I'm not disputing that the authors of Genesis believed that Noah had access to iron. What I'm saying is that this might be like me telling a story about Jesus using a mobile phone or Nero's love of the Unreal Engine. It would be true in the context of my story, but it would be a glaring anachronism if it wasn't done properly.
For those that have been bothered to do the work (I never have), the Bible can be used to give us a date for the flood at around 2500BC. The discovery of iron smelting/smithing was 1300BC or so according to the link provided earlier. If we were to move the flood a thousand years forward (and say it's a dating issue rather than an anachronism) then a chronology ends up with the Holy Roman Empire still existing today and other such strangeness.
However, when Genesis was meant to have been written (according to tradition, by Moses), was meant to be about 1300BC. Modern historians date a lot of the actual writing to a much later date. It's easy to see why people writing in a world where iron is basically commonplace might think it existed in the time they envisioned the flood events occurred in.
Well, if we're going to start turning to scientific evidence, then we'll just have to throw out the whole flood story: no Noah, no boat, no nothing.
But I think if we are going to ask things in comparing the current ark to the biblical one, it is only fair to base our knowledge of the biblical ark on what is written about it in the Biblesince it never existed in reality anyway. And in doing this, we will also have to look at the biblical record when asking ourselves what technologies Noah had at his disposalsince, again, Noah existed nowhere else but in the story.
When asking questions about a story, I think it is best to turn to the story for answers.
Love your enemies!