe organic solvents or proprietary cleaners. Paints and oxide films are advantageously removed by techniques such as sanding followed by solvent cleaning. For maximum bond strength, follow up with a special surface treatment such as etching for metals.
A simple yet effective test for surface cleanliness is to place a few drops of water on the areas to be bonded. Parts are sufficiently clean if the water spreads to cover the area with a continuous film. If the water beads, a conventional solvent (degreasing) operation will usually prove sufficient for cleaning. Use acetone, isopropanol or similar solvent.
Adhesive primers can be applied to freshly cleaned metal surfaces to avoid recontamination during storage or production delays. They are not necessary if cleaned parts are bonded immediately after cleaning. For specific details on surface preparation, consult Master Bond's technical staff. When using recommended chemicals follow appropriate federal, state and local regulations for safe handling and disposal. Appropriate care is required when carrying out necessary surface preparation procedures.