The Concept of Historical Aluminium-Pigmented Anticorrosive Armour Paints, for Sustainable Maintenance of Ferrous Heritage

Abstract

ABSTRACT This paper describes the concept of a historical, anticorrosive paint type (armour paint), used on outdoors located ferrous substrates from the early to the mid-20th century. Synthesis from the archive and research reports findings conceptualises a 2 + 2 paint layer system. The system involves red lead linseed oil primer and a top drying oil paint pigmented with micaceous iron oxide and metallic aluminium pigments. This results in excellent barrier properties, high density and elastic paint layers. If moisture reaches the metal and paint interface, the primer acts inhibitive and passivating on the corrosion reactions. The photooxidative deterioration of the paint binder is retarded by the pigment’s ability to reflect light, which affects the lifetime of the paint system. Today, this paint concept is almost forgotten, but associated knowledge of the paint types, paint manufacturing and craft skills could contribute to a sustainable maintenance of ferrous heritage. The authentic concept is, despite its use of a red lead primer, relevant for objects with unique heritage values. The top paints could prolong the lifetime of objects already painted with red lead. A modified concept could initiate development of environmentally beneficial alternatives with VOC-free renewable binders, complex phosphate primers and zinc oxide addition.