Graphite heat exchangers are chosen over metal alloys whenever the process fluid would corrode even high-nickel or titanium construction. While metals generally conduct heat better than impervious graphite, that advantage is irrelevant if the metal wall is being consumed by the process fluid, so corrosion resistance takes priority in acid, halogen, and solvent duties.
Where Metal Alloys Struggle
Hydrochloric acid, wet chlorine, and many organic acid streams attack even exotic alloys like Hastelloy or titanium, either through general corrosion or localized pitting. In these services, a metal heat exchanger requires frequent inspection and a shortened design life, which raises long-term maintenance cost even if the initial thermal performance looks favorable.
Why Graphite Resists These Media
Impervious graphite is impregnated with resin to seal its natural porosity, giving it a fully corrosion-resistant wetted surface for most acids and solvents at moderate pressure. Because graphite does not participate in electrochemical corrosion the way metals do, it holds its wall thickness and thermal performance over the full service life.
The Thermal Conductivity Trade-Off
Graphite’s thermal conductivity is lower than copper or steel but still significantly better than most plastics or fluoropolymer linings, so block-type graphite exchangers remain compact and efficient for corrosive duty. The compact block design partly offsets the conductivity difference through high surface area per unit volume.
When to Specify Graphite
If your process fluid is on a metal supplier’s do-not-use list, graphite is usually the next material to evaluate before moving to more expensive ceramics. GreyTec’s graphite heat exchangers are engineered for exactly this gap between metal and silicon carbide, and our engineering and consultancy team can confirm whether graphite fits your specific fluid before you commit to a design.