Fundamental notion

Reminder
In the impact surfaces treatments, the projectile plays the main role. It means it is the tool one must choose and handle properly according to the support nature and the result to obtain.

Choice of the projectile
The choice of the kind of projectile is preponderant and depends on the 7 following parameters:
- its aggressiveness:
The projectile prints on the surface to treat an impression whose mark is directly linked to its shape. Round shapes are more adapted to the aspect treatment and the angular shapes to the surface preparation.
- its mass:
The treatment effects depend on its mass and the projection speed. (see heading parameters) The denser the projectile is, and the higher the speed is, the more its impact on the surface will be important. As soon as the grain hits a part, there is a brutal transformation of its kinetic energy in the form of work (deformation of the surface) and in the form of a new kinetic energy (the rebound).
- its hardness:
It will depend on the nature of the surface to treat and the kind of treatment sought (see heading definitions). The life of the projectile and the projection equipments are directly linked to its choice.
- its resistance:
It is its power to resist to the break-up or the modification of its shapes with the impact. The output of a product depends on the hardness, the ductility and the elasticity of the material it is made of. The reduction of the dimensions of a grain is caused by the abrasion it supports but above all by its breaking-up during the successive impacts. The projectile loses progressively its initial features during the treatments.
- its compatibility:
It takes into account the nature, the thickness, the shape or the quality of the part to treat.
The initial state of the surface to treat plays also a part with regard to the final state which is sought. One must also take into account the compatibility of the product to project with the projection process (see chart 2).
- its granulometry:
The feature defines the calibre of each grain (size and diameter) and thus their number per kilogram projected. It is obtained through sifting and defined according the standard AFNOR NF X 501 and ISO 565. The grains size is important because it has an influence on the output and the quality of the treatment. The bigger the grain is, with an equal speed, the stronger the impact will be, but the smaller the grain is, the higher the number of impacts will be and the better the covering will be (see heading parameters)
- its cost:
It depends on the product quality (homogeneity, hardness, shape and granulometry tolerances). The cost of the treatment is directly linked to the purchase cost of the product and to the consumption of this one.

The charts

In order to help you in the choice, the use or the application of a projectile, 3 charts are available. They will appear when clicking on the corresponding number.

Chart N°1:
Applications of the abrasives and the products to project
It shows first the general compatibility between the products and the projection means.
It shows secondly the compatibility between the product and the nature of the part to treat.
It shows thirdly its aptitude to aggressiveness linked to its hardness and its shape.
It shows then its various applications for some examples of non restrictive treatments.

Chart N°2:
Compatibility of the projection means with the products to project
It shows the compatibility between the projection means and the products to project according to their resistance and their granulometry.

Chart N°3:
Applications of the surfaces treatment in a specific activity field
It shows when and with which quality the surface treatment is applied in a specific activity field.