Preparation of the surface before gluing

Surface preparation can be divided into two main methods:
 

Mechanical preparation: the surfaces to be bonded are, in short, grinding / sandblasting, etc. treatments. Depending on the given material and further activities, it is necessary to choose whether such an action is needed at all and how strongly it should affect a given element. It should also be remembered that in the case of, for example, a painted surface, the glue will stick to this layer and if we do not remove it, the gluing will be as strong - as the layer itself, as long as we use the appropriate glue. Sanding the surface will almost always increase the strength of the glued element for a simple reason - we increase the gluing surface; however, there is an exception to this, and it is very important, especially in relation to composites. If grinding can disturb the entirety of the connected element, e.g. a laminate with glass fiber, sanded so much that the fibers will be exposed, the surface in such a place will be strongly weakened and therefore we must avoid such situations, and if there are reasons to sand it, do it in such a way that just slightly roughen the surface or use another glue, eg SA10, which will bond without the need for such preparation, or even matting. On metal and plastic surfaces you can, but do not have to, perform the above treatments, the only condition is if the glued element is previously sandblasted anyway, or we need to remove the top layer, which is easier and faster to remove mechanically than chemically. The only surface that is almost always worth roughening one way or another is rubber.

Chemical preparation: - always recommended before gluing, varnishing, etc. Degreasing is not only washing the surface, but, as the name suggests, removing fats, etc., impeding compounds or even preventing proper gluing and leaving the clean surface free from the above compounds. An important and sometimes confusing aspect is the fact that products such as solvents, gasoline, thinners etc. are NOT degreasers in most cases. They wash off the surface very well, but there is always a micro-layer left after use, which hinders the gluing process, and more. What then to degrease? There are various chemical agents for the appropriate degreasing, some more aggressive, such as acids, or less, such as pure alcohol. Of course, it would be unreasonable to use, for example, spirit (pure non-salicylic) because of the price, but there are two measures that perform this activity best both in terms of cost and quality. Pure acetone and isopropanol, or colloquially speaking: alcohol. By using the two above measures, depending on the material to be joined, we can be sure that we will do it in an appropriate and, importantly, fast, cheap and non-invasive way, thanks to which the entire process will run properly.

 

Metal degreasing: IPA and acetone can be used in most cases; come on corrosive metals, however, the former is recommended.

Degreasing plastics: definitely IPA - less aggressive and will not damage / damage the surface (except for laser cut PMMA - we use a specialized product)

Glass, stone and rubber: both

Composites - laminates: both

Wood - recommended for plastic or for heavy dirt on metals