After experiencing blistering on a vintage aluminium engine part, I got in contact with Vapor Blast Solutions to determine what the cause of this was, as it is something I had not seen before.
I wanted to share the response I received for those who have or currently are experiencing blistering on their Aluminium components.
“I see this as a peening issue coupled with contamination at the foundry when the part was made. Most likely the foundry was using all sorts of aluminium for the castings and possibly pouring too cold or not using really good material. If the items were not going to be heat treated, then often the foundry used almost any aluminium for the pour, and I mean any Aluminium.
Peening parts will separate where porosity holes exist and increase the surface size, so the blast that goes down the part surface gets larger and blisters. It can also happen with really expensive titanium parts with thin casting and hollow cavities that are meant to be there… things like jet engine blades.
This happens with fibreglass crash helmets or at least it did at one time. They used plastic abrasive to do the same thing, blister the part surface, so a repair can occur on the unseen hold under the skin of the helmet. Without the repair, the helmet might not pass inspection, so the blister told them where the cavity existed under the gel coat.
I’m going to guess the parts were simply from a small independent foundry… when we were in Paramount we had a small foundry in the complex and they made some impellers… lots of bad parts. Sometimes they used bad sand to pack the mold…
There are lots of reasons for the blistering to occur, but most likely it’s a bad foundry using bad materials for the parts. It happened lots 20-30 years ago.”
Dan Vitaletti – Vapor Blast Solutions