Sanchem vs Alodine

I'm getting ready to pound my first rivet, and like most everyone did when they started, I'm trying to resolve the primer / prep question. I found several messages about an alternative to Alodine called Sanchem. At least a couple of folks were testing it early this year, but I've not found any follow-up comments as to how well it actually worked.

I'm considering using just a conversion coating in those areas where there will be no wear. I intend to use either a wash primer (without convewrsion coating), or akzo (or similar) over a conversion coating on the non-skin pieces subject to wear only.

Any help would be appreciated.

Terry Frazier
7A QB, Tail, rivet #1

for your consideration ppg aerospace, manufacture excellent airframe primers, for alltypes of aircraft. if there are area's you do not want to prime, look at products from zip chem aviation. zip chem makes arrange of corrosion inhibitors, cor-ban 35, is a good product offering 2000 hrs salt spray protection. this is a spray and forget system, much safer to use than alodine. have a look at their web site.
don [email protected]

Sanchem First Try

I broke out the Sanchem materials for the first time today. I've chosen the Sanchem 6100 conversion coating system for all substructure parts rather than Alodine because of the simple disposal and handling requirements. Alodine has chromium in it, and presents a real problem for proper disposal. I also plan to coat the substructure and mating parts of the skins with Sanchem Sealer #2. To provide a more durable surface to externally exposed substructure (such as the rear spar), I bought Ankzo primer from Spruce. It's a two part epoxy that is supposed to be very durable plus it's impervious to solvents, etc. Hope the grandkids are interested in a corrosion free airplane someday...

So today, I started to apply the conversion coating to the HS substructure pieces. Quite a job to get an even looking coating. So far, the keys to good results seem to be as follows:

1. Scrub the parts down really well with the Part C prep fluid. It's mildly acidic, so I used nitrile gloves. I chose 3M fine pads which take more elbow grease, but leave a better finish than the medium grit.

2. Let the Part C set a little while on the parts. I even brushed on a little extra for good acidic action.

3. Rinse the parts well with distilled water. It seems that tap water leaves deposits that affect the conversion coating. Just pouring water over the parts is not enough. It's better to rub them a little with the gloved hand to get all Part C off.

4. Have a mixture of 1 part of Part A and 1 part of Part B ready in a small container. Immediately brush on with a disposable brush and let it do it's work. It seems that continuing to brush on additional part A/B whill the conversion process is working helps. Letting the parts set for even a few minutes after rinsing off the part C seems to result in a less consistant finish. Use compressed air to dry a part and put on the Part A/B mixture right away.

5. Let it set for a couple minutes and rinse with tap water.

I still get a blothchy finish sometimes, but the coating seems to cover the whole part well. I talked to the Sanchem folks about the color to expect. They said non-alclad parts will be close to the color of the gold dollar coin you get from the post office (Sakajawea I think). Alclad parts will be not such a deep gold color, but the conversion is still complete.

Lots of work!!!