Two jobs, one product
Ceramic-filled epoxy coatings protect base metal from corrosion and abrasive wear, and they smooth the internal surface of the casing and impeller, which cuts friction losses and can measurably improve hydraulic efficiency.
Good candidates
Casings and impellers with pitting or moderate erosion, where the casting still has structural integrity, coat well and come back close to as-new. It's also faster and cheaper than sourcing a new casting on older or less common models with long lead times.
Where coating alone won't fix it
Cavitation damage is the one that gets misdiagnosed. Coating repairs the pitted surface but does nothing about the root cause, almost always insufficient NPSH at the impeller eye. Recoat without fixing suction conditions and the new coating erodes on the same timeline as the old one. Through-wall erosion is the other hard limit.
Check before committing
● Wall thickness at the worn area, measured, not eyeballed
● Erosion pattern versus cavitation pattern (pitted, sponge-like, near the impeller eye)
● NPSH available versus required at actual operating conditions
● Casting lead time and cost versus coating turnaround
What the smoother surface buys you
Beyond stopping further damage, a properly applied coating leaves a noticeably smoother wetted surface than an as-cast finish, which reduces skin friction losses through the volute and impeller passages. On a pump that's been in service for years, that alone can recover efficiency that gradual surface roughening quietly took away, on top of the corrosion and wear protection the coating is doing.
BOTTOM LINE Coat it when the casting is sound and the damage is surface-level. Go straight to a hydraulic review when the same pump keeps coming back with the same wear.
