Corrosion-inhibited graphite is what? 1

[kevlar49]

I am starting to see some valve specs with the following description for stem packing: CORROSION-INHIBITED DIE-FORMED FLEXIBLE GRAPHITE WITH ANTI-EXTRUSION RINGS.

What is used as an inhibitor? What services does it inhibit corrosion? Is it suitable for spent/ fresh sulfuric acid service?

 

[ApC2Kp]

kevlar49,

Graphite would have small amount of zinc dust to avoid the galvanic attck of stainless steel valve stem for aqueus or ionic liquid services (cathodic protection of SS).

It might be suitable for ambient temperature sulfuric and spent acid. A better choice especially for hot sulfuric acid service would be PTFE packing.