The phrase "became inert" is grammatically correct and can be used in written English.
Example: After the chemical reaction, the once reactive substance became inert and no longer posed a danger.
The results of environmental tests carried out on treated sediments showed that polluted sediments became inert.
There were volumes of evidence demonstrating that it was harmless to humans and became inert when it hit the ground.
Switch off the battery, Sturgeon found, and everything stopped: the original lump of iron became inert, and whatever it had lifted toward itself fell off.
(Drug lords use it in their gardens in Kabul). There were volumes of evidence demonstrating that it was harmless to humans and became inert when it hit the ground.
They then become inert and empty.
Shelf life has expired; the ingredients have become inert.
Instead, Lee stays outside, and the movie becomes inert.
But at that point the movie epic dies, and the entire project becomes inert and senseless.
Phrases are so polished that they become inert; narrative dissolves into immaculate moments.
CO2 diffuses from the point of injection to the underground strata and turns into minerals and becomes inert.
This 16-electron complex becomes inert when NIII is a good σ-donor ligand, such as pyridine, 4-picoline or 4-amino-pyridine.
