Abstract
The characteristics of armour paints, historically used to protect ferrous industrial heritage, are explored. Amour paints contain lamellar and highly reflexive pigments of micaceous iron oxide (MIO) and metallic, leafing aluminium, bound in linseed oil and linseed oil–tung oil mixtures, on an inhibitive and soap-forming linseed oil primer (red lead). It is the first study of the binding media used for historical armour paints and investigates the chemical and physical ageing of armour paints using a multianalytical approach. Naturally aged examples are compared to accelerated aged replica armour paint, and to historical paints. The ageing and degradation reactions are assessed by complementary GC–MS and FTIR, together with measurements of wettability, hardness and surface colour. The historical paint formulations include linseed oils and alkyd binders. The results confirm that the leafing effect of aluminium pigments results in only a small concentration of binder at the surface: the paints studied reflect light and form a strong chemical and physical barrier. Linseed oils and tung oil mixtures have been proven to be suitable for the production of armour paints, but the evaluation of ageing and assessment of physical changes will require further investigation.
Highlights
A primer paint remade of red lead bound in linseed oil, with armour paint top coatings, was investigated in two variants and ageing regimes: one with modern low temperature-heated linseed oil varnish, and another based on a high-temperature-bodied linseed–stand oil–tung oil mixture
A number of replica armour paints were made based on historical descriptions, with lamellar and highly reflexive pigments of micaceous iron oxide (MIO) and metallic leafing aluminium, reactive zinc oxide, in linseed oil and linseed oil–tung oil mixtures
F-Al and F-armour paints” (AP) were compared to the historical armour paints and the artificially aged replica armour paints P1 and P2 with a multianalytical approach
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Until the mid-20th century, iron bridges, roofing and railings were regularly painted in situ with drying oil varnish coatings to protect them from atmospheric corrosion [1] These historical paints are believed to provide excellent adhesion to the substrate, high tolerance to existing paint film defects, easy maintenance, high and long-lasting elasticity and weathering resistance. A primer paint remade of red lead bound in linseed oil, with armour paint top coatings, was investigated in two variants and ageing regimes: one with modern low temperature-heated linseed oil varnish (blown oil), and another based on a high-temperature-bodied linseed–stand oil–tung oil mixture (similar to original recipes as reported by [1]). Replica armour paints were characterised by a multianalytical approach to follow changes during curing and using a combination of non-invasive and sampling analyses
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