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Blue plastic and corrosion

RVbySDI

Well Known Member
Has anyone out there tried to decide whether they should leave the blue plastic coating on their aluminum parts while being stored? Well, it is my contention that one should remove the plastic from the aluminum parts as soon as is practical to do so. Now keep in mind, by no means am I suggesting one immediately remove the plastic and store the aluminum sans plastic. However, it is important to recognize that the plastic is not doing very much to prevent corrosion. It does help to prevent inadvertent scratching but preventing corrosion; not so much!

Attached are a few pictures taken today of an RV 14A subpanel. A little history on the attached pictures. We received the fuselage kit the first of April (04-01-2022). The fuselage kit has been kept in an environmentally stable insulated shop with A/C. The A/C is not running constantly but throughout the day as work progresses the A/C has run. The rest of the time the insulated shop does a good job of stabilizing the temp and humidity. None the less, when it came time to add the subpanel to the fuselage build, this is what we discovered once we removed the blue plastic from the subpanel today (07-12-2022).

I did not notice the date of manufacture for this subpanel but most all of the aluminum parts in our fuselage kit have dates of manufacture in 2020. So, this part could have been sitting in the Vans warehouse for a considerable amount of time with the blue plastic on waiting for shipment.

The remedy for the corrosion is partially seen in the fourth picture. I had to thoroughly scuff all of the subpanel with maroon Scotchbrite, paying particular attention to all the rivet holes and edges where the corrosion had started. I do not have a picture of the final subpanel but after the scuffing it was painted.

So, if one is planning to paint a corroded part it is not too bad of a problem to solve. However, if this corrosion were to occur on the inside of a large sheet, say a fuselage skin or wing skin that was not going to be painted, one might have to deal with the corrosion some other way, or perhaps have to replace the piece entirely.

For anyone contemplating the decision as to whether to leave the blue plastic on in hopes of preventing corrosion, contemplate these pictures:
 

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Blue vinyl

Had the same problem with an unassembled empennage. I remove blue vinyl as soon as practical.
When in doubt, remove it and spray SEM all over. You can always remove it and it does a much better job of protecting from corrosion.
 
Vinyl thoughts

I've got an early kit that was made before the advent of blue film, except for a couple of parts that were covered. The parts that had the film on corroded a bit around the edges, whereas the parts that did not have the vinyl film were OK. The vinyl film can be very difficult to remove once it ages and has been exposed to light. I don't think it is worth leaving on during construction, for a plane that is going to be painted, because it will need to be scuffed up anyway during prep.
Corrosion of aluminum parts during storage and construction can be minimised simply by keeping them clean (dust free) and dry.
 
I do remove all the plastic and de-burr the edges as soon as I pull the part off the shelf.

I bought the empennage kit for RV #80566 in December of '98 (IIRC). And, I stored it un touched for 14 years before I began working on it (long story). I did find some minor corrosion under the (then clear) plastic. It all cleaned up just fine with a little scotchbrite. There were a couple of places I sanded just a little with 400 grit sandpaper. But, it really wasn't a big deal at all.
 
Well, I'm confused (as usual)

First, Van's KAI recommends that blue vinyl be removed as soon as practical....for all the aforementioned reasons...but

I always thought the blue vinyl was to help prevent scratching...NOT to prevent corrosion. As a matter of fact, I assumed the blue film would PROMOTE corrosion, not slow it down. Isn't it possible that moisture from temp changes would be trapped (albeit microscopically) between the film and the aluminum, hastening corrosion..?

I had assumed that was one of the reasons Van's recommended it be removed in a timely fashion.

Probably wrong and confused...not the first time, even today.
 
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I suggest to remove the blue

I had corrosion while leaving the blue film.
Then decided to remove all film as soon as practical, never had corrosion afterwards.
As for protection from scratches, it will protect from light rubbing/scratching but not from more important agression if it comes to that.
As a point of data, I scuffed (marroon 3M) the corrosion, then surface primed the affected areas, vertical stab and rudder.
Last month, I started to polish.
I can say that these areas are now as mirror-like as anywhere else.
I also scuffed early on by error a under wing access panel.
Today, it's polished and you can't tell the difference with the skin just besides. Honest !!!
 
Isn't it possible that moisture from temp changes would be trapped (albeit microscopically) between the film and the aluminum, hastening corrosion..?
As you can see in the photos of the panel at the top of the post, the only places where corrosion occurred was around the holes where the aluminum wasn't protected. Under the bulk of the film itself, it's no different than a vinyl wrap... No moisture will get under there because it's sealed around the edges.
 
I say remove it all

I am always in awe of some of the projects I see where everything is polished and shiny. I chose instead to accept the scratches and scuffing and just make sure nothing is too deep as I will paint eventually.

The issue I have seen especially when people remove the blue plastic just around the rivet lines is that the plastic pulls away slightly and then dust collects under that area and moisture and corrosion follows. Mine has that as well, however it was just superficial and priming and scuffing like they would do for paint (way less actually) removes it all. If you are painting I would take Vans advice and remove it all when you can. Others who have build more aircraft may have different advice but if it is going to take you years to build I see no advantage
 
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