Since the weather seems to have turned for the better, Mark has been working on the Purdue crane and I thought I would post an update. The first shot below, shows Mark using an air compressor to remove any loose paint/primer that is still on the bad side of the crane. Mark also discovered that since the original Orton paint and primer came off this past winter, a number of codes impressed into various steel panels have been exposed. A close up of one of the panels is shown in the second shot. Note the Orton builders number 44596. Finally, a shot taken at the end of the day showing the primer that was applied. Yellow finish coat coming up!

Les

Mark put the finishing coat on the Purdue crane this week!


Les

Hoosier Valley does a tremendous job of paint; it's one of the first things that strikes me when I visit - Everything Is Painted. You've left nothing for the Flickr photographers. I have a lot of respect for that. (even if I did work for Flickr's parent company.) That is the most important thing, and nitpicks over *how* you paint are really of second importance. With that in mind...

Not all surface issues are the painter's fault. GE did not like to pickle their steel, they painted over mill scale. This works as an anti-rust coating until 50 years later, it suddenly doesn't, and the job fails from the bottom layer. I have also seen railroad shops fail to remove surface contamination, causing separation between the factory and first shop paint jobs. Obviously any delamination between layers *below* yours are not your doing.

I always do two things: #1 Roughen the layer so it has some "tooth" for the new paint to mold into and engage. A glossy surface is like trying to paint glass, you know how easily it pops off with a razor blade. #2 clean the surface of contaminants lest it act as mold release.

Now in the photos above, I see either stout sanding, wire brushing, or media blasting (I'm guessing not the latter). All these will provide an excellent "tooth" for paint to adhere, which should lick the problem. When I saw the crane a few years back I noticed the paint was still holding gloss, and I think that's what gotcha.

Someone commented that rusty pieces take paint better than glossy ones. That's true; rust has tooth, and the stuff you do to knock off the surface rust has even more tooth. However painting over rust is still bad news, as NASA's corrosion website discusses at length. Like everyone else they are searching for the "paint over rust" holy grail; they have tried all the stuff from the back of the hot rod magazines in genuine testing and none of it works. Rust, left on the surface, is most likely to be the seed of corrosion from the inside.

What color and what manufacturer are you using?

Later!
Mr. Ed

Mr. Ed -

See my comments about paints and primers earlier in this thread.

Les

OK. Thanks!

Mr. Ed

One thing I have noticed when this happens is that surface prep does not really seem to make a difference. I have had this exact thing happen (on 1/4" plate!", and you can sand, wire wheel, etc all day long, and it will do it again. Paint quality I am sure does make a difference, but the rapid temperature changes are the major culprit. Stripping ALL of it again does help, as once it starts doing the crack and peel, it will all do it down the road unless you get it all off and start fresh. Feathering the edges out does not make a difference.

- He who goes through this on the water, every year.