Calculating time needed to coat an object using the process of electrolysis
The trick you're missing here is that you don't account for how many electrons are needed to reduce $\ce{CrO3}$ to $\ce{Cr}$.
Cr has an oxidation state of 6 in $\ce{CrO3}$, so it takes 6 electrons to reduce every chromium atom.
The full form of Faraday's law is $$\frac{m}{M} = \frac{q}{zF}$$  where $z$ is the number of electrons transferred.
Therefore, you need 6 times as much charge as you initially calculated, which works out to 8550 seconds or 2:22:30.