To paint or not to paint

[gobrien]

Rookie question of the day:

It looks like the interior of 80V was primed at some point but it's wearing quite thin. She is bone dry - no damp, no grease or oil except right down at the tail (which I will be cleaning out) so it seems the perfect time to paint the interior. However, my A&P suggested instead go with "buckets of ACF-50" which looks like fantastic stuff: https://www.youtube.com/watch?v=GdGtorJuE50.

Given the state it is in would you go to the effort of painting (or at least prime) or leave it alone and go with the ACF-50?

Thanks,

Gareth.

[hilltop170]

Gareth-
I have used both ACF-50 and CorrosionX for years and feel very strongly that either would be preferred to priming the interior of the tailcone. Corrosion back there appears to not be a problem on your plane so a good dose of corrosion inhibitor should be more than adequate in your case. The wing interiors should be treated as well. You can treat it yourself very easily.

One of the drawbacks of ACF-50 or CorrosionX is if you apply sufficiently to do a good job, there will be weeping thru the seam areas that will migrate to the exterior of the plane. That is also a good thing as it indicates the treatment is effective and that is where corrosion can hide and would not otherwise be treated with interior priming.

The fluids will creep around corners and down into crevices you can’t see even if it is not sprayed directly into those hidden areas. Primer won’t do that. Also ACF-50 and CorrosionX will passivate existing corrosion by seeping between the base metal and electrolyte/corrosion oxides isolating one from the other. Primer will only coat over existing corrosion that is not completely removed allowing the corrosion to continue.

Another drawback is if you are planning on painting the exterior of the plane you should not treat with corrosion inhibitor fluids for a few years before painting as it will inhibit paint adhesion along the seams where the fluids weep out. So, in that case, paint the plane first then treat with corrosion inhibitor after the paint has cured properly.

Hope this helps.

[170C]

I have treated my aircraft twice in the past 4 yrs with Corrosion X and yes, it does weep out of places you would never expect, but that is apparently a good thing. My IA said I didn't need to spend the cost of Corrosion X (approx $100/gallon) or ACF-50 because boiled linseed oil would provide the same protection at a much lower cost and that it adheres to the metal better that Corrosion X or ACF-50. Because I have access to the application unit and Corrosion X I haven't tried the linseed oil, but am curious if others have any knowledge of it.

[eskflyer]

Get a new IA. Boiled linseed oil is for tube and fabric inside tubes, yes it creeps. Use acf50 or corrosion x on aluminum spamcan's. Corrosion x is better in my opinion. But we all know what opinions are like.

Corrosioned x'd my new bird N170AK

Crash aka JP.

[GAHorn]

Linseed oil does not penetrate as well as ACF50 or Corrosion-X unless you “cut” it with a solvent like WD40 or Stoddard solvent. However, spraying WD40 and solvents with pressurized air delivery systems creates a potential safety problem due to flammability. Linseed oil is usually used for iron and steel although it’s sealing characteristics might work well with aluminum. (Raw linseed oil will take forever to dry, boiled linseed oil will dry in a week or so. I think of it as similar to the Boeshield product that dries to a waxy-film. It is the dried product that seals against oxygen to prevent corrosion. The ACF50/Corrosion-X products remain fluid for years and soak into crevices/crannys which is why it “weeps”.)
I have to wonder if it (linseed) will affect control system cables/pulleys and avionics/electrical wiring/connections as favorably as ACF50/Corrosion-X (both of which are approved for the purpose.)
I’d have to suggest that since you are trying to protect an expensive aluminum airplane that you spend the money on the proven products of ACF50/Corrosion-X. (I’d lean toward the Corrosion-X as it was developed as a safer product.)

[170C]

While I think my IA has good intentions and has a vast background in both general aviation as well as airline maintenance, the GA customers I know that use this individual continue to use Corrosion X in our aircraft. Just loaned the application equipment and fluid to another aircraft owner this week. Thanks for your input George.

