Maintenance of Painted Steel-sheet Roofs on Historical Buildings in Sweden

Abstract

This work presents a model and tools with which stakeholders and others involved in the conservation and maintenance process to make informed, evidence-based decisions for the treatment of painted steel-sheet roofs on historical buildings. The aim is to bridge the communication gap between research and practice and to provide useful tools for balancing technical, economic, environmental and historical values. The presented research is based on research and field experiences from practice in Sweden, and focuses on the different stages of building conservation: anamnesis, diagnosis, therapy and control/monitoring. The results are exemplified by systematic descriptions of material characteristics, anticorrosive treatment procedures and quality control checkpoints. A material and method matrix is proposed that can be used in diagnosis, planning and documentation of general procedures, or which can be refined for specific object procedures. It could be used for comparing cases, for suggesting areas of further work or for setting minimum levels for documentation. The matrix can be connected to different quality standards of conservation. It may favour the communication and systematic assessment of working procedures for different substrates, and the further development of best practices.

Multianalytical Assessment of Armour Paints—The Ageing Characteristics of Historic Drying Oil Varnish Paints for Protection of Steel and Iron Surfaces in Sweden

“…Ferrous structures are prone to oxidation and corrosion, and organic coatings have long been employed to protect them. 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.…”

“…The term armour paint, in fact, describes anticorrosive paints that are pigmented with lamellar pigments such as micaceous iron oxide (MIO) and milled leafing metallic aluminum, bound in linseed oil, linseed stand oil and/or tung oil (China wood oil) [1]. AP was traditionally applied in two layers over two layers of primer composed of red lead in linseed oil.…”

“…Armour paints are known for their high adhesion, density, long-lasting elasticity and high weathering resistance due to the formation of an efficient barrier between the substrate and the atmosphere [4][5][6]. Flaky aluminum pigments are categorised as leafing and non-leafing grades, and the former is used in armour paints [1,7]. "Leafing" indicates that the pigment will float to the coating surface (immediately after application) due to surface tension induced by a fatty acid lubricant used in the production of aluminium and lead to a practically continuous metallic film (resembling close-packed fallen leaves), despite the high density of the metallic pigment [1,6].…”

“…Flaky aluminum pigments are categorised as leafing and non-leafing grades, and the former is used in armour paints [1,7]. "Leafing" indicates that the pigment will float to the coating surface (immediately after application) due to surface tension induced by a fatty acid lubricant used in the production of aluminium and lead to a practically continuous metallic film (resembling close-packed fallen leaves), despite the high density of the metallic pigment [1,6]. The thickness of the leafing depends on the pigment and the properties of the binder.…”

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

“…Armour paints display a high elasticity and conformity with the primer and could be a valuable alternative to other paint types. This said, the compatibility of the AP with other underlying paint types must be considered, and sitespecific pre-treatments and application methods devised in order to prevent premature failure of the coating system (Källbom and Almevik 2020). Since 1965, zinc phosphates have been used as pigments in anticorrosive primer systems (Bastos, Ferreira, and Simões 2005).…”