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Mark Beiser
Jedi Warrior
Offline
I ran into a stopping point on my brake system overhaul, that pesky parts aquisition thing, and decided to clean up my brake drums a bit.
The car lived in and around Pittsburgh, PA for 24 years, so there was QUITE a bit of rust on the drums.
After wire brushing most of the rust off by hand and with power tools, I used some naval jelly to get the remaining rust out of the pores of the cast iron.
After rinsing them off and letting them dry, I started brushing off the white powdery stuff that formed on the surface.
As I was brushing, I noticed that the surface of the cast iron had a dark gunmetal gray to it that looked quite nice. It wasn't uniform in darkness, so I did another treatment with the naval jelly for a few min. After rinsing, drying and brushing the metal again, the color came out very uniform.
It looks almost like the rough surfaces on cast iron cookware.
The machined surfaces didn't have as much of a color change, but they did grey a little.
I realize the color change is due to iron phosphate in the surface of the iron due to the chemical reaction with the acid in the naval jelly.
It is my understanding that the iron phosephate stabalizes the surface of the iron against oxidation. I could be way off on this though. Its been a long time since I studied chemistry, and never studied metalurgy.
The question is, how resistant to oxidation will it be?
I am painting the brake drums on this car, but if the use of naval jelly on cast iron parts has the effect of making them rust resistant, I'll be needing to find a supply of naval jelly in larger containers than what auto parts stores sell.
The car lived in and around Pittsburgh, PA for 24 years, so there was QUITE a bit of rust on the drums.
After wire brushing most of the rust off by hand and with power tools, I used some naval jelly to get the remaining rust out of the pores of the cast iron.
After rinsing them off and letting them dry, I started brushing off the white powdery stuff that formed on the surface.
As I was brushing, I noticed that the surface of the cast iron had a dark gunmetal gray to it that looked quite nice. It wasn't uniform in darkness, so I did another treatment with the naval jelly for a few min. After rinsing, drying and brushing the metal again, the color came out very uniform.
It looks almost like the rough surfaces on cast iron cookware.
The machined surfaces didn't have as much of a color change, but they did grey a little.
I realize the color change is due to iron phosphate in the surface of the iron due to the chemical reaction with the acid in the naval jelly.
It is my understanding that the iron phosephate stabalizes the surface of the iron against oxidation. I could be way off on this though. Its been a long time since I studied chemistry, and never studied metalurgy.
The question is, how resistant to oxidation will it be?
I am painting the brake drums on this car, but if the use of naval jelly on cast iron parts has the effect of making them rust resistant, I'll be needing to find a supply of naval jelly in larger containers than what auto parts stores sell.
