The influence of the method of application of the paint on the corrosion of the substrate as assessed by ASTM and electrochemical methods

P.R. SERÉ; D.M. SANTÁGATA; C.I. ELSNER; A.R. DI SARLI

SURFACE COATINGS INTERNATIONAL

OIL & COLOUR CHEMISTS ASSOC

Año: 1998 vol. 81 p. 128 - 134

1356-0751

Paints have been used for many years to protect steel against corrosion. The effectiveness of the coating depends upon many factors, some provided relatively little protection even under rather exposure conditions. Other will provide complete protection for many years even under severe conditions. Funke et al found that an important factor which previously had not been sufficiently considered was the adhesion of the coating to the steel in the presence of water. Therefore, if the wet adhesion is poor, corrosion protection will be poor in any case, however, if the wet adhesion is good, a low rate of water and oxygen permeation may delay the loss of adhesion and so, for many practical purposes, an adequate corrosion protection level would be reached. A paint fulfills its function only when applied to the substrate. There are a number of ways of accomplished this, and often the type of paint determines the most appropriate methods. Besides, efficient application is a critical point of painting operation. The proper use of the application method utilized to apply the paint or coating, can have a definite effect on the time required, the appearance of the finished job, the performance of the applied product and the total cost of the job. With regard to the performance of the applied coating the application methods can have marked effect, especially when the coating is subsequently exposed to adverse environments. The objective of the present work was to begin the study by using four (brushing, roller coating, spraying and spinning) methods of application of a commercial alkyd of paint on carbon steel. The painted electrodes, exposed to NaCl solutions, were assessed with respect to water and oxygen permeability as well as impedance and corrosion potential as a function of immersion time. Besides, pull-off and tape adhesion tests, as well as salt spray cabinet procedures, were also carried out.