Influence of PVC on leaching of corrosion inhibitive species
In a new study, researchers present insights into leaching mechanisms by correlating the microstructure of model coatings pigmented with strontium aluminium polyphosphate hydrate (SAPH) to the transport of different species.
It is found that diffusion and transport of active species through the polymeric matrix does not significantly contribute to the leaching kinetics. Thus, leaching starts when inhibitor pigments are in direct contact with the environment via surface-breaking defects in the coating, and continues as long as the cluster of connected inhibitor pigments is in direct contact with the environment, until 3-dimensional connectivity is lost.
Three-dimensional percolation threshold as critical parameter
Therefore, the extent, shape and size of the clusters of connected inhibitor pigments, as well as the solubility and dissolution rates of individual pigments, play important roles in the leaching process. Additionally, the three-dimensional percolation threshold (Pc) for pigment connectivity is proposed as a critical parameter that has significant influence on the leaching rate as well as the barrier properties of corrosion protective coatings.
The study is published in: Progress in Organic Coatings Volume 134, September 2019, Pages 360-372.
