I have used wooden dowels with great success over the years for many projects. 5/16 or 3/8 inch (8 to 10mm) diameter in 3/4 boards. I don't know what stock size wood is "Down Under",
It takes a bit of extra work and four bar clamps, but the joints are "blind" (they don't show) and there is no metal to rust. Tightbond II is more than strong enough and you can get a Langstroth size box out of a six (rather than eight) foot board and save money.
If I were to use nails, they would be "6D" Galvanized 2" long, and I would pre-drill the edges to prevent splitting, or I would use deck screws.