Graphite is something of a wonder material for gasket applications. Not much will attack it and it seals over a very wide temperature range. Graphite gasket material is sold mostly in sheet form and has a dark gray, silver-ish color that looks a lot like lead. This is one reason people sometimes assume it’s a metal. The other reason is that graphite conducts electricity, which is something associated with metals.
In this blog we’ll set the record straight.
What You Should Know About Graphite
Graphite is a form of carbon. Carbon atoms can arrange themselves in several ways, which determines its properties. In graphite the atoms are arranged in layers. These can slide over one another, which is what makes graphite slippery, but at the same time, the layers are surprisingly strong.
Carbon is found on the top right side of the periodic table, between boron and nitrogen. This tells us it’s not a metal, because those elements are grouped in the center of the table.
Useful Properties for Gaskets
Graphite is soft and conforms to match uneven surfaces, a key requirement for a gasket material. It also retains its properties over a temperature range from -400°F to 950°F in air (and higher in non-oxidizing atmospheres.)
Another requirement for gaskets is chemical compatibility, and here graphite excels. It resists almost everything except for a few highly oxidizing chemicals.
One weakness of graphite is a tendency to creep under load. This is remedied by mounting it to a stainless steel carrier via little hooks or tangs stamped into the metal. Alternatively, it’s often bonded to stainless foil for increased creep resistance.
Not for Food and Beverage
Unfortunately, graphite is unsuitable for applications where it would come into contact with food or drink. This is because carbon particles can detach and enter into the media. PTFE is usually an acceptable alternative.
Graphite for Gasket Applications
Graphite, particularly when reinforced with stainless steel, makes an excellent gasket material for many applications. Hennig Gasket carries a wide range of types, widths and thicknesses. Contact us to learn more.