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label before prime

1bigdog

Well Known Member
Pardon the dumb question. I'm probably going to professionally alodine the interior parts. I would have sharpied the parts numbers onto each part as I remove the blue plastic but I realized the prep will probably dissolve all that marking.

I was considering stamping the parts which is more than a bit cumbersome. Tagging would be equally cumbersome of course and may not survive either. Is there suggested means to maintain identification of internal parts through the prep and alodine process??

Thanks for your suggestions.


Michael B.
 
Don't stamp the parts - the stamping introduces stress concentrations.

Those tie-on tags work pretty well. Do a search for string tags. They come in different styles.

k2-_41a61152-f315-4e4b-9e45-daa87675549d.v1.jpg


I rattle-can sprayed my parts and Sharpie markings show through. Easy!

Dave
 
You could strategically leave certain holes or combinations of holes either un-drilled or drilled to a smaller size such that parts can only line up or mate one way.

Then after alodine and prior to final assembly, cleco the parts together so the hole patterns match, drill the remaining hole(s) to final size, quick disassemble and deburr, then reassemble and rivet.

Adds a little time but probably not too burdensome.
 
what does "professionally alodined" mean? you spray or dip the part and let it dry. complexity hardly on the order of painting an airplane. much easier/cheaper/faster than trusting someone else to return all your parts undamaged. spend time on the stuff that matters.
 
Labeling

I agree the labels will show through. When you label is the question.
I peal vinyl, clean with laquer thinner to remove any glue residue, scuff a small area where the label will go then use sharpie to mark the part. The labels are very small with a fine tip sharpie. When it's time to prep for primer I don't scuff the label area. Primer prep cleaner doesn't remove it and it shows through the primer. I use SW P60G2 so you may not need to scuff. I also use arrows on labels. Two lines at a right angle with arrow points. One points forward or up depending on the part and location. One points inboard. I also label where two parts will mate so the labels never show. When parts are assembled, no labels are risible. YMMV
 
"professionally alodined"

"professionally alodined" meaning I take it to a plating company with a known reputation for correct disposal methods. The prep is not such a huge problem to neutralize, but the alodine itself is a different storey.

I do agree however the thought of leaving parts or even having to transport them leaves me a bit sick inside. The only good news is the plating company is owned by a family friend.

So basically what I hear so far is that sharpie will show through some primers but I'm not sure I'm hearing it will survive the alumiprep of the alodine process.
The uniquely drilled out holes sounds good.

Cheers.
 
I just ordered a set of numbered metal tags and used safety wire to attach them to the various parts being treated.
 
Michael,
The sharpie will not survive the acid prep.
I know of no better labeling than metal tags.
 
metal tags

Gents, that's perfect. It's what I suspected.

I have a stamping kit from Lee Valley so I'll get some metal tags and wire and get stamping.

Thanks a lot for everyones suggestions.


Michael B.
 
Last edited:
NO black Sharpies

"snipped

So basically what I hear so far is that sharpie will show through some primers but I'm not sure I'm hearing it will survive the alumiprep of the alodine process.
The uniquely drilled out holes sounds good.

Cheers.

I found that depending on the primer, sometimes, the Sharpie will bleed through, so that you can see it. FYI, DO NOT use black Sharpies, as they contain a carbon compound [for pigment], which can cause corrosion down the road. Remember, it's under the primer. Use any other color. I used Sharpies [blue or red], then wiped them off with lacquer thinner and applied the paper tags prior to etch, Alodine and Epoxy priming. After the primer dried, I wrote the ID numbers with a Sharpie and removed the paper tags.
The downside to leaving holes un-drilled, is that you must either deburr the holes later, which removes the Alodine and primer. Or you are riveting parts together with burrs on them. Neither is ideal.

Charlie
 
Are you positive about the black sharpie. Black came with my Cleaveland tool kit. Seems like they would use a different color...
 
Are you positive about the black sharpie. Black came with my Cleaveland tool kit. Seems like they would use a different color...

