It's just lazy writing really. Usually the entire episode's resolution depends on taking some photo from a cell phone, zooming in to a car's rearview mirror that has about 5x5 pixels worth of data, blowing it up to reveal the car behind the car in question, and then reading the VIN number off the front windshield of THAT car. Complete fantasy la-la land.

I'm usually very impressed when a show blows up a photo and nothing usable happens. I remember the first time I saw that on TV - it was an episode of The District. They were using some traffic cam footage to track some car. They had a blurry shot of the car they were looking for, and tried to blow it up to read the license plate. They got an extremely blurry shot of the license plate - nearly useless. But very realistic. The characters were trying to guess what it said - "Is that a D? No, maybe more like an O... or a Q..."

CSI, however, gets Mr. Wizard-grade science wrong. There's no excuse; there's this big thing called the Internet to quickly check facts if they're too lazy to pay an expert to do it. It's like they get some tiny grain of something right (ie. some batteries contain sulphuric acid), and they apply it in a completely inappropriate place (cell phone batteries do not contain sulphuric acid) with completely impossible results (even if it did, it would not eat through steel like that).

A better application, even if still completely impossible? There was a prison riot going on. Power was out, emergency lights were on, and they got trapped in a cell by another prisonor. Why not have one of the emergency lights ripped off the wall earlier and thrown into the cell. Those use lead acid batteries, and he could have taken that apart. There still wouldn't have been enough acid to do anything, but at least they'd be only mostly wrong instead of entirely wrong.