A question about flash rust

[Johan Maree]

There appears to be a difference in the way cast iron skillets respond to oxygen immediately after they were taken out of a lye bath and scrubbed clean - even skillets from the same foundry.
Some vessels allow for about 3 to 5 minutes (or so) before flash rust starts to form. Others will start to rust while still being cleaned!
That begs the question: Does this indicate impurities in the cast iron, if such a thing exists, or could it be that there is still rust hidden inside the cast iron walls prompting a visit to the electrolysis tank as well?

 

[Doug D.]

Cast iron isn't porous, so there isn't any place for rust to "hide" and then emerge from. Why different pans flash rust to varying degrees under ostensibly similar circumstances is a mystery.

 

[DonnaM]

Cast iron isn't porous, so there isn't any place for rust to "hide" and then emerge from. Why different pans flash rust to varying degrees under ostensibly similar circumstances is a mystery.

How do you keep it at bay long enough to get some type of oil or fat on it?

 

[Doug D.]

The simple answer is, "you don't". When you wipe on your Crisco or other other seasoning oil, it will wipe off as you wipe off the excess oil. Then, the remaining thin layer of oil will form a barrier against further oxidation until you bake the piece to polymerize the oil.

Refer to: https://www.castironcollector.com/seasoning.php#initial

 

[R_Moore]

I was just about to post on this topic. Looking to build an e-tank and was curious how to prevent rust between e-tank and getting oil on. Thanks for the info!

 

[SeanD]

A quick shot of PAM works for me.