Coating Iron: A Reactive and Proactive Solution

Anna Funke, Gyllian Porteous, Flavia Puoti, Johanna Rivera-Diaz, Justin Schwebler, Chris McKenzie, and Claire Achtyl


As the theme of this year’s AIC conference states, conservation can include both reactive and proactive interventions. This paper will closely investigate two case-studies of cast iron cannons that were treated with an epoxy and polyurethane three-part outdoor marine coating commonly used in historic preservation. It will discuss how the same coating system can be used both as a reactive treatment when it stops advancing corrosion as well as a proactive treatment when it prevents future damage. In addition to the detailed discussion of these complex treatments, this paper will investigate the challenges that metals conservation in particular faces around the principle of re-treatability. The first case study discussed in this paper is a cast iron cannon from the revolutionary war that was recovered from the Cooper river in South Carolina in the 1980s. After recovery it was left to dry out. Over the years, large fragments had started to fall off the surface due to chlorides trapped in the iron. A treatment reacting to mistakes made in the past was therefore required. Given that the object is owned by a small county museum, funds for this project were very limited and made full desalination impossible. It was therefore decided to use the afore mentioned coating system as it would eliminate interaction between the iron and oxygen and was therefore the best option in trying to prolong the life of this rapidly corroding object. The second case-study discussed here is the treatment of three civil war era cannons. While these were in very good condition when they were recovered from the PeeDee river, it was discovered half way through the treatment that they would be displayed outside where they would be exposed to the harsh climate of South Carolina as well as roaming visitors. This prompted us to take a much more proactive treatment approach and apply the same heavy coating system, which would be able to protect the underlying material from a harsh environment and prevent future damage. While the coating system described here is significantly more interventive than would usually be advisable for conservation treatments, the nature of these two case-studies required both reactive and proactive approaches in order to ensure the longevity of these cast iron cannons. Furthermore, these treatments presented an interesting opportunity for exchange between conservation and historic preservation. Given that the latter often deals with treatments that must withstand much greater pressure from both the environment as well as human interactions.

2020 | Online | Volume 27