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Why did this paint fail?
https://www.rypn.org/forums/viewtopic.php?f=1&t=27860		 Page 1 of 2
Author:  robertmacdowell [ Thu Jul 30, 2009 12:18 am ]
Post subject:  Why did this paint fail?
http://www.wolfharper.com/rail/pres/wm75before.html
This locomotive gets run down a line where the tree branch trimming is insufficient, thus it tends to get scraped by brush. But I don't think that's the reason. We're about to repaint it and I want to not have this problem again. Ever.

What do you think?
Author:  David Johnston [ Thu Jul 30, 2009 2:10 am ]
Post subject:  Re: Why did this paint fail?
What paint system was used to paint the locomotive?

When I see the finish coat fall off the primer, I wonder if the recoat times were followed and if the primer was dry (free of moisture) when it was recoated. Did the primer require sanding prior to recoating and was this done?

Was the locomotive sand blasted prior to this painting? Was it free of rust when primed? Was it colder than recommended when the primer was applied? Was the primer properly reduced? Was the surface free of dust and oil and wiped down with solvent just prior to priming? Is the primer specifically designer for steel? Do the engine compartment temperature extremes exceed the capability of the paint?

There are lots of ways to screw up a paint job.
Author:  k5ahudson [ Thu Jul 30, 2009 6:33 am ]
Post subject:  Re: Why did this paint fail?
As David Johnston said, there are a lot of ways to screw up a paint job.

We need to know what type of paint was used? Preparation? Primer? How much time there was between applying the primer and the base coat? Judging by the color of the undercoat, was a primer even used? Is that the previous color of the engine?

Bottom line, if you don't know anything about paint then at least get some advice from someone who does. You just can't slap any old paint on and expect it to last.
Author:  Alexander D. Mitchell IV [ Thu Jul 30, 2009 7:47 am ]
Post subject:  Re: Why did this paint fail?
Honestly? As someone who has quite a bit of experience with outdoor painting, I have to ask: Was this darned thing even brought down to bare metal first, let alone primed? Seriously, this looks like a bad paint job with cheap spray paint cans.

Echoing others' sentiments, we need to know exactly how this was prepped, primed, and painted.

The quality of paint makes a lot of difference. One contractor I was working with had a fleet of rental trailer tanks, and had lots of chalking, flaking, etc. They switched to a two-part system from Ponderosa Protective Coatings of California: a battleship gray primer (I think OrganiClad) and a custom-tinted sky-blue two-part catalyst-activated Acryliclad. Those tanks are holding up to outdoor use/storage just like locomotives, as well as on-site abuse, regular power-spray washings, etc. Expensive? Hell, yeah. I remember hearing a price of around $45 a gallon for the color coat, plus the little pint cans of catalyst to be added prior to spraying (think paint pots just like auto body shops).
Author:  Rob Gardner [ Thu Jul 30, 2009 12:07 pm ]
Post subject:  Re: Why did this paint fail?
Not to be a wise acre, but how about trimming the trees along the ROW once the effort and money has been spent to repaint the engine?

Rob Gardner
Author:  Dave [ Thu Jul 30, 2009 12:29 pm ]
Post subject:  Re: Why did this paint fail?
Looks like poor surface prep followed by bad bonding between primer and cover coats. BTW, from what I could see of it, the other bits of the consist don't look so good either.

If stored outdoors, don't expect an amateur paint job to last more than a few years in any case.

dave
Author:  Randy Gustafson [ Thu Jul 30, 2009 1:57 pm ]
Post subject:  Re: Why did this paint fail?
If you don't think that getting a decent paint job is rocket science, I beg to differ.

As I was researching paint jobs and methodologies and how to spec and test, I came across this gem. This is how NASA tested paint and painting systems. I was particularly interested in the fade results, but going back and checking this you can also see they documented at what temperature the primers failed.