Jon,
I have no real proof of this. I was warned not to use black Sharpies by several of my A&P friends. I was told that they used a carbon compound to make the black dye. This can cause a galvanic corrosion issue if left on the aluminum over a period of years.
Probably not an issue for "temporary" marking, assuming you will clean the ink off, prior to priming or final assembly. Red or blue Sharpie lines are also much easier to see, if you are using them to line up a rib or bulkhead flange with a pre-punched skin above it.

Charlie
PS About 8 years ago, I contacted the company to try to verify this. They totally stonewalled me. You'd have thought I was asking to see the budget for the NSA or something. :eek:
 
I was also looking for an easy way to label parts that would survive the cleaning and priming process and I came up with something that works well for me. I found that I prefer to prime the parts before dimpling them since it makes it a little easier to prime the parts and dimpling doesn't seem to affect the primer at all. But it's really not a big deal one way or another. So I started dimpling a unique pattern on each rib before priming to identify them through the priming process. Dimple the first hole for the first rib, the sixth hole for the sixth rib. One dimple somewhere else to note left or right side. Pick any pattern you want. If you prefer to dimple before priming, then do the opposite and leave a few undimpled holes in a pattern during the priming process. Works great for me and I don't have to worry about keeping track of parts while I'm cleaning and priming.
 
Jon,
I have no real proof of this. I was warned not to use black Sharpies by several of my A&P friends. I was told that they used a carbon compound to make the black dye. This can cause a galvanic corrosion issue if left on the aluminum over a period of years.
Probably not an issue for "temporary" marking, assuming you will clean the ink off, prior to priming or final assembly. Red or blue Sharpie lines are also much easier to see, if you are using them to line up a rib or bulkhead flange with a pre-punched skin above it.

Charlotte
PS About 8 years ago, I contacted the company to try to verify this. They totally stonewalled me. You'd have thought I was asking to see the budget for the NSA or something. :eek:

Thanks for the info, Charlie. I have recently begun using blue, but have quite a bit of my empennage in black.

As for marking, I lay out all parts on the crate packing paper and write the part # on the paper. I then scuff w/ scotchbrite and Prekote, lay back on paper to dry and then remark before priming. Sharpie then shows through for dimpling and final assembly. Think I'll stick with the blue sharpie from here on out:eek:
 
Sharpie

Nothing I can do about markings in place but looks like I will go blue as well.
I do know Vans mentions using Sharpies but only recommends blue because they last longer. No mention of not using black.
 
sorry to get us back on topic

It seems to me for the purpose (surviving alodine prep process)
the discussion is done.

Either the use of pre-numbered metal tags, or blank tags to be numbered, and engraving on the part itself. As to the later, I was a bit concerned that if stamping is seen potentially creating a stress point why using an engraver (I'm assuming electric pencil to be en engraver) would not likewise create stress. Yes, I can see how the stamping itself will deform the part, but likewise with engraving you are removing material. I very much like the engraving idea. Just peel pack the plastic and scribe the part. Done.

As to the black sparpie, I have read the same thing in several places, so I guess I'll go pick up some fine blue's.

Thanks again. Great suggestions about the tags and electric pencil.

Michael B.
(seems every answer has raised more questions - oy )
 
Just curious

Now that you have all the answers to your question, allow me to drift off just a bit.
What are you hopping to gain by having your aluminum parts professionally alodined?
I certainly am not criticizing your choice but you are aware that you'll be adding hundreds of hours of delay and work to your project.
I can see a slight weight savings over primer...
Not so much on the wings but the fuselage will be another story.
Do tell.
 
alodine timing

Hi Earnst

If the question is about why professional, it's to avoid the handling of compounds that should be disposed of properly and the availability of tanks of sufficient size for all the internal parts we would normally prime.

As to the timing, my intent is to take the internal parts from each subset (empennage for now) and have those parts all done up after drill, debur, dimple, countersink, or at least as much as possible given some parts assembly sequencing precludes their complete preparation. So for the parts that have to have touch up I will use something like an alodine touch up pen. They are expensive but should take care of that problem.

