Was this area painted in an attempt to hide existing corrosion?

https://cimg4.ibsrv.net/gimg/pprune....36fd090762.jpg
https://cimg5.ibsrv.net/gimg/pprune....31fbfc6871.jpg
https://cimg6.ibsrv.net/gimg/pprune....9bcc60cfdc.jpg
My corrosion photos on N75276 - awaiting photos from the donor and have an A&P going to look it over on Wednesday when he returns from a trip to Mississippi.

This looks very scary.

Help me get oriented please. I assume the top two photos show corrosion of the spar cap which was exposed after removal of the fuel tank. Are we looking at the lower spar cap or the upper spar cap? If the staining indicates flow of water (or something else) I assume this is the upper cap. If that's true then what trapped water there.

I think not. I doubt it's original Piper paint, as I doubt that Piper would paint the plumbing, but the paint was uniform in the area, and had been there a while.

Ebbie,

The corrosion in your photos has been there for many years. That type of corrosion does not "suddenly appear". As it is intergranular exfoliation corrosion, once it starts, it's really hard to stop. Corrosion preventing liquid is the best hope, but that spar is way past that!

Ebbie: Re post #22
I've seen wing spar corrosion in the fuel tank area a few times before on PA28s. Looks like galvanic action caused by the steel anchor nut may have set that off. All for want of a decent coat of primer or smear of jointing compound ...
I'm curious whether your previous few Annual Inspections had called for tank removal? Good inspection should have caught the corrosion in its early stage.

The fuel tanks have not been removed from my PA-28-180 in at least the last 20 years. Several different inspectors have signed off this aircraft and none has required removal of the tanks. None of the Piper mandatory SB or resulting AD has, to the best of my knowledge, required removal of the fuel tanks. If this was a commnon problem I would have expected a mandatory SB and an AD.

Have any of the PA-28 with spar corrosion hidden by the fuel tanks been hangared or were all kept outside in the weather?

I'd be very concerned in that case, you could be flying on borrowed time. Google Piper SB 1006 and EASA Airworthiness Directive 2005-0032. The hidden spars are supposed to be inspected at seven year intervals. Your maintenance technical records department should be aware of that.

There is no requirement in USA to comply with a Piper Service Bulletin unless it is invoked by an associated Airworthiness Directive. I can find no FAA AD that requires compliance with SB 1006. The only reference I found to SB 1006 is here - https://www.federalregister.gov/docu...-inc-airplanes

That reference says recent compliance with SB 1006 is not sufficient to meet the requirements of that AD.

I'm not saying that removal of the fuel tanks every 7 years isn't a good idea. I'm just saying that I'm not aware of any FAA requirement to do so. I don't doubt there are many PA-28 flying in USA that are not compliant with SB 1006.

I saw a few queries.

Not sure why it was missed on previous annuals, especially the one immediately after it sat on the ground on Guadeloupe for over a year.

The tank has been off for sure - in 2018 it got a hole poked through the wing when it slipped off a wing jack - got repaired in St. Barths - took the opportunity to do the training to land there (long expired as they last on six months - didn't find it difficult to land there, Canefield in Dominica is much scarier, especially landing south to north)

That said, it is what it is.

The donor plane a 1984 is about to get inspected, seems the A&P has been very busy.

Fingers crossed that the wing is good, I have a couple of photos but they don't show just where I am keen on getting looked at.

Or several other corrosion related bulletins mentioned in Post 20. Its been my experience, if operating a Piper product around salt-laden areas or near urban-industrialized areas, an owner's decision not to address those known corrosion areas usually ends up in a similar result. Preventative/proactive maintenance can be everything in some circumstances. And as these legacy Pipers get even older once these areas are finally noticed it a bit late to simply repair the area.

A fascinating thread. Thanks.
Seer

Have there been many instances of in-flight structural failure of older Cessna and Piper airframes due to corrosion?

In the UK do corrosion inspections form part of the maintenance schedule for ARC renewal?

An Australian Cessna 210 lost a wing due to failure directly attributable to corrosion:

https://www.atsb.gov.au/publications...ir/ao-2019-026

There have been other structural failures in Cessna and Pipers where corrosion of primary structure was a factor. In the case of Cessnas, the "SID" inspections are pretty thorough in defining what inspections should be done. Whether mandatory or not, a GA airplane owner would be foolish to dismiss these inspections as not necessary. The Cessna SIDs, in particular, are really well written, and obviously based on a true understanding of the vulnerable areas of the structure of the legacy planes based on decades of experience.

About 1985 we had to inspect Pa 28-140 wing spar roots for corrosion due to an AD. I was working at Bristol at the time.

As mentioned there have been a few in-flight structural failures to include various wing strut failures, however, in my experience the majority of severely corroded primary structures are usually found during other maintenance actions similar to the OPs situation. Where corrosion does directly cause more "flight" accidents/incidents with SE small aircraft is when it's related to internal engine components, airframe fuel systems, electrical connections, etc.

There have been PA-28 wing separation accidents due to fatigue cracking and also due to structural overload. However, I am not aware of any PA-28 structual failures that were attributed to wing corrosion.

If there are any perhaps someone would provide references.

Is there a report for the Pa 25 accident at a wedding in South America where the wing folded during a stunt. Plane flew over and dumped the contents of its hopper after which a wing folded. Is there any similarity in the Pa 25 and Pa 28 wing.

Not even close! The PA25 is a strut-braced, fabric covered wing and the PA28 is an all aluminum cantilever wing.

Don't recall any in-flight corrosion failures but there were a few PA-28 loose wing discoveries on the ground due to corrosion that would have led to an in-flight failure had they not been found. SB 1244 and an FAA SAIB were issued subsequent to those findings. Fortunately the Piper design can withstand excessive corrosion in key areas.

No. The PA-25 used top braced PA-18 Super Cub wings which became metal-covered in later models. And doubt you'll ever see a report out of MX on that PA-25 accident.

Apologies, I was thinking Pa 36 which probably has no similarity also.