DLC chemical compatibility

[nbog]

Hi all,
one of the potential pump vendors (gear pump) wants to coat
pump gears with DLC coating. Liquid I want to pump may contain up to 40% of nitric acid. Is the coating compatible with this application?
I heard a case of WC coating failing after 100 hrs in a gear pump pumping nitric acid...So WC is out of the game, DLC is being considered.

Thanks

 

[adamant]

Diamond-like carbon is chemically inert in comparison to many other materials. This is especially true for hydrogenated amorphous carbon a-C:H (most commercial DLC), as the carbon "dangling" bonds will be saturated by hydrogen.
Problems will rather arise in case the coating has pin holes, which would mean the acid would come in contact with the gear material despite the coating! DLC is a thin film (a few microns).
The coating manufacturer should apply a coating (DLC or other) which is known for good corrosion protection.
DLC (a-C:H) might do the job, it depends on the coating quality.

 

[nbog]

Thanks adamnat, I hope it will not affect the base material, it is 304 SS.