Done this way I can't see much time lost, if any, but maybe I'm being naive. And yes, the weight saving was a factor, not wanting build s spray booth ...

I had not anticipate so much delay, so maybe you could expand on that.

Cheers.


Michael B.
 
The question of why "professional alodining", was answered in an earlier post.
I started out alodining parts and made pretty good progress on parts like wing ribs and such. I soon realized that trying to alodine all parts was not going to be possible in my bathtub size tank.
You may have better luck with professional alodine preparation and facilities.
At the end of the wing build I decided to prime instead and made rapid progress vs. what I had learned in the alodining process.
I also understand the toxicity of alodine and the irreversible damage to the environment when improperly disposed.
The work alone is not so much what will slow you down but delivering and picking up parts is what I think will add a great deal of time to your build.
The empenage is a pretty neat little package but once you are on to larger and longer parts, priming out of a rattle can will look pretty attractive.
Later in the build you'll have a couple of brackets ready to rivet before you can move on and with a quick clean up and primer you are ready to move on in less than 30 minutes.
I hope it works for you, good luck.
 
It seems to me for the purpose (surviving alodine prep process)
the discussion is done.

Either the use of pre-numbered metal tags, or blank tags to be numbered, and engraving on the part itself. As to the later, I was a bit concerned that if stamping is seen potentially creating a stress point why using an engraver (I'm assuming electric pencil to be en engraver) would not likewise create stress. Yes, I can see how the stamping itself will deform the part, but likewise with engraving you are removing material. I very much like the engraving idea. Just peel pack the plastic and scribe the part. Done.

As to the black sparpie, I have read the same thing in several places, so I guess I'll go pick up some fine blue's.

Thanks again. Great suggestions about the tags and electric pencil.

Michael B.
(seems every answer has raised more questions - oy )

The electric pencil does not "engrave", that is, it does not remove metal. If you look at it with a magnifying glass, it is just a series of very small spherical dimples in the metal. The bit in the tool is not sharp, but is rounded, about the size of the ball in a fine-point ballpoint pen.

As for the black ink in sharpies causing corrosion, it must take more than 16 years for that to happen. I marked some RV-4 parts as long ago as 1998, and there's no sign of corrosion. Even if the ink has carbon in it, it will be sealed up under the primer, blocking the moisture required for an electrolyte.
 
the alodine "tub"

Hi Earnst

I appreciate your experience in this. Likewise you are painting the picture of why I wanted it to go professional. I know the plating company owner personally. I'll be meeting with them shortly but in my discussion they have tanks meant for large application. In fact he asked if I wanted to do the whole plane. They are also just 30 minutes from my house. I am MUCH more concerned about leaving the parts out of site. So, depending on how phase 1 goes I may end up doing what you did.

Evinrude makes a zinc chromate rattle can that I used with excellent results on a corvette restoration several years ago. That and one other primer are the backup plan.

Cheers.
 
The electric pencil does not "engrave", that is, it does not remove metal. If you look at it with a magnifying glass, it is just a series of very small spherical dimples in the metal. The bit in the tool is not sharp, but is rounded, about the size of the ball in a fine-point ballpoint pen.

As for the black ink in sharpies causing corrosion, it must take more than 16 years for that to happen. I marked some RV-4 parts as long ago as 1998, and there's no sign of corrosion. Even if the ink has carbon in it, it will be sealed up under the primer, blocking the moisture required for an electrolyte.

Miles, thanks for the clarification.
 
Update?

I have been using little numbered tags that I made to identify parts during the coating process. Occasionally they will come loose in handling (and I only have so many of these) and I'd like to try another way.

This thread, old as it is, and a couple of others, reference Van's Aircraft's use of vibrating peening markers and supposed approval of such in the construction manual, but the newer versions of the manual make no mention whatsoever of this.

My spars and center section were marked by the factory with this kind of device, but they don't seem to endorse it for our use anymore. Is there a reason for this?

I sure would like an easier marking method than these little tags...and Sharpie's not an option for me because the solvent wipe completely removes those markings for me.
 
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