The closest equivalent to Tin Bitz is probably going to be either Molten Bronze (which is the most notorious for being bad paint- this was a first run issue and I don't think it's cleared all store shelves yet) or a mix. Possibly something like Rhulic Gold mixed with Brown Ink.
If you're looking for something like this:
I used a basecoat of Brass Balls with a 4:4:1 Brown Ink/Armor Wash/Umbral Umber wash. You could darken it further by adding a second coat, or possibly by using a darker base color, such as Rhulic Gold.
Incidentally depending on how you want your metals to look, No Quarter 16 had an excellent process:
1. Basecoat with Cold Steel
2. Wash with 2:1 Bloodtracker Brown/Armor Wash
3. Wash with 2:1 Exile Blue/Armor Wash
4. Highlight with Pig Iron
5. Highlight raised areas with Cold Steel
6. Highlight rivets and edges with Quick Silver
The results are an excellent polished steel that really looks impressive
If you want to try something a bit different, you might also like my version of cast iron:
The general idea's not all that different from the earlier suggestion: basecoat with Cold Steel (or any other mid-range grey metal) and then do two washes, Brown Ink and Blue Ink. Unfortunately I can't recall what order- I think Blue then Brown.
But the end result is what you see above. I actually did that back when I had only the Vallejo Game Color line (P3's were not made for another year or two) but it should work regardless. I like it for the fact it reminds me of cast iron pipes and similar things, which seem highly appropriate for the high pressure systems of things like warjacks.