We have already explained here the importance of applying paint to a metal surface, the aim of which is to increase the durability of the structure by creating a physical barrier that separates the environment from the steel.
We have already explained here the importance of applying paint to a metal surface, the aim of which is to increase the durability of the structure by creating a physical barrier that separates the environment from the steel, preventing oxidation and preventing corrosion. Today we will talk about surface treatments and the types of paint and varnish recommended for certain products.
Steel parts must undergo a surface treatment process before being painted. This is a fundamental step in preparing the steel surface for painting, with cleaning and roughening actions for perfect paint adhesion. This step removes foreign materials such as contaminants, oxidation and poorly adhered paint, which can impair paint adhesion.
Nanoceramic treatment
Nanoceramic surface treatment is a process that provides better paint adhesion and greater corrosion protection of the base metal, without the presence of toxic metal ions. This process replaces traditional phosphating baths and does not require special treatment for the water used, and can be carried out at room temperature. The objective of nanoceramic surface treatment is to form a protective film based on zirconium oxide to protect carbon steel, without the need for prior phosphating treatment, high temperatures or the use of deionized water. In environmental terms, it is free of heavy metals and phosphorus, provides a significant reduction in sludge and the bath does not need to be discarded, only the addition of reinforcements.
Types of painting
Some paints, in addition to offering barrier protection, also offer cathodic protection. This type of paint is normally used as a primer, as it contains high levels of anodic metallic pigments in relation to the metal surface to be protected. Zinc-rich paints are an example of this type of finish. The most commonly used paint in this segment is electrostatic powder painting, which fills all necessary recesses, providing very effective barrier protection.
Check out the main advantages of electrostatic powder painting:
– Absence of organic solvents
– Minimal aggression to the environment
– Single layer application, generally does not require primer
– High chemical and mechanical resistance (impact, corrosion, UV, etc.)
– Possibility of obtaining layers of 30 to 500 μm
– Superior and high-level final finish
Powder paint is made up of no liquid components at room temperature. It can be thermoplastic or thermoconvertible. The paints used by Bertolini Sistemas de Armazenagem are thermoconvertible, which are produced by the reaction between the resin and the curing agent after the powder melts. The material polymerizes and forms a component with a high molecular weight, which has optimized physical and chemical properties. The thermoconvertible paints used industrially are mostly polyester, epoxy and hybrid (epoxy-polyester). Learn more about each of them:
Polyester paint
It is recommended for surfaces that are exposed to the elements. Under normal conditions, it presents virtually no problems with yellowing, and has slightly lower chemical resistance compared to the epoxy resin system.
Its most important properties are:
Excellent heat and light stability
Excellent color and shine retention
Excellent resistance to natural weathering (sun rays)
Excellent finishing aspect, in terms of shine and leveling
They also present excellent adhesion and flexibility.
Epoxy Paint
Recommended for painting surfaces that will not be exposed to the weather or sunlight, where high mechanical and chemical resistance is required. Epoxy paints are characterized by the use of only epoxy resin, resulting in coatings with excellent:
Chemical resistance
Adhesion
Hardness
Hybrid paint (epoxy-polyester)
This is the type of paint used by Bertolini, as the properties of the coatings are closely related to the ratio of the amount of polyester and epoxy resin. Bertolini, together with its paint suppliers, seeks the best ratio between polyester and epoxy for the Brazilian market, with the best ratio between the two types of resin.
Colatina Unit Case
Bertolini's pillars of excellence include the quality of its products and respect for the environment. At the Colatina (ES) unit, opened in 2013, all surface treatment systems, painting processes and industrial effluent treatments were designed to achieve excellence in the final finish of the part (high corrosion resistance and excellent paint quality), with total reuse of water. Bath control is carried out strictly, following the supplier's instructions, with periodic monitoring and analysis. With regard to suppliers, Bertolini seeks to approve them only after rigorous quality tests, giving the products a high standard of excellence and ensuring customer satisfaction.
Salt spray tests
Bertolini Sistemas de Armazenagem performs periodic corrosion tests by exposure to salt spray, according to ASTM B 117, NBR 8754 and ASTM D 1654 standards. These performance tests are based on ASTM B117 standard, using a 5% NaCl solution (w/v), with a pH of 6.5 to 7.2 and a temperature of 35 ± 2°C. The edges and holes of the samples are protected with beeswax and an X-shaped incision is made to check for subcutaneous migration. The samples are positioned in the chamber at an angle of between 15° and 30° to the vertical, as recommended by the standard. Subcutaneous migration follows ASTM D1654 standard and is performed immediately after the salt spray tests. Measurements are taken from the incision to the region where the coating has lost adhesion (one side of the scraping) and perpendicular to the incision, with ten measurements being taken along each incision.
