In this blog post, conservator Louise Stewart Beck shared some incredible photographs of corrosion products that seemed to grow from the metal itself. We have found a lot of corrosion products where metal and hard rubber materials meet. In this collection, it happens frequently, and it makes sense to find these two materials so often due to the physical properties of the materials and their uses in regards to electricity.
Let’s start with the metal. Metals are strong materials, allowing the objects to withstand the working environments where they were used. Additionally, metals make great conductors, allowing the electricity to readily flow through the desired path along wires.
While metals are conductors, rubber is an insulator. This means it restricts the flow of electrons and prevents the electricity from transferring to separate entity—like a person—accidentally.
With this in mind, it makes sense that both metals and hard rubber would be found next to each other for the electrical objects to perform their function when first created. The long-term proximity of metal and hard rubber on these objects, unfortunately, also leads to active deterioration of the object. This situation is called inherent vice: The deterioration of physical objects due to the instability of the materials that make up the object.
Group of metal objects with hard rubber carrion on the surface. (Accession number 31.1217.252).
Detail of hard rubber corrosion on surface of the metal. (Accession number 31.1217.252).
When Louise and I encounter the strange corrosion products where hard rubber and metal touch, we end up removing the product of a chemical reaction occurring due to the physical properties of the two materials. If the corrosion product is only removed, it will be back in a few years because the chemical reaction has not been stopped by simply removing the corrosion. Whenever possible, a barrier is placed between the hard rubber and metal to keep them from chemically interacting with one another. Our barrier of choice is Incralac, a clear non-reactive coating. When possible, we apply the coating to the metal after separating it from the hard rubber and allow it to dry. Once dry and reassembled, the barrier layer should prevent the chemical reaction that results in the interesting corrosion growth.
Conservator Louise using a scalpel to mechanically remove the hard rubber corrosion. (Accession Number 31.1217.252).
Conservator Louise submerging metal in Incralac after removing corrosion to form a barrier layer between the metal and the hard rubber to prevent further corrosion. (Accession number 31.1217.252).
Of course, a lot of thought goes in to each treatment for each unique object, making working with this collection both challenging and rewarding. Understanding the ways objects are originally created that may cause or increase deterioration allows us in the Conservation Lab to actively work to slow this deterioration down to ensure the object can be enjoyed by visitors for years to come.
Corrosion removed, waiting for the Incralac to dry. (Accession number 31.1217.252).
Mallory Fellows Bower is the IMLS Conservation Specialist at The Henry Ford.