Permeability of paint films towards chloride ion

Authors: Carneiro, C.; Oliveira, F.; Nogueira, J.; Mendes, A.

Source: Journal of Coatings Technology and Research, Volume 3, Number 2, April 2006 , pp. 159-162(4)

Publisher: Springer

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Abstract:

An apparatus for determining the permeability of paint films towards chloride ion is described. This set-up implements the time-lag, method and consists of a permeation cell made up of two chambers divided by a supported paint film. The upper chamber contains an aqueous sodium chloride solution and the lower one, water. The permeability is obtained from the conductivity history read at the lower chamber. Osmotic pressure issue is addressed and the 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 the capillary adsorption of water is lower than 0.01 kg/(m²h^0.5) 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 m²/sec for coatings claiming to be corrosion protective.

Keywords: Chloride ion permeability; Time-lag method; PrEN 1504-2; Permeation cell; Concrete corrosion

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s11998-006-0019-0

Affiliations: 1: Email: mendes@fe.up.pt

Publication date: 2006-04-01