The authoritative public forum
  for Metal Finishing since 1989
-----

If anodizing is specified, does it mean that the subject is aluminum

If anodizing is specified, does it mean that the subject is almost certainly aluminum.

I have received an enquiry for a casting that has no information at all regarding the material apart from the finish requirements - hard anodizing. Am I to assume that the material is an aluminum die casting?

Thanks

Kevin Stant
Steel Sales - Wrexham, UK
2005

---

It is an excellent bet, virtually a "sure thing", but nonetheless still just a bet.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2005

---

I'm with Ted on this one, but don't discount magnesium or titanium or (heaven forbid) the wrong treatment being called up!

Always best to ask first.

Brian Terry
Aerospace - Yeovil, Somerset, UK
2005

---

When it comes to expensive aerospace parts, much less castings which tend to be pricey anyhow, my money is with Murphy - what ever the worst material it might be, that's the most likely! In that case, one can anodize: beryllium, zinc, magnesium, titanium and aluminium (what we here in the States call AL-U-MIN-I-UM!). I believe that I've got them all listed in reverse order. The fact that the term HARD is used would most likely refer to Ted's "best bet" (likely payback would be a penny-and-a-half on a Euro bet!), but I've heard HARD ANODIZE applied to the Keronite, MagOxid or spark type, HIGH voltage anodic layer applied to magnesium. One other point of contention might be that the part is a "diecast." Typically aerospace aluminum parts would be a sand cast of A356 alloy or the like. Diecasts due to their higher silicon content are difficult to hard anodize to much more than 12 or 15 micrometers and have a soft, powdery outer layer - hardly desirable in the aerospace (or any!) world.

Milt Stevenson, Jr.
Syracuse, New York
2005

---

Milt, to call mentioned by you processes for magnesium like "Hard anodizing" is not exactly correct. Keronite is micro-arc oxidation (MAO) or plasma-liquid coating (PLC). I think MAO is more correct. MagOxide usually is called like spark anodizing or only anodizing.
Of course somebody can be mistaken. However much more chances, that "hard anodizing" is coating for aluminum.

Ilya Ostrovsky
Germany/Israel
2005