SPOT TREAT & PAINT - AL SKIN ?

[DCarlton]

When the pros clean, treat and repaint small areas of surface corrosion on AL skin (size of a quarter for example with light bubbling of the paint), do you use a conversion coating after the paint has been removed, or just apply a zinc phosphate primer?  I found this Alodine touch-up pen at Aircraft Spruce but it's expensive.  Wondering what makes sense for smaller areas.  Appreciate your time.  

https://www.aircraftspruce.com/catalog/cspages/touchprep.php?clickkey=11999

[Fly Boomer]

12 minutes ago, DCarlton said:

When the pros clean, treat and repaint small areas of surface corrosion on AL skin (size of a quarter for example with light bubbling of the paint), do you use a conversion coating after the paint has been removed, or just apply a zinc phosphate primer?  I found this Alodine touch-up pen at Aircraft Spruce but it's expensive.  Wondering what makes sense for smaller areas.  Appreciate your time.  

https://www.aircraftspruce.com/catalog/cspages/touchprep.php?clickkey=11999

I have some spots similar to what you describe.  I bought that "pen" that you reference, but I can't yet provide a PIREP.  From what I read, it sounds like the best solution.

[DCarlton]

1 hour ago, Fly Boomer said:

I have some spots similar to what you describe.  I bought that "pen" that you reference, but I can't yet provide a PIREP.  From what I read, it sounds like the best solution.

Interesting that they have two versions of the pen; not evident which one is best.   

https://www.hisco.com/bonderite-alodine-871-bonderite-alodine-1132?utm_term=bonderite pen&utm_campaign=Lead Gen | Henkel | PP&utm_source=adwords&utm_medium=ppc&hsa_acc=8827094775&hsa_cam=15141163613&hsa_grp=136025990384&hsa_ad=558251650463&hsa_src=g&hsa_tgt=kwd-1465637198372&hsa_kw=bonderite pen&hsa_mt=p&hsa_net=adwords&hsa_ver=3&gclid=CjwKCAjwqJSaBhBUEiwAg5W9pzGtV0dSYAwDA0fbUHjUStC5vh3Ev_GwQVqv2aJWcGuYoVVb47v8_BoC1qIQAvD_BwE

BONDERITE M-CR 1132 AERO is a hexavalent chrome chemical conversion coating and BONDERITE M-CR 871 AERO is a trivalent chrome chemical conversion coating. BONDERITE M-CR 1132 AERO leaves an apparent yellow gold coating after application and BONDERITE M-CR 871 AERO leaves a clear iridescent coating after application. Performance of both coatings meets the same corrosion protection and paint adhesion requirements per MIL-DTL-81706B.

[PT20J]

Forget the toxic Alodine and Zinc Chromate.  Use PreKote and an epoxy primer.

 

[A64Pilot]

Yeah we went to prekote as opposed to Cad plating main spars years ago, if something sounds too good to be true?

New owner loved the Engineer who was talked into it, saved lots of money, Engineer said Boeing was using it.

We had troughs that we soaked the spars in, 4340 steel spars, just soaked them for awhile 

Aluminum wise ALL aluminum went through the Alodine tanks, that I don’t think has changed

[McMooney]

36 minutes ago, PT20J said:

Forget the toxic Alodine and Zinc Chromate.  Use PreKote and an epoxy primer.

 

Brings back memories, i used to work for this company

 

[Fly Boomer]

1 hour ago, DCarlton said:

Interesting that they have two versions of the pen; not evident which one is best

Hmmm.  Now I need to do more research.  Not sure which one I ended up with.

[Kelpro999]

For spot repair I’ve been using same old etch/ alodine process applied w/Qtips. Tape off with round foam tape for a soft edge followed by rattle can zinc phosphate yellow. Top coat acrylic urethane for blending. The cheap HF tools airbrush $10 item works remarkably well for this. 
 After chasing spots on my C for two years, I’m in process of a complete. Hope this helps 

[Pinecone]

Funny that people worry about the lead in the fuel and then use a product with hexavalent chromium.

MUCH more nasty.

 

[A64Pilot]

2 hours ago, Pinecone said:

Funny that people worry about the lead in the fuel and then use a product with hexavalent chromium.

MUCH more nasty.

 

It is, but concentration / dosage is also very important

[Pinecone]

Yeah, but Hex chrome is VERY nasty.

I recommend supplied air when working around it where could be airborne.

FYI, my profession is occupational health and safety.

[A64Pilot]

I believe they are talking about one of those paint pens that let out one drop at a time.

At Thrush we had tanks that were I guess 6ft deep and wide and about 30 ft long with a basket and traveling crane to alodine Aluminum en masse that’s been in use since 1965. I think 6 in all, only one with Alodine

 

[Pinecone]

I understand that they are talking about the paint pens.

And it should be controllable.

But hex chrome is NASTY.   But it works well.

