Painting Lead -free jigs

[cadman]

Hawn,
I too like the lower working temp, and the fact that it is lead-free. One last question. I am going to try this one more time. S I have an option of buying 281 bismuth which is 58% bismuth and 42% tin or 281-338 bismuth which is 40 % bismuth and 60% tin. Am I correct in saying that the 281-338 bismuth alloy will paint at a higher temp than its cousin 281? However going to more tin and less bismuth = lighter jigs? Also as far as pouring characteristics, they both should be the same except the one with more tin will be less prone to oxidation. Thanks again and sorry to keep bothering you.

 

[Hawnjigs]

No bother at all. Bi58 Sn42 is the eutectic alloy of the two metals, meaning it is more of a solution whereby the metal will melt completely at 281*F. Any alloy with a close composition like 40-60 will be more of a suspension with part melting at 281* with complete melt at 338*. Thus for powder paint heating, the lower temp is critical because that is when meltdown starts. Kinda like wheel weight melt which becomes sludge before liquid. So, the Bi40 Sn60 will have no PP advantage and will be lighter than 58-42. A higher bismuth alloy like Bi75 Sn25 (3-1) will still exhibit the partial melt 281* characteristic. It requires a much higher bismuth content to buffer the 281* melt tendency of BiSn alloys - I ESTIMATE that Bi90 Sn10 (ruffly 10-1) is the lowest bismuth content necessary to raise the working temp into the 325*-350* range. DISCLAIMER: I don't, so what info I have specific to powder painting is second hand.

Pure lead and bismuth are similar in their tendency to form dark oxide surfaces. My choice for minimum tin added for retarding oxidation is 5% for both metals.

As for pouring, higher bismuth gets slightly, not signifcantly, harder to pour. However adding a little bismuth to pure tin makes it significantly harder to pour.

 

[cadman]

Hawn,
Thank you very much for the bismuth 101 class. Now I finally understand what you are getting at. It's great to know people like you. You have done your homework and know your stuff. It all makes sense now. Thanks again Ted

 

[LedHed]

Great info Keith and very intersting post Ted - thnx guys.

 

[Fatman]

I like it!!!!!!!!