The use of industrial painting is one of the methods for corrosion protection of metals and requires a suitable surface treatment on the metallic substrate for better adhesion between metal and paint film. In cases where the substrate presents low thickness (less than 2 mm), the phosphating pretreatment is widely used, despite of such process generates harmful residues to environment and human health. In this context, the sol-gel method has been highlighted as an easy and a cheap process, and less harmful to the environment. This work shows the development of carbon steel AISI 1005 pre-treatment by sol-gel method using niobium and/or aluminium-containing-resins, synthetized by Pechini method. Electrochemical and performance analysis were carried out in samples coated by the resins, which showed analogous behavior to phosphated systems. The proposed pre-treatment has potential for phosphating process replacement, because the morphology of the deposited layers enhanced the metallic contact surface with the organic coating, increasing its mechanical and polar adhesion. Such observation can justify its better anticorrosive performance, comparing to the untreated substrate.

É amplamente conhecido que a radiação ultravioleta, presente no espectro solar, afeta diretamente as propriedades fisico-químicas dos revestimentos orgânicos, especialmente os obtidos por pintura, em maior ou menor grau, dependendo da natureza química do polímero utilizado em sua composição. Neste trabalho, serão abordados alguns conceitos teóricos referentes à influência da radiação ultravioleta no processo de deterioração de revestimentos orgânicos, bem como serão apresentados os resultados de um estudo específico, cujo objetivo foi avaliar, de forma comparativa, o desempenho de tintas de acabamento frente às radiações UVA e UVB e condensação de umidade. Para tal, foram utilizadas cinco tintas de acabamento (poliuretano alifático [poliéster ortoftálico + poliisocianato alifático], poliuretano acrílico alifático, polisiloxano acrílico, epóxi poliamida e alquídica). A avaliação foi feita com base na variação de brilho, de cor e do grau de pulverulência ou “gizamento” (“chalking”) das películas ao longo da execução dos ensaios. Os resultados obtidos, em termos qualitativos, para os dois tipos de radiação, foram bastante parecidos e, como já era esperado, a radiação UVB, por possuir menor comprimento de onda, portanto maior energia, foi a que causou maior degradação das películas das tintas estudadas, em menor tempo de exposição.

It is well known that the ultraviolet radiation directly affects physical and chemical properties of a large number of materials, specially organic paint coatings, by means of the reduction of its lifetime. In this work, the authors have studied the performance of some topcoat paints (aliphatic polyurethane, acrylic aliphatic polyurethane, acrylic polisiloxane, epoxy, and alkyd) in relation to the effects of the ultraviolet radiation. Some theoretical concepts concerning the influence of ultraviolet radiation on the organic coatings degradation processes are presented, the experimental work is described and the results obtained are shown. The study involved the exposition of the paints to the UVA and UVB radiation, and the evaluation was carried out by the variations of gloss, color and chalking formation. The results obtained from the two sources of radiation were qualitatively similar. As it was expected, the analysis of the overall results shows that the UVB radiation caused greater loss of gloss in a smaller time of exposition, because of its higher level of energy in comparison to the UVA radiation.

A medição de aderência dos revestimentos por pintura pelo método de tração (pull-off), segundo as normas ASTM D 4541 ou ISO 4624, tem sido muito utilizada no campo da proteção anticorrosiva. Trata-se de um método que, além de medir a tensão de ruptura, permite identificar a natureza da falha de aderência. Entretanto, alguns fatores inerentes ao ensaio podem influenciar os resultados. No presente trabalho apresentam-se os resultados de um estudo, realizado de forma conjunta por quatro laboratórios, dentro do qual se avaliou a influência da espessura da chapa de aço (3 mm e 9 mm), bem como do tipo de equipamento, nos valores da tensão de ruptura, em três esquemas de pintura com características físico-químicas diferentes. Concluiu-se que, nas chapas de 3 mm de espessura, independente do tipo de equipamento, os valores são muito inferiores aos obtidos com chapas de 9 mm de espessura. Observou-se ainda que equipamentos diferentes podem conduzir a resultados também bastante diferentes.

The measurement of coatings adherence by the pull-off test, according to the ASTM D 4541 or ISO 4624 standards has been extensively used in the anticorrosive protection assessment. By this methodology, the pull-off strength value is obtained as well as the nature of the failure is evaluated. However, some important inherent factors from the test influence its results. So, in this paper, it is presented the achievements of a study in which four different laboratories worked together in the evaluation of the adherence, by means of the pull-off test, of three coating systems, each one having a particular physical-chemical characteristic. It was investigated the influence of different substrate thickness (3 mm and 9 mm) and of different equipments in the adherence measurement by the pull-off method. It was shown that, regardless the equipment used, when it was used the 3 mm thick substrates the values of the pull-off strength were lower than the cases when the thicker substrates were used. It was also observed that different equipments can lead to very different results.