Early ironclads versus armored ships of the line

How did the first ironclads compare with armored conversions of wooden ships of the line?

The conversions were heavy and maintenance-intensive; early ironclads were only slightly better because both were immature transitional designs.

Converted ships of the line became heavy and awkward to handle. Their added iron produced wear, rapid rusting, and difficult maintenance. Purpose-built early ironclads were somewhat better, but not by much. Both types belonged to an experimental transition in which naval architects were learning how iron protection changed an entire hull. The first purpose-built designs should not be mistaken for mature solutions.