Alodine question (with picture)

Last night I practiced the alumiprep 33, alodine 1201, akzo primer method on my practice airfoil kit.

Regarding the alodine step: From what I understand, the left edge (where the alodine crept under the masking tape) shows too much alodine conversion [i.e. too much time] because of the dark brown color. However, is there enough conversion on the rest of the panel section?

My thought is that if there is even the slightest tint of gold/brown, then it's okay. I mean, all I'm trying to do here is prep the aluminum so the akzo will stick even better. What do you all think?



Thanks in advance for your help.

-Jim

keywords: azko akzo nobel alumiprep 33 alodine 1201 alimiprep alumiprep33 alodine1201 alumiprep-33 alodine-1201

Yep, looks good to me.
That AKZO, while nasty, is great stuff.

T.

Skin prep

That looks like a lot of my parts. If you are really careful, the Alodine makes an even coat. Immersing the part in a vat works best to achieve that, but is probably completely unnecessary. The AZKO is great stuff, really hard to chip off. Be careful not to use it places that will subsequently get painted. I understand that it is not easy to prep for paint.

Alodine is very nasty stuff. It contains hexavalent chromium, which is a carcinogen (see the Erin Brockovich movie for details). Consider using the Sanchem process (http://www.sanchem.com/safegard_cc.html), which is a conversion coating using a permanganate as opposed to chromate conversion. I started using it part way into my empennage. Seems to work just as well and can be flushed without environmental impact. I have not connection with Sanchem other than as a satisfied customer.

Have fun

Michael Wynn
RV 8 Wings
San Ramon

Cleaning

From what I've noticed so far, how well the alodine takes is dependent entirely on the cleaning process. Sometimes when I've missed a spot, the alodine doesn't take properly to that spot. I use a 45 second dip rather than brush or spray it on (except for the big long bits, of course). Your project looks good.

That's what mine looks like...

Looks great to me.

I agree, dipping in a bath is best for the smaller pieces that will fit. You also use far less Alodine this way.

Tips:
Don't stack stuff in the dip tray / trough. The Alodine needs to circulate around a bit. If you stack stuff, you will see shadows where uncovered areas convert a little more than covered areas. In fact, move stuff around while it's in the bath every thirty seconds or so. IF you dilute according to the directions, I believe three minutes is the submersion time.

You can make a cheap dip tray out of MDF and thick plastic sheeting. Just make the trough according to the largest piece you want to dip and line it. When you're done, pour the remainder into a platic container with a lid. You can save it to use down the road.

Trays

I have a plastic tray that will take smallist bits, and then I had a stainless steel tray that is big enough to take wing ribs. I do one piece at a time, counting 25 seconds then flipping over for another 25 seconds, then water rinse and dry. Both trays have taps in one corner. I usually do the alodyning on a table outside and when I'm done I just place the container under the tap with a funnel, open the tap up and leave it while I do something else. Easy cleanup!!

That alodine job looks good. A few darker spots are not going to hurt the finish. When you do the whole airplane remember to rinse the alodine from the bottom up.

fehdxl said:

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Regarding the alodine step: From what I understand, the left edge (where the alodine crept under the masking tape) shows too much alodine conversion [i.e. too much time] because of the dark brown color. However, is there enough conversion on the rest of the panel section?

My thought is that if there is even the slightest tint of gold/brown, then it's okay. I mean, all I'm trying to do here is prep the aluminum so the akzo will stick even better. What do you all think?
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Thanks in advance for your help.

-Jim
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Click to expand...

Jim
All of the Alodined areas are acceptable. When it gets so dark that it looks like 1970s flocked wallpaper (remember that ugly stuff?), you've overdone it. However, even parts which have been left in to long can be salvaged. Simply submerge the part in rinse water. With a gloved (latex surgical gloves) hand, simply rub off the excess Alodine. Be sure to keep the part completely submerged in the water while doing this.
I've found that the best and simplest way to keep Alodine and primer off an area of skin is to simply leave the plastic on that area, until after the Alodine/prime work is done.
I have a rather lengthy describtion of how I Alodined and primed all my stuff. I've got loads of photos as well. As previously recommended, dipping parts in AlumiPrep/Alodine saves time, materials and gets the best results. Let me know if you'd like any photos or more info off list.
Charlie Kuss

Jim,
Just to be clear, to remove excess Alodine, the part MUST be submerged in rinse water BEFORE the Alodined part dries. Once an Alodined part dries, the only way to clean off the Alodine is to put it back into the AlumiPrep.
Charlie

When I do a whole RV, I mix up a 5 gallon container of alodine (about 2 planes worth). To apply I use a Graco air powered fluid pump and spray away. Takes about 10 minutes. About 2 hours if you include washing with soap and then etching.