Surface preparation is an important step for a range of industrial applications, from joining to coating adhesion. Surface preparation methods such as abrasive blasting, degreasing, water jetting, and sanding are all used to remove surface contaminants to provide a clean, dry and properly profiled surface. This type of mechanical preparation can remove adhered mill scale, rust, and existing coatings as well as creating a desired surface profile to aid mechanical bonding. Improving the surface condition through surface preparation can prevent premature coating failure, which is vital for high performance applications. Although some applications do not require surface pre-treatment, it is generally accepted that it is an important step in ensuring the high performance of adhesives and coating systems. Surface preparation is also important for some welding methods, providing a clean and / or textured surfaces to assist joins.
There are a range of different standards related to surface preparation, such as ISO 8501-1, which identifies four rust grades commonly found on uncoated steel surfaces as well as providing grades of visual cleanliness.
Benefits
The benefits associated with surface preparation include:
- Enhanced mechanical performance of joints
- Improved durability in aggressive environments
- Increased component service life
- Ability to bond difficult adherends
Surface Preparation Methods
Surface preparation methods can be mechanical, chemical or energetic. The main types of surface preparation include:
- Cleaning / Degreasing: Removing loose solids, such as with corroded surfaces, can be achieved either manually, such as with a brush, or using an automated method, such as with a blast of air or abrasive blast cleaning
- Surface Roughening: Where light blast cleaning may suffice for some requirements, surface roughening tends towards the use of larger, high pressure abrasive particles, as the size of the abrasive correlates with the effect on the substrate
- Chemical Treatments: This involves immersing a part into an active solution that can etch or dissolve part of an adherend surface or change it so that the treated surface becomes chemically active. An electrochemical reaction can also be included where current is transferred through an electrolyte between an auxiliary electrode and the adherend surface, e.g. anodising, although this introduces several additional factors to be controlled
- Primers: Simpler than many other methods, the application of primers with a brush, spray, or by dipping can chemically alter a surface or protect it