Permeability of Paint Films towards Chloride Ion

Abstract

Art apparatus for determining tire permeability of paint films towards chloride ion is described. This set-lip implements tire time-lag method and consists of a permeation cell made tip of two chambers divided by a supported paint film. The upper chamber contains air aqueous sodium chloride solution and tire lower one, water. The permeability is obtained front the conductivity history read at tire lower chamber. Osmotic pressure issue is addressed and tire reproducibility of the results reported. The time-lag method is not described in any standard. The requirement concerning "surface protection systems for concrete" for chloride ion permeability is not quantified in prEN 1504-2. The standard establishes that this requirement is "subject to national standards and national regulations" but when tire capillary adsorption of water is lower than 0.01 kg(m(2)h(05)) the diffusion of chloride ion is not to be expected. Some experimental results prove this is not correct and, in Portugal, the National Laboratory of Civil Engineering (LNEC) has proposed a threshold permeability value of 10(-14) m(2)/sec for coatings claiming to be corrosion protective.