by Abel de la Cruz*
Undoubtedly, one of the least addressed operations in terms of its methodology or techniques within the Anticorrosive Treatment Programs of Surfaces with coatings, is the process of acquiring the paint. And it is that this procedure is usually focused through a comparison of costs per square meter of painted surface in the best of cases, since even today, we can appreciate that price comparisons between different supplier alternatives approach it erroneously in terms of costs per gallon of paint.
The acquisition of paint is an important stage, which allows adding value to the profitability of investment in corrosion protection, a central objective discussed in our previous article on "Productivity in coating application" and its effect is in selecting the alternative of the optimal paint system in terms of benefit-cost.
To achieve this objective, an economic evaluation will be carried out through the analysis of painting costs with the different technically approved alternatives to a pre-determined Paint Specification, comparing the Costs of the Economic Life Cycle of Painting with the different alternatives of approved paints.
Economic cycle of painting
The Economic Life Cycle of Painting considers in addition to the cost of the paint and its application at present value, the costs of painting over time, that is, the costs of repairs and future maintenance according to the useful life of the coating. Since, if what is desired is to have the protected area (painted) for a given period of time, the economic calculations must be comprehensive, considering the costs of periodic maintenance, painting, application and technical inspections.
Let's look at the following example of comparing economic life cycle costs of two types of paints in a newly built painting project for a period of six (6) years of protection:
(*) For the example, both calculations have not considered the effect of time on the value of money (monetary updating costs).
Comparing the total costs of six (6) years of protection, including surface preparation, application and quality control inspection work, performing the painting work with Paint B is more economical: US$ 8,000 less than with Paint A.
As a consequence, it would be a mistake to compare only the costs of Paint A ($5,000) versus Painting B ($12,000), without considering the life times and costs of maintenance painting. It would also be a mistake to compare paintings based solely on annual cost, saying that Painting A has a cost of $5,000 for a life span of three (3) years, or $1,666 per year, while Painting B has a cost of $12,000 for a life span of six (6) years or $2,000 per year.
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It is important to mention that in the acquisition operation, the painting itself is not the only object of transaction. That is why the evaluation of the following concepts of value should also be considered:
1.Delivery capacity, in volume and time,
2.Payment terms,
3.Manufacturing quality systems
4.Technical guarantees of good performance or durability.
5.Capacity in the attention and resolution of claims,
6.Pre-sales and post-sales service and technical assistance,
7.Brand recognition and prestige,
8.Experience and record of good performance in previous works,
9.Product quality certifications,
10.Experience in handling coating technology,
11.Research and development capacity for new products,
12.Manufacturing, research and quality control infrastructure,
13.Human resources specialized in anticorrosive treatment of surfaces, etc.
Approval
The economic evaluation described undoubtedly requires knowing as a previous step, the alternatives of "brands" that comply with the Technical Specification of Painting of the Work. That is why the appropriate approval of the coatings proposed by the suppliers must be carried out, on the basis of the paint system with the specified quality.
The homologation of paints consists of the definition of the brands of equivalent paints in performance to the Standard or to the Technical Specification recommended or selected by the engineering. Normally, two or three types of paints from manufacturers are established in order to achieve adequate technical and economic competence.
The Procedure of Homologation of Paints must be carried out by a specialist in corrosion protection with coatings or independent consulting company, through comparative evaluations in three levels of characteristics and / or qualities of the coating and as established by the technical specifications of the work:
a) Evaluation of the physical characteristics or properties of the paint.
b)Evaluation of resistance characteristics of coatings against the medium.
(c)Evaluation of the durability characteristics of coatings against the Medium
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The evaluation of the characteristics or physical properties of the paint fundamentally, do not measure performance, but allows us to know the characteristics and conditions of application, as well as the performance of the paint among other factors. The manufacturer shall provide the technical information in case the Paint Data Sheet does not specify it.
The tests or evaluation tests carried out by the approval equipment can be carried out in specialized laboratories or in the manufacturer's own laboratories under their respective supervision. Among the most common properties we have:
Properties of liquid paint:
The Percentage (%) of Solids by Volume, Weight/Gallon, etc.
Application properties:
Recommended dry and wet film thickness,
Drying times (to the touch, hard, for repainting, for service),
Shelf life of the mixture,
Induction times of the mixture,
Yield
Ease of application with brush, roller, gun, immersion,
Environmental conditions limits and recommended application, etc.
Film appearance properties:
Color, Brightness, covering, smoothness, etc.
The evaluation of the resistance characteristics of the coatings is of great importance to know the behavior of the paints against the environment that surrounds them during their commissioning, however, it does not infer durability characteristics. This information is not normally available in the Paint Data Sheet and needs to be expressly requested from the manufacturers and has the character of an affidavit and therefore of legal responsibility. Among the most common features that are required, there are:
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Resistance characteristics:
Hardness
Abrasion
Adhesion
Flexibility
Impact
Chemical agents (acids, alkalines, hydrocarbons, brines, etc.), Resistance to dry temperature and wet temperature for immersion paints, etc.
Finally, the most important characteristics that must be evaluated by the homologation team due to the direct effect on the frequency of future maintenance and the service life, are the durability characteristics.
The evaluation of the durability characteristics of the coatings against the operating medium, allows us to project the good performance of the paints and even in terms of useful life, that is, the time that elapses from the application of the paint system to the first major maintenance when the coatings are exposed to the aggressive action of the medium, its contaminants and/or the action of industrial products in permanent contact or by splashes: crude oil, fuels, brines, water, acidic and alkaline chemicals, etc.
This information, recorded by some manufacturers allows them to grant guarantees of durability in terms of service life.
The evaluation and prediction of the behavior (Durability) of painting systems are carried out by a variety of experimental techniques, although it is important to mention that in the case of accelerated laboratory tests between several paint systems, the results are comparative and not absolute in terms of service life.
Durability characteristics
Natural exposure tests:
It consists of the exhibition of the paint or painting systems in panels or specimens located in the aggressive environments or media of real operation: Eg. Outdoors, in chemical plants, in immersion, etc.
Despite their high cost and long life, they are today the most appropriate reliability and provide the best precision in anti-corrosion behavior at the time of approval.
Accelerated laboratory tests:
In order to obtain a faster response, there are accelerated corrosion devices in which the coating is subjected to the action of more severe means: Salt Spray Chambers, Condensed Moisture, Sulfur Dioxide, Weathering (combination of humidity and UV rays), etc. Dwell times change depending on the degree of corrosion resistance required, and can commonly vary between 1,000 to 3,000 hours. The results of the behavior of the painting systems are relative and comparatively express the greater or lesser anticorrosive capacity of the systems tested.
Behavior in previous works
In our environment it is the most common way to obtain information on the behavior (durability) of paints in different aggressive conditions. Therefore, it is recommended to carry out a periodic evaluation and a "record" of the painting systems applied in the different works and based on these results and experiences we can recommend or specify paints for new surfaces in similar environmental conditions.
*Manager AmericanConsult Peru. [email protected] http://www.americanconsultperu.com
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