Visualising under-coating corrosion before visible damage
Recently, scientists developed a new method for visualising under-coating corrosion utilising pH indicators before visible damage.
The method detects corrosion through local pH gradients which are visualised by pH indicators. pH gradients are induced in a setup similar to the one popularized by Devanathan. On the uncoated back side of the metal, the sample is cathodically polarised, generating hydrogen gas through electrolysis.
Visualisation of local corrosion
The hydrogen generated, diffuses through the metal sample and oxidises on the anodically polarised painted side wherever the coating develops a defect causing a decrease in the local pH. The local pH is then used in imaging the location of defects through the use of a pH indicator, before any visible corrosion damage occurs on the coated metal sample.
The study is published in: Progress in Organic Coatings Volume 122, September 2018, Pages 72-78
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