How to spot alclad parts

[szicree]

Does anyone know how to tell for sure if an aircraft part is clad? It's quite obvious on RV skins, but I think the forming process dulls the shine on things like ribs making it harder to tell. I've also found that etching removes the shine making it hard to tell. I'm not looking for an answer regarding a specific Vans part, but for a way to tell on any part. Thanks.

[Sam Buchanan]

Originally Posted by szicree

Does anyone know how to tell for sure if an aircraft part is clad? It's quite obvious on RV skins, but I think the forming process dulls the shine on things like ribs making it harder to tell. I've also found that etching removes the shine making it hard to tell. I'm not looking for an answer regarding a specific Vans part, but for a way to tell on any part. Thanks.

I believe it would be safe to assume all aluminum parts that aren't extrusions are alclad.

[flion]

Sam is right, generally bar stock and extrusions (tubing, hex bar, extruded angle, etc.) are not alclad. Everything else (like the formed angle or j-stiffeners) are. Alclad will have plastic covering it, but once you remove the plastic, you have only your memory to go on. On my -6A, I received some ribs (the heavy stock for the tank end ribs, for example) that I thought was not alclad because it was dull and not covered in blue plastic. Turned out it was dull because it was covered in clear plastic, as I found out when I ran a drill through a flange and got plastic wrapped around the bit. I've only seen a few instances of non-blue plastic, though.

[longranger]

Originally Posted by flion

Sam is right, generally bar stock and extrusions (tubing, hex bar, extruded angle, etc.) are not alclad. Everything else (like the formed angle or j-stiffeners) are. Alclad will have plastic covering it, but once you remove the plastic, you have only your memory to go on. On my -6A, I received some ribs (the heavy stock for the tank end ribs, for example) that I thought was not alclad because it was dull and not covered in blue plastic. Turned out it was dull because it was covered in clear plastic, as I found out when I ran a drill through a flange and got plastic wrapped around the bit. I've only seen a few instances of non-blue plastic, though.

Older kits had parts covered in clear plastic, but I don't remember ever seeing a rib covered with anything. IIRC, the ribs are hydroformed in the -0 condition then heat treated to -T4.

[szicree]

I appreciate the responses but I'm still looking for a way to actually tell the difference. I've bought sheets from Spruce many times and always bought the clad stuff so I don't really know what the other stuff even looks like. I guess I was hoping for some way to eyeball a not-so-shiny part and tell if its clad or not.

[Andrew M]

Alumiprep will react with the alloy metals and turn clad parts dark grey on the edges, and unclad part everywhere if left soaking in the solution long enough.
Sometime it is possible to pick out the clad layer visually by die grinding the surface with a sanding disc.
Hope this is what you are after. There are more precise ways to determine metal types using various chemicals, but this should work quick and dirty.

[fixnflyguy]

Steve, If you must know, Alcalad testing is very simple but requires a few chemicals. The sample your testing should be clean and free of oils, ect. A mix of water and some Potassium Nitrate applied with a swab will quickly turn grey or black if no cladding exists. If you intend to use the part after testing, it must me neutralized with Nitric acid, then rinsed with water. All of the parts made from sheet stock on VANS products are clad, however the ribs and formed parts were shaped in the annealed ( "O") condition and heat treated after forming. The heat treat process will slightly dull the bright clad finish. When priming/painting ALclad parts, the most critical areas are the edges and holes, as that is where corrossion will develop first,as the base alloy (2024) is exposed there. All extrusions,tubes,bar stock and castings will be un-clad and require proper priming and painting for corrosion protection. I hope this clears it up for you ! I have spent the last 31 years in the bussiness of heavy aircraft maintenance,modification and overhaul,specializing in metals,structure and corrosion protection..so sorry if I got long winded !