REFINISHING AN AIRSTREAM INTERSTATE'S ROOF, PART 1: SEAMS

Very quick blog post here just to describe how I began the roof improvements on our 2007 Airstream Interstate.