[DCarlton]

On 10/13/2022 at 8:30 PM, Kelpro999 said:

For spot repair I’ve been using same old etch/ alodine process applied w/Qtips. Tape off with round foam tape for a soft edge followed by rattle can zinc phosphate yellow. Top coat acrylic urethane for blending. The cheap HF tools airbrush $10 item works remarkably well for this. 
 After chasing spots on my C for two years, I’m in process of a complete. Hope this helps 

Any chance you have a recommendation for a top coat for spots?  Are you using a two part urethane?  I found the one in the attached pic but it's expensive.  Not sure if it's easy to use with one or two small spots either.  Thanks.  

[Marc_B]

@DCarlton That's a 2 part paint that I think works well with proper prep.  Only downside is that it's pricey for a can and it's only good for 24 hours once activated.  For small areas spray into a bag and use a paint brush to fill the areas.

Marc.

[Kelpro999]

3 hours ago, DCarlton said:

Any chance you have a recommendation for a top coat for spots?  Are you using a two part urethane?  I found the one in the attached pic but it's expensive.  Not sure if it's easy to use with one or two small spots either.  Thanks.  

Acrylic urethane (yes two part) works well for spot repairs because it blends, cut/polish unlike enamel type tops. Auto paint supply can match colors at a price but spot repair of corrosion ares usually means a complete is in your near future and blending may not be very important to you. Arresting corrosion should be top priority at this time. I have also used rattle cans of approximate color to “seal” top surface until complete could be done. 

[MikeOH]

Hmm, when it comes to aviation, I don't find 0.043AMU to be expensive

Spray away, I say!

[DCarlton]

20 hours ago, MikeOH said:

Hmm, when it comes to aviation, I don't find 0.043AMU to be expensive

Spray away, I say!

Perhaps just wasteful if you only need to use a little at a time but once opened you have to use all of it before it goes bad.  

[MikeOH]

1 hour ago, DCarlton said:

Perhaps just wasteful if you only need to use a little at a time but once opened you have to use all of it before it goes bad.  

How does that work?  It's a sealed spray can, right?  What's "once opened?"

[Marc_B]

5 minutes ago, MikeOH said:

How does that work?  It's a sealed spray can, right?  What's "once opened?"

@MikeOH there is a button on the bottom of the can that punctures a membrane inside the can when you push it in. Then you can shake to mix the components. 

[MikeOH]

1 minute ago, Marc_B said:

@MikeOH there is a button on the bottom of the can that punctures a membrane inside the can when you push it in. Then you can shake to mix the components. 

Thanks!

So, yeah, wasteful.  But, if I wanted to stop corrosion on a small area...I still consider 0.043AMU to be a good value

[carusoam]

A real CB would figure out how much square area of surface corrosion he can improve with one opened spray can….  
 

Where there is one breakdown of the paint surface… there may be another…

 

My M20C had a paint crack start at the top of the door opening…  About one square inch…

It fixed up really well… not visible to anyone that didn’t know…. A real experiment in paint matching and blending and getting the thickness right…

 

More spots needed attention in the familiar wheel well areas after that…. The A&P gave it the professional attention that it needed…

 

Best regards,

-a-

[Fly Boomer]

On 10/13/2022 at 10:30 PM, Kelpro999 said:

For spot repair I’ve been using same old etch/ alodine process applied w/Qtips. Tape off with round foam tape for a soft edge followed by rattle can zinc phosphate yellow. Top coat acrylic urethane for blending. The cheap HF tools airbrush $10 item works remarkably well for this. 
 After chasing spots on my C for two years, I’m in process of a complete. Hope this helps 

I know this post is a little dated, but I have a number of corrosion spots that need attention, and I wanted to understand better what we can do.  I have one of the small-quantity alodine kits, and I have a specialty paint supplier, but I didn't understand the part about "Tape off with round foam tape for a soft edge".  I understand how using something round helps to avoid a sharp edge, but I can't find any product that could be described as "round foam tape".  I just searched through several hundred products from 3M that are identified as "foam tape", but none seem to fit the "round" criteria.  What product do you use?

[RoundTwo]

24 minutes ago, Fly Boomer said:

I know this post is a little dated, but I have a number of corrosion spots that need attention, and I wanted to understand better what we can do.  I have one of the small-quantity alodine kits, and I have a specialty paint supplier, but I didn't understand the part about "Tape off with round foam tape for a soft edge".  I understand how using something round helps to avoid a sharp edge, but I can't find any product that could be described as "round foam tape".  I just searched through several hundred products from 3M that are identified as "foam tape", but none seem to fit the "round" criteria.  What product do you use?

And as an aside, at what point in a paint job’s lifespan does the paint begin to pop off of the rivet heads? Are rivet heads the canary in the coal mine for aircraft paint?

R2

[glbtrottr]

A card carrying CB would learn to paint his own airplane and buy the supplies to do it- specially when he owns more than one

And get his teachers to donate him several cans of aviation Imron ….


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