New Struts, a corrosion warning

[Robert Lees]

I purchased some new sealed struts from one of the suppliers back in January 2008 after the AD came out. I remember them coming very well packaged and primed with what appeared to be a reasonably tough green primer, so I wiped the primer down and painted them with a two-part etch prime (to adhere to the existing primer), then two-pack epoxy primer then two-pack top coat.

They were fitted to my aircraft in about April 2008.

Last year, a little bit of corrosion made itself apparent, so this annual I decided to strip them back. In some areas, large sheets of the primer almost fell off; in others it's quite well attached.

You can see from the photos below some of the corrosion that did not show through the paint. Note that I did not use powder-coating. Note also that there was no bead-blasting prior to their primer coat.

To be fair to the Supplier, these struts are now six years old, done about 450 hours. The corrosion is not what I would call "significant", so it's just a warning to those who purchased new sealed struts at about the time the AD came about to be vigilant.

If you had your struts powder-coated, be extra vigilant! It could take many more years before the coating shows evidence of surface corrosion.

Rob

[Hank Jarrett]

Re: New Struts, a corrosion warning

OK, this might need to be looked at with a "Tribal Inspection". On my annual prep I found a little loose paint and very minor corrosion on the fuselage end of my front pilots strut. So minor I just fixed it and went on my way, but two planes worries me. We need to all go look, NOW and report back so if there is a problem we can nip it in the bud and avoid the FAA doing something draconian to us.
I will be looking at my other 3 struts VERY carefully next time out. By the way, I also do the cluster inspection on each annual (even if it is a one time inspection). I found the touch up paint from the last inspection pealing. I repainted the tubes in the area. My opinion, I didn't clean it well enough before painting the last time. While I am in there I also inspect the cluster at the front of the gear legs. Paint pealing there too.

Hank

If we keep our planes in good shape the FAA won't think they have to force things on us.

[adrozell]

Re: New Struts, a corrosion warning

Always keep touching up the paint. Might not always look good but keeps the rust away. I always hit the struts and landing gear. The plane always seems to chip of there. Just spot treat any rust and dab on sum paint. Not to good when you get it under the prim though Will keep an eye out. Here in texas it is not to bad dry most of the time, never have seen any thing more than surface rust. Might rust threw if not touched in 15-20 years. But like to be safe.

[mike lutz]

Re: New Struts, a corrosion warning

I had to remove my sealed and recertified struts after two years service also.Noticed little blisters appearing all over them in several areas ,so sand blasted and started over with two part epoxy primer.Put on two part polyurethane paint and things are still good two years later.I question the cleanliness when they were sealed and certified by the vender,fabricator.I also have a new manufacture set of struts on another airplane from the same supplier with no problems so far.

[Dennis Keels]

Re: New Struts, a corrosion warning

Hank by the time you done inspecting there won't be enough day light left to fly.

[adrozell]

Re: New Struts, a corrosion warning

May just be in bad prep by one guy at the fab shop. My stuts look just as goog as ever. And I put them on at the time of the ad. Nothing more than touching up chips since. Just the normal enamal paint nothing special.

[Hank Jarrett]

Re: New Struts, a corrosion warning

By the time I get the inspections done "DAY" isn't meaningful anymore. The YEARS have gone by!
The corrosion I saw on my struts was generalized over an area you could just cover with your hand. Not small blisters, just a very thin layer of rust on the surface of the metal under the primer. If you put your palm on the paint and twisted if sheared off in a sheet showing a light coating of red dust under it. Kind of looked like the bottom end had gotten a light coat of surface rust and it was painted over. The paint may have never been stuck to the metal and was like a layer of "plastic" wrapped around and unbroken. The base metal had no pits of damage, just a light coat of red dust under the paint. The whole strut got a good scrubbing clean to see if there was any more loose paint with none found. I think I had a painter who didn't wipe the metal down before painting.

Hank

Hank by the time you done inspecting there won't be enough day light left to fly.

[N96337]

Re: New Struts, a corrosion warning

Any primer, even epoxy primer, is porous. Unless the primer is specifically formulated and applied to be a primer/sealer, it is porous like a sponge (that's one of the things that makes it a great primer) and will hold moisture/contaminants to the surface. Then add a poor prep job at the factory and you come along and paint over that and seal it all in.....you're going to get corrosion. I can't count the times I've had to explain that to people when I was tech-rep and how many people would argue with me about it.... "I've done it this way for years and never had any trouble"....yah right. I've seen countless times that someone would receive parts that are primed and just let them sit for days/years and then have a problem when they paint or a while after. When I get parts in that are primed, such as struts, the first thing I do is strip the "factory" primer off and get them prepped and some good primer on, then after they outgas, some topcoat applied will seal them and prevent a problem.
John

[astjp2]

Re: New Struts, a corrosion warning

What we dont want is another REDICULOUS AD because someone didnt prep their parts correctly before installation....that is not a manufacturing issue, its just bad maintenance....

[M Towsley]

Re: New Struts, a corrosion warning

Great info, John. I never realized some of what you related. Informative thread even if you don't have newer struts.

[flyguy]

Re: New Struts, a corrosion warning

I was told that some years ago several airlines had problems using a "new" paint. I think they did a single coat of epoxy, assuming it was a miracle substance. They wound up with corrosion all over under the new paint. I believe they referred to the corrosion appearance as "worm tracks." Was a lot like what I see in the photos here. Whatever the paint was, the problem was blamed on porosity as mentioned.

Edit: just thought of this----I wonder if those "worm tracks" conform to Chaos Theory? Chuckle. Knew I should have avoided that last cup of coffee.

[jstall]

Re: New Struts, a corrosion warning

Interesting,

I bought or paid for struts thru "HARRY THE HUN" out of fear that there would be a run on them and none would be available? Well as we know he and his factory were bogus big time, in the end I got it in the end,
litterly lost 3500.00 finally struts were delivered reluctantly by the receivership of what was left of the factory, went to install them last year and guess what? Defective wrong strut angle and they don't fit. So I got my originals ultra sounded the 2nd time and re certified for another 4 years, they came thru with flying colors, no changes and totally good. I'm going to just keep doing this, there is nothing wrong and I am not having these problems whatsoever.

Sometimes the fix is worst that the bite, In my opinion the AD should be receded after the struts are inspected, Good vigilance and maintenance should be adequate in my opinion.

JS

[Hank Jarrett]

Re: New Struts, a corrosion warning

The technical name for Worm Track corrosion is "Filiform Corrosion". It was a PITA in the Navy.

Hank