"small" is kind of a relative term, compared to what ? I think if we knew more- like the number of feet LOA, or displacement or a specific design, well small would take on some tangible shape.
Yes, many designs of small boats can be made of steel, but, like welded aluminum, the skill required grows as the boats get less than 20' LOA (well 18' LOA) and they'd (logically) all be displacement hulls as steel is a bit on the heavy side of small boat building material.
With today's epoxies and hi-tech paints you can control rust and have a nice long life of a small (<18' LOA) boat in steel. Tugs, and work boats of this size are not rare, especially in Holland where there is quite a number of builders who work in smaller steel boats.
Steel is not logical for most planing boats under 40', not for dinghies or row boats, but... there are plenty of designs where steel would make a fine boat in the Glen-L design book. I'm confident there are steel plans available but they may not be the designs you're interested in building? There are a number of small tugs, from work boats to cruisers that were built most beautifully of steel and I believe there are articles here on the web-site reviewing that builder's excellent work?
Hope this helps a little, more info and I could be more directly responsive.