dip soldering, prevent oxidation ?

By forming a sticky mess?

The oil fills the pores in the cast iron and polymerizes under heat, turning into an 18th century version of Teflon. If not done properly, it can make the pan sticky to the touch.

Searching for Dross-X, I found an outfit that has a powder for this. (Powders are cheaper to ship than liquid hazmat stuff!)

Anyway, I ordered a pound of it, it still cost almost as much to ship as the stuff itself. I'll report back next time I do a batch of these boards.

Jon

Not any: only unsaturated fats.

Some clarification (ha?):

- Oils are either lightweight saturated fats, or unsaturated fats of longer lengths. (Unsaturated double bonds lead to kinks in the molecules, which keep them from freezing.) Oil is simply fat that's liquid at room temperature.

- Fats are triglycerides. (Oils and fats are not free fatty acids.)

- Fatty acids (and glycerin) are produced by decomposition, metabolism or chemical processing (steam separation?) of fats.

Polymerization happens when unsaturated fats bond together. "Varnish" happens when polyunsaturated fats form huge networks (because each molecule can stick to more than one, which can stick to..).

Polymerization is driven by free radicals.

Oxidation leads to epoxides and peroxides, and free radicals. Oxidized fats (and fatty acids) smell, well, rancid.

Steam can hydrate double bonds to form secondary alcohols, and hydrate the fatty acid esters, resulting in lower glycerides and free fatty acids.

Further oxidation can break up the molecules. This is highly likely at reactive sites -- points where there's already some oxygen or whatever stuck on. (The acid tail can break off (decarboxylation), leaving a shorter alcohol; alcohols can be oxidized to aldehydes; and so on.)

Any kind of reaction is highly unlikely at saturated sites. Which is why petroleum products are so stable.

On extended cooking, eventually, the increasingly reactive and rancid soup autocatalyzes itself into brown muck. At least, with most common oils, like canola, olive and peanut.

(By the way, heat also leads to isomerization: the double bonds get twisted around, forming a bend rather than a kink in the molecule. These trans fats aren't well metabolized by the body.)

Now, most natural fats and oils contain a lot of monounsaturated fats (everything from lard to olive oil), so "almost all cooking oils" is probably fair, but I wouldn't say all.

So, it follows: if you want a very heat-stable oil (or fat), you need a saturated fat. Coconut oil is a good example, being some 90% saturated. But it's made of shorter molecules, too, so its smoke point isn't very good.

(In conclusion, food products are probably not what you want for soldering. But you probably guessed that already...)

Tim

Yup! Use a high-polyunsaturated fat: they're prone to forming varnish. Peanut, corn, soybean and especially flaxseed oils are particularly good. Wipe it down, stick it in the oven and bake on a coat. You'll be left with a rubbery, rancid coating.

The rancidity should probably be leached out by wiping it down (then letting it sit) a few times with clean oil. Preferably a high-saturated one like coconut or shortening.

Tim

Some of your definitions above aren't accurate and aren't even self consistent.

Coconut oil is not one oil, it is a mixture. Pure oils are rather expensive.

Your conclusion does not follow from the facts.

On Thu, 7 Apr 2016 16:54:50 -0400, rickman Gave us:

Unfractionated coconut oil is full of long chain triglycerides.

Fractionated coconut oil is easy to get. One version is called "Cap-Tri" (caprylic triglyceride). Body builders use it to add calories to their diet without retaining the added calories as fat.