Calcium Oxide

With what?

How thick?

etc...

etc...

etc...

Paintbrush?

Don't get it wet, Auntie, as the slaking process of quicklime is exothermic and we don't want anyone getting hurt, do we?

"We have fabricated CaO coatings on vanadium metal and various vanadium alloys (V-10Cr, V-1Ti, V-4Cr-

4Ti, and V-5Cr-5Ti), for use in liquid metal blankets of fusion reactors. Initially, by monitoring weight change

as a function of time, oxygen was charged into the vanadium alloys (rectangular sample, 2 x 1 x 0.1 cm) at

710°C by flowing Ar-O2 gas. Oxygen-charged samples were exposed in 2.8 at.% Ca-Li at temperatures of 600

and 700°C for times between 50 and 120 h. The thickness of the in-situ-formed CaO was 13 to 30 μm in the

experimental conditions. Thicker CaO films were formed at higher oxygen contents and 700°C, while thinner

CaO films were formed at lower oxygen contents and 600°C. The data show promise for in-situ formation of

CaO layers on V alloys for the fusion blanket application."

http://www.ipd.anl.gov/anlpubs/2001/11/41220.pdf

Get Tom Sawyer (and friends) to do it.

There is not a single "best" process for such a poorly defined sentence fragment. (I maybe just a little redundant there.) From that fragment I cannot even tell if you wish to coat something with calcium oxide or if you wish to coat something onto calcium oxide. Then there must be at least one criteria or attribute of the coating announced to allow for a selection of "best" to any coating process. A few possible attributes are the following:

• Uniformity of coating
• Outgassing
• Durability
• Ease of removal
• Color
• Cost
• Chemical reactivity

Without knowing which if any of these attributes matter, we can only guess what you are looking for in a coating.