[gobrien]

Thanks all for the various contributions. I have looked at CorrosionX and it is right about twice the price of ACF-50 over here. Likely because ACF-50 has made its way into the motorcycle industry and is quite widely available.

I'm going to prime and paint the visible areas inside the cabin; I'm not doing the exterior for a few years. Once that's cured I will pump up the high-tech ACF-50 applicator!

[GAHorn]

Gobrien... Just looking at your pics it appears what you are referring to as “primer” might actually be a zinc-chromate type product...which is very common for aluminum aircraft anti-corrosion purposes. If so, you might be advised that it is not necessary to heavily “coat” or saturate an area with it as even lightly painted/primered areas of zinc chromate are very effective at fighting corrosion. In fact, a heavy coating of the stuff mostly just adds unnecessary weight.
The dry and non-corroded appearance of your fuselage bears witness to it’s effectiveness, and you might consider yourself fortunate in that regard and avoid further treatment completely unless there are “spots” which you feel deserve extra attention. IMO

[hilltop170]

I have no way to confirm this but I think most airplanes left Cessna with no corrosion protection/zinc chromate primer whatsoever. The "Alclad" skin was supposed to be corrosion resistant. There was black sound proofing sprayed randomly in the cabin roof and aft fuselage of some planes, which is almost impossible to remove today, but I do not think it was intended to be corrosion protection. Float planes were the only ones that I know of that were treated at the factory. It might have been a factory option for non-floatplanes.

[ghostflyer]

Water will lay between the layers of sheet aluminium, under rivet heads or lap joints and form beautiful little cells that start the corrosion process off. Washing your aircraft with WD-40 in the water is very good as it helps this water displacement process. Spraying it liberally in the interior lubricates cables and pulleys and stops corrosion on bolts and nuts and doesn’t allow ice to form in the joins . Plus it smells good, I heard from a source that “someone” uses it as a cologne . So that’s how good it is .
Realistically myself I use corrX and Boeing shield due to the aircraft living about 100 feet from the ocean .

[GAHorn]

I have no way to confirm this but I think most airplanes left Cessna with no corrosion protection/zinc chromate primer whatsoever. The "Alclad" skin was supposed to be corrosion resistant. There was black sound proofing sprayed randomly in the cabin roof and aft fuselage of some planes, which is almost impossible to remove today, but I do not think it was intended to be corrosion protection. Float planes were the only ones that I know of that were treated at the factory. It might have been a factory option for non-floatplanes.

The seaplane specification included interior primer treatment as did the “agricultural” specification... even if the full equipment were not installed. (Believe it or not that was one of the options back then, ...also a camera-kit, ambulance kit, etc etc.)

[n2582d]

Thanks all for the various contributions. I have looked at CorrosionX and it is right about twice the price of ACF-50 over here. Likely because ACF-50 has made its way into the motorcycle industry and is quite widely available.

I'm going to prime and paint the visible areas inside the cabin; I'm not doing the exterior for a few years. Once that's cured I will pump up the high-tech ACF-50 applicator!

Brian,
I think you've made a good decision. Take a look at this "corrosion map" from Cessna's Supplemental Inspection Document (SID).

Click to Enlarge

With you plane based near Dublin the axiom "an ounce of prevention is worth a pound of cure" comes to mind. For what it's worth Cessna recommends Cor-Ban 23 or ARDROX AV-8 in SEL-51-01.

[170C]

Does a continuously oily belly count as corrosion protection? If so I'm good.

[GAHorn]

Does a continuously oily belly count as corrosion protection? If so I'm good.

Unless it’s coming from that small hole in your sump just forward of the carburetor....(caused by corrosion)...

[c170b53]

Well, ( getting too serious here) oil will attract and retain contaminates against the skin. Adding Combustion components to that mix for extended periods won’t be beneficial either.
Being somewhat frugal, (not serious here) it’s the 5 knots increase in speed and gas savings that gets the creeper out, to clean and wax the belly.
OK, I guess you guys saw through that.