I have looked for tubs around here to house rat colonies (1:2) in but can not find anything suitable. So I had an idea to build some wooden boxes and line them with sheet metal flashing which is cheap and should keep the rats from chewing their way to freedom. Cost wise this would work for me as woodworking is my longstanding hobby. What I am wondering is will the alumnium flashing present any risks to the rats?

The main advantage is I can make the boxes to exactly the size I want.
Thanks
Bruce