Inspection of degrees of cleaning of steel surfaces

One of the most versatile methods for the protection of steel against corrosion is through the application of a protective coating system. Prior to the application of a coating, the surface must be prepared and cleaned depending on the type of coating to be applied and depending on the user’s expectations regarding the durability of the system in service.

The evaluation of the degrees of cleaning of steel surfaces has a great impact on the quality of service life of a paint system and can significantly affect the cost of a project if the evaluation is not carried out correctly.

The surface cleaning of a steel surface to be protected with a coatings and / or paint system can be done with different methods. The ISO standards and the joint SSPC / NACE standards are the most used in the industry at the international level.

Both standards define the different types of degrees of surface cleaning, as well as different types of initial condition. The requirements for each degree of cleanliness are defined in the written part of the standard, which must be duly interpreted in order to perform the visual evaluation of the surface that has been cleaned. During the evaluation, photo patterns can be used to help interpret the written definition of the degree of cleanliness defined in the standard.

Conflicts in works and projects are often observed due to misinterpretation of the degree of cleanliness required in a specification. Sometimes the compliance of the cleaning of a surface is verified and a decision is made with a simple visual evaluation, without making use of the rule or without correctly interpreting its content. The direct comparison of the cleaning of a surface with a photographic pattern is not enough if the content of the standards is not read and interpreted correctly.

A poor decision on the part of an inspector or quality control technician could affect the quality of the project if a work that does not comply with the requirements of the standard is satisfied.

On the other hand, if a job is rejected or given as nonconforming on a surface that complies with the degree of cleanliness as defined by the standard, the decision could incur very high costs and delays for the project, in addition to the corresponding negative impact for the workers who perform the operation and for the environment that surrounds the work area.

End users and the industry in general must ensure that this type of evaluation is performed and interpreted correctly according to the technical specification of the project. The client must ensure that the cleaning grades are interpreted correctly by the contractors when issuing an offer and executing the work. At the same time, it must ensure that the Inspectors or quality control personnel evaluate and interpret the content of the standards in an adequate manner to avoid that the decisions made in the evaluations affect the quality, production and the cost of a project.

Alejandro Expósito.



Example of a surface to which a dry abrasive cleaning has been carried out. The interpretation of cleaning grades can have a significant impact on the quality and cost of a project.