J

JVolkober

Well Known Member
I am new builder ? RV9A.. I finally got to the point of riveting my HS. Yesterday I completed the right half and started the left. As I was attaching the ribs to the right side of the forward spar, I noticed white spots and pitting. It looks like corrosion to me, however, I am no expert, more like a rank beginner. From reviewing the corrosion sections of Aircraft Inspection, Repair and Alterations, I believe it is either pitting corrosion, concentration cell corrosion or intergranular corrosion (they said this would be a learning experience). Pictures are attached. If it is, I fear that I will have to scrap the whole HS and s tart over. I figure the cost of purchasing all the parts will run around $450. Then there is the more than a few hours spent getting this far.

The surfaces are all treated an ati-corrosion trantment from Sanchem, Sanchem cc6100. They have been in my shop (garage) for about two weeks since I treated them. The pitting developed over that time.

I am looking for comments and suggestions about this situation and what my options might be.

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Do you have swimming pool chemicals stored in your garage? If so get them out. From your pictures and the short time in storage, you could have a chemical exposure problem.
Mel...DAR
 
JVolkober said:
The surfaces are all treated an ati-corrosion trantment from Sanchem, Sanchem cc6100. They have been in my shop (garage) for about two weeks since I treated them. The pitting developed over that time.
Click to expand...

I'm never used Sanchem products but is it possible you didn't wash off an etching liquid? It looks like you used an acid etch on the aluminum and didn't rense it off. 2 weeks for the pitting to develop seems very quick.

It doesn't look like you need to buy new parts though. I'm sure you could just clean them up with a scotchbrite pad and prime them again. If you have already riveted some parts together, well you get to practice drilling out rivets. I've reskinned a completed 9A HS, it's not too bad.
 
I've been using the Sanchem products on my -9A tail and haven't seen anything like your pictures. Are you sure what you are seeing is pitting? Two things come to mind.

First off, I can't tell from the pictures, but I'm assuming you are using the Sanchem sealer coat. If so, are you then using a heat gun to heat the sealer after it's dried? I've noticed that the sealer I have left over in the cup (never heated) sort of crystallizes and turn whitish color when it dries. If you are not heating it enough (200 degrees) I could perhaps see having this effect.

Secondly, while I didn't get much in the way of directions, I know Sanchem really recommends using distilled water. This may be less likely, but if you're using tap water perhaps this is somehow related.

Overall I haven't had any problems with the Sanchem. Now that I'm finishing up the tail, with the wing kit due to arrive in a couple of weeks, I've been debating changing from the Sanchem to something else. Not sure what, not sure why, just been thinking it over.

Mike Behnke
RV-9A Empennage
Andover, MN
 
Perplexed

I also have been using the Sanchem CC6100 with no problems. I suggested that John contact both Vans AND Sanchem and get their opinions. It is possible the corrosion (if that is what it truly is...) could have been from exposure while in storage at Vans. Kinda hard to believe that after washing, scotchbriting, etching (Part C) and finally chemical conversion coating that there would be any possibility of corroding.

Please keep us informed, John.
 
Sanchem Response

Text of e-mail I wrote to Bret:

Spoke with Sanchem this morning. After describing the situation, the first question I was asked is ?Did you rinse it off?? To which I responded ?Yes, I rinsed the Part C off per instructions but not the A&B mix.? He said that I should rinse the A&B off. :eek: I wiped it dry with paper towels. I noted that the alclad parts ? spars and skins - showed much less pitting than the ribs. He offered that the alclad would have probably limited the additional reaction from not rinsing. I also noted to him that the instructions I received with the treatment said nothing about rinsing after apply the A&B mix. :rolleyes: He didn?t offer to provide me with a partially complete HS.

Question, did you rinse your parts after completing the A&B treatment?

Looks like I will be spending a few hours removing a couple of hundred rivets to get the parts separated so that I can clean them up, retreat them and move forward. The ultimate in rivet removal practice. My wife thinks I?m nuts to continue with the Sanchem. I am a rather stubborn cuss. I?ll try it one more time.
 
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