Acid resistant coating?

you need to add some details...

which acid?

what abrasive particles?  

what is the equipment?

what are the operating conditions?

etc

There are epoxy resins that you can use but they will abrade just the same.  I have a true story I could tell you about acid treatment of soil slurries as part of a soil-wash treatment plant and failure of the tanks because of abrasion. there is no "permanent" yet cost-effective solution of which I am aware.  There are only short-term measures that you will have to periodically inspect and repair as needed.

A flow of abrasive material? nothing will resist that for long. Depends of course on how abrasive and how fast, but even steel would wear away in time. 

Some sort of Teflon coating may be the best bet.

maybe cerakote ...its expensive though if you have a large area it probably not practical ..