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

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.

Multi-Analytical Assessment of Bodied Drying Oil Varnishes and Their Use as Binders in Armour Paints

“…The solid films were, despite this, expected to contain some inhomogeneities. When the binder is mixed with pigment, the effects of the autophobicity of the air-blown varnish (OH) are less pronounced, as described in previous work [1,2].…”

“…This work aims to investigate the ageing characteristics of binders alone in order to reveal more information about their function as part of armour paints. Armour paints are paint systems that have shown remarkable performance and have lasted outdoors for over 85 years, as exemplified by the Oat Mill in Stockholm [1]. The concept and ageing characteristics of aluminium-pigmented armour paint-a historical, anticorrosive paint type from the early 20th century-entail excellent protection for weather-exposed ferrous substrates [1,2].…”

“…Armour paints are paint systems that have shown remarkable performance and have lasted outdoors for over 85 years, as exemplified by the Oat Mill in Stockholm [1]. The concept and ageing characteristics of aluminium-pigmented armour paint-a historical, anticorrosive paint type from the early 20th century-entail excellent protection for weather-exposed ferrous substrates [1,2]. Armour paints are of particular relevance for historical ferrous objects for which there is a need for sustainable and greener paint systems and a desire to replicate historical practices in applications.…”

Analytical Investigations of XIX–XX Century Paints: The Study of Two Vehicles from the Museum for Communications of Frankfurt

“…Therefore, the identification of an oily medium in a coating may suggest that it was produced before 1950, while the presence of synthetic resins suggested a later dating. Furthermore, alkyd paints almost completely replaced oil paints in the second half of the XX century [4,6,7,11,[13][14][15].…”

“…Zinc white (ZnO) was discovered in the late 1700s; lithopone, a mixture of 70-72 wt% of barium sulfate (BaSO 4 ) and 30-28 wt% of zinc sulfide (ZnS), was discovered in the late 1800s. They were commonly used to replace lead white in the first half of the XX century [4,6,7,9,[14][15][16]18]. In 1918, the first titanium white was produced as a mixture of 30% titanium dioxide (TiO 2 ) and barium sulphate (BaSO 4 ).…”