Conversion Coating vs Alodine & Iridite - What's the Difference?

Things are still a bit hectic for me.  I'm busy with a new job, and I'm preparing to start up a new class in Aircraft Fuel systems.

I guess I just can't sit still!

I did want to share a short post on a funny experience at work the other day.  Definitely a case of knowing more than I thought I did!

Many of the aircraft mechanics I know about refer to "Alodining" an aluminum part.  It's a common practice to prevent corrosion on components made of non-ferrous materials.

Alodined part.  From Chem Processing, Inc.

You can find some more great pictures of parts having been "Alodined" at this link from Avon Electro.

In my Aircraft Maintenance Studies at Mount San Antonio College, I haven't had much hands on experience with the Alodining process, so it's been relegated to the "I need to read about that later" file, in my mind.

In another life, my design work, I've also worked with the "Chemical Conversion coating" of Aluminum alloys.

I knew that it was a protective coating that prevented aluminum as well.  But there are many processes, and I knew what I needed to know to design parts.

Then one day, it all came together, with a bit of humor at my expense thrown in.

I had to read up on finishes for a totally separate process, and stumbled on to a document that spoke about chemical conversion coating shared by Chem Processing, Inc.

It was short, so I let my curiosity get the best of me, and read the article.

What was one of the first lines in the article?

"Chem Film, sometimes called Alodine or Iridite"

I had to laugh at myself.  All this time, I had been dealing with the same processes, but not even known it.  

Alodining, along with Iridite, are just trade names for chemical conversion!

Alodine image from Aircraft Spruce.

In one paragraph that I stumbled on to via a web search, I had connected the dots, and realized that I had known more than I had.  I was just missing one little link.

Ultimately, I found that I had known far more than I realized.

But what was the other big lesson I learned? Or perhaps, relearned?

Ask questions!  For years.  Yes, years!  I assumed that I knew enough about Alodine and chemicial conversion coating.

And in many ways, I did.  I could design fine with it, I hadn't used it "hands on" ye.

But if I had only asked one question... "What is Alodining".  I could have bridged those gaps a long time ago.

Instead of having adequate knowledge, I would have had knowledge that could have set me a part, if only in a small way.

So that's what I share with you.  Learn from my example, my mistake.

Ask questions.  It is true when it's said the only dumb question is the one you don't ask!

I'll certainly be taking this lesson to heart.

One final note.

If you want to read more about Chemical conviersion coating yourself.  Check out the article I found at Chem Processing, Inc here.

I learned a lot from it!