Property controls

Fundamental notion
Controls allow making sure that the different conditions required for the good realization of a treatment are respected, in order to obtain in the end a result in accordance with the aim decided first. They have to be applied to different phases, on a rigorous way, in order to make sure of the final quality of the product.

Before the treatment:
1) Check the compatibility of the projectile (abrasive) with the one of the support (part) as well as the compatibility of the projection process with the treatment sought. (see heading comparisons)
2) Check that the part to treat is free from any grease or oil:
- through the test of the pure "water film" that the surfaces do not keep (moistening impossible).
- through the test with "copper sulphate" which does not settle on a greasy surface.
- through the test of "ultraviolet fluorescence". It brings out the greasy marks under the ultraviolet light.
3) Check that the part to treat is free from dampness.
4) Compare the initial state of the contaminated surface with the standardized reference plates.

After the treatment:
Control the property state, the absence of calamine, rust or any other contaminated agents:
1) through the "visual" method, based on the comparison of the result obtained with regard to standard plates placed over 4 care degrees. (see reference plates)
This comparison, which brings in the personal interpretation of the controller and might generate litigations because of its subjective nature, can be replaced by:
2) the "scalometric" method which consists in picking up on an adhesive band, applied first on a prepared surface, some surface particles whose percentage can be interpreted by a photoelectric cell.
3) the "measure of reflected light" method described in the English standard BS 4332 (1967).

Conclusion
Property is the feature of a surface treatment the most difficult to measure because it refers to a perfect state impossible to obtain. Consequently, one will take as a reference state the one which allows ensuring the required conditions for the obtaining of the final quality wished.

Roughness controls

Introduction
On a general way, the roughness control is sufficient through the "visual" and "tactile" comparison, except in the case of very high precision manufacturing or the mass production. In the impacts treatment area, it is often a question of evaluating only, and therefore situate in reasonable limits, a roughness "appearance". Knowing that it is difficult to check with an absolute certainty that the roughness obtained after the treatment is the one we would need ideally.

Visual-Tactile control:
Roughness is estimated through a comparison with standard plaques. The most widespread in France are the ones of the "Weapons Central Laboratory" and the "Atomic Energy Commission", called "Rugotest". They reproduce, according to the standard NF E 05 051, 18 surface states representing:
2 types of shapes obtained:
- A - through spherical shots
- B - through angular shots
in treatments:
- a - through coarse grains
- b - through fine grains
Each surface state represented has its correspondence in Ra measure (average roughness). If at the time of the control, the relief effect is disrupted by the presence of a foreign coloration, either external or due to the support, the touch can replace sight in order to compare.

Controls through measures:
This category of controls puts together the processes which, through a direct or an indirect measure, determine the characteristic parameters of the profile of a roughness. These controls, requiring sophisticated means for some of them, are usually made out of the site:
- through a sensor with a diamond point, connected to an inductive sensor which amplifies and records the signals relative to moving of the sensor on the controlled surface. These appliances, commonly called "Rugosimetres", indicate one or several profile criteria, through a direct reading.
- through a laser beam, process similar to the previous one, but in which the sensor is replaced by a means without any mechanical contact with the surface. Therefore there is no risk of marking. The three-dimensional analysis is obtained through a series of micro moving.
- through interferential microscopy, for which the deviation caused by roughness is measured, on the reflection of a light with a wavelength known, by a lighted surface. This process applies only to the surfaces having a high reflective power.
The features of the various controls appliances are not always identical. Therefore, in order to compare and interpret several results, it is essential to use always the same appliance.