This is borderline crushingly technical, but it covers many of the same issues in painting railroad equipment and leaving it outside. It's just brutal.

http://corrosion.ksc.nasa.gov/pubs/268-86b.pdf
Author:  o anderson [ Thu Jul 30, 2009 3:19 pm ]
Post subject:  Re: Why did this paint fail?
It looks like the bonding between the primer and the finish failed. This can happen a lot of ways but I think the most common is timing. With volunteer labor it might be several months between when the prime coat and the finish coat are applied. This is enough time, in sun and weather, to develop oxidation on the prime coat which is what keeps the bond from being good. I have sanded and repainted prime coats more than once before a finish coat, just to ensure a good bond. Keeping the object out of the weather can help preserve your primer, but the best thing would be to work fast and get it all done quickly, while the primer is still fresh.
Author:  k5ahudson [ Thu Jul 30, 2009 7:36 pm ]
Post subject:  Re: Why did this paint fail?
Randy Gustafson wrote:
http://corrosion.ksc.nasa.gov/pubs/268-86b.pdf

Can't NASA afford a spell checker.... "FOREWURU"....."PKOCEUURES"....."ACKNUWLEOGMENT" ..... Holly crap!!! :P
Author:  Jdelhaye [ Thu Jul 30, 2009 7:39 pm ]
Post subject:  Re: Why did this paint fail?
k5ahudson wrote:
Randy Gustafson wrote:
http://corrosion.ksc.nasa.gov/pubs/268-86b.pdf

Can't NASA afford a spell checker.... "FOREWURU"....."PKOCEUURES"....."ACKNUWLEOGMENT" ..... Holly crap!!! :P

Sounds like typical errors from optical character recognition.

Jeff
Author:  Harry Nicholls [ Thu Jul 30, 2009 7:43 pm ]
Post subject:  Re: Why did this paint fail?
It appears to be primer failure. Rust under primer is a factor and it should be neutralized with phosphoric acid before priming. Also, it appears the paint did not adhere to the primer - are they different products and are they compatible?
Author:  Dave Wolven [ Thu Jul 30, 2009 11:22 pm ]
Post subject:  Re: Why did this paint fail?
Why did this paint fail after only 4 years?

Whithout touching the paint, its hard to tell. I would say the paint was latex base and the rain and snow went thru down to the metal and then as soon as the rust started it just pop it off.

This is a mess and to repaint will require SAND blasting until All the rust is gone then treat the metal with Rustmort to kill what may be left. after 24 hours wash with water. when dry, coat with apoxy primer. This a sunny day job temp needs to be 75 or better.

We have had good luck using Northstar 2 stage. Last gallon cost $105.00 and that depends on the color you need, I used red
Dave Wolven O.E.R.M.
Author:  robertmacdowell [ Fri Jul 31, 2009 9:41 am ]
Post subject:  Re: Why did this paint fail?
I have more info. I would have photos but I can't find a hotspot in this town.

The paint was blistered four years ago when last painted. The crews chiseled up all the blisters back to paint that was not delaminating. The recent paintjob is performing well where on bare metal. The failing areas have at least 4 coats of paint on them. I count 10-12 layers depending on lettering and if you count a very thin dark gray layer beneath the oldest black.

Where bare metal is exposed, all layers of paint are blistering away, I presume the original primer is failing when exposed to weather. But it also fails far into intact paint but in a different place. As far as six inches away from any damage, a putty knife will peel away all layers above the oldest black, so it seems to me there is poor adhesion between those layers.

Is this common with GE 44-tonners? Is there any recourse other than taking all the old paint off?
Author:  Dave [ Fri Jul 31, 2009 11:32 am ]
Post subject:  Re: Why did this paint fail?
Advice by remote control - take it for what it might be worth.

Strip it with aircraft stripper down to "bare metal", which won't actually be bare, but will get 97% of the built up crap off. Clean and neutralize.

Remove all doors, hoods, whatever can be unbolted and mechanically remove all coatings and grunge down to true bare metal. Remove and treat rust. Do any bondage or other body work at this stage and prime with a good self etching automotive grade primer that will bond with your chosen cover coat system when the climate in the paint shop is favorable.

Mask off all innards, openings, etc and do the same to the carcass.

Assemble it, do any spot bodywork / panel fit adjustment, whatever.

Scuff and cover coat as recommended during favorable climate.

I've had some good luck with the base coat / clear coat systems in that it is easy to mask and touch up the flat base coats to perfection before sealing with the clear overcoat. When the clear covercoat gets scuffed, it can be solvented and recoated.

It sounds as if it is overdue for a complete stripping and repainting.

dave
Author:  robertmacdowell [ Sat Aug 01, 2009 6:37 am ]
Post subject:  Re: Why did this paint fail?
Finally, internet. Here are the paint layers.

The blisters fail between bare metal and first prime coat. When peeling blisters, the putty knife will keep going with little effort, but the failure point will shift to between the first black and next prime coat. The museum received the locomotive in green paint. They painted the light-barn-red 14 years ago and the black on white 4 years ago. As said, the black on white has performed well where on bare metal. Otherwise it is constrained by the performance of the underlying paint.

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