Time
is a fundamental factor when it comes to acting against the corrosion problems of a structure, since the activities that are carried out to recover it depend on this.
by Juan Manuel Álvarez*
Corrosion itself has a direct relationship with time, however, the service time of a structure is determined by the properties with which this structure provides a service under the principle of reliability and safety.
A structure or a structural component can be affected by corrosion, but that does not mean that it necessarily ends its useful life by affecting its properties, what is the interference of the presence and spread of corrosion?
For the purposes of reparability of a structure or a component, a thickness additional to that necessary for the fulfillment of the mechanical work is considered and calculated, which is why it is foreseen that the useful life is determined by the fulfillment of the mechanical work through the properties preserved by the material of the structure or component, thus the corrosion process has begun.
Therefore, the affectation of the materials of a structure or component is foreseen up to a certain parameter in which corrosion is considered repairable, and of course, treatable to be removed or removed without affecting the properties of the material necessary to fulfill its work or use, preserving reliability and safety.
The parameters within which the formation of corrosion products are considered repairable or treatable to be removed or removed, must be considered or taken into account from the outset, particularly for environmental effects, which is why it is a design specification.
The environmental effects to be taken into account for the useful life of a structure or component can be geographical or service. The geographical ones are related to the environmental variables of the region or area, while the service environments are determined by the particular thermodynamic variables, which occur when the structure or component is in service or work.
Variables, techniques and services
Of course, both geographical and service environmental variables must be taken into account simultaneously, the selection of corrosion control techniques will be focused on the most aggressive environment to which the structure or component is exposed, so that the level of protection and the protection time is the greatest, or that it is simply ensured that it complies with the service time that the structure or component requires in terms of use or work.
When the products used in the different corrosion control techniques have a useful or reliable life in the environment less than the useful life of the structure (it is common) that is being protected, monitoring is required for the assessment of the condition of the product being protected, so that the product can be repaired or changed in time or preventively prior to the start of the formation of the products. of corrosion.
Based on the above criteria, the service time of a structure or component is determined by the selection of inspection and monitoring techniques, and by the frequency of inspection for monitoring; thus extending, through the products applied for corrosion control, the protection time without the appearance or beginning of the generation of corrosion.
Service time
To make direct relation to the title of this article, the service time of an affected structure or an affected component is based on the correct procedures of removal and treatment of a corrosion that has already begun, maintaining the minimum dimensions of thickness (for example) for the fulfillment of the mechanical work of the structure or component. Which makes it important to know the remaining thickness after the total removal of corrosion products.
It can be deduced, then, that the useful life of the structures or components is based on a good design, a good selection of materials, a good protection system, good inspections based on the correct selection of the technique and the frequency of inspection, and good techniques and compliance with procedures for removal and treatment of corrosion.
Thus, once again it is demonstrated that the responsibility and results in corrosion control (good or bad results), are those of the people, the corrosionists or the personnel responsible for corrosion control; and at no time in the climate, environment, products, equipment or anything that has intervened or led to the formation and spread of corrosion products, and that after the repair parameters and affect the reliability and safety of the structure or component must be terminated its useful life, either discarding it or recycling it, if feasible and prudent.
Today, taking into account climate changes and analyzing the trends in each of the thermodynamic variables of the environment, products, equipment and procedures must be valued in the best way so that corrosion control personnel can make the changes and adapt with the vision they deserve by responsibly estimating what is necessary to achieve the best performance of a structure or component in the useful life that should always be, as long and as good as possible.
In summary, the above requires the good judgment that must be taken in terms of the objectivity of maintaining the reliability of a structure or component and the security that the structure must provide as a project.
In the next article I will deal with another topic related to the "valuation of corrosion", such as the "Service time of the product, process or corrosion control technique applied to the structure or component", a topic that will aim to provide criteria related to the selection of products related to corrosion control techniques.
As always I wish you a good aging and many successes in your work.
* Juan Manuel Álvarez is a Consulting Member of the technical committees of NACE International, Member of A.S.T.M, of ACICOR (Colombian Association of Corrosion Engineers), of ASCOR (Colombian Association of Corrosion and Protection), of ACOSEND (Colombian Association of Welding and Non-Destructive Testing), of ICONTEC (Colombian Institute of Technical Standards), of the technical committees of END, Welding, Coatings, Fuels and others. He is also a university professor and lecturer. You can write to the e-mail: [email protected]
