Definition of quality

Reminder
The constitution of a surface finish is linked to the 4 main features which are: (see heading definitions)
- the appearance, (chemical feature)
- the cleanness, (chemical feature)
- the roughness, (physical feature)
- the hardness, (physical feature)

General points
The appearance is the aspect of a thing considered as identical or different from another thing. It is comparable to standardization but the control is possible only if the standard is stable.
Moreover, the constitution of a standard is valid for one category of products only.
It is thus necessary to evaluate a treatment "quality" or "care degree" through the application of some principles of the visual and tactile test appealing to our faculty of distinguishing the contrasts.
It is impossible to quantify and thus measure an appearance other than by comparison with an ideal state defined arbitrarily. The cleanness is the visual acknowledgement of the more or less important removal of all kind of impurities which can soil the surface of a product in its raw state, after the manufacturing or the use. It allows also updating the possible physical modifications of the structure and at the end of the appropriate treatment, sheltering from the dangers of the surface "story".

Definition
The most practical way to define a thing is to refer to its initial state which, in the case of the cleanness of a surface is the stripping of the product, provided that it does not remain any detectable mark of other material. With reference to this ideal state, a certain number of intermediate phases in the elimination of different impurities is defined arbitrarily.
Nothing being perfect, one admits thus that the maximum cleanness degree to obtain is not 100% but 99%. The criteria recognized for the definition and the control of the care degrees are based only on a visual appreciation of the quality of the surface finish (see heading controls).

Qualities references

The reference standards
There are no general standards for the quality of shot blasting. However there are some recommendations and specific standards which are in the field of the surfaces preparations before painting or anti corrosion coatings.
- the standard AFNOR NF A 35.511 defines the manufacturing conditions and the main features of the shot blasted products before primary painting in the workshop, for the steel-making products laminated under heat.
- the Swedish standard SIS 05 59 00, often quoted, gives only the "rust degrees of the steel surfaces and the care degrees during the preliminary treatment of these surfaces for the anti corrosion paint". It was created in cooperation with the American Society for Testing and Materials (A.S.T.M.) and corresponds to the American specifications of the Steel Structures Painting Council (S.S.P.C.). (see correspondences)

The other references
- the technical specifications of stripping through abrasive projection from the O.H.G.P.I "Office of approval of the guarantees of industrial paint".
- the standard AFNOR NF E 86 800 (1993)
- and the standard ISO 8501-1 (1998)
These are based on visual appreciations and constituted of plates reproducing with colours the standardized degrees of rust and care in life-size. There are four and constitute a characterization admitted as being universal.

Nota:
These comparison plates are valid for steels only, but the notions of care degrees must also be appreciated and specified for the other supports which will be treated through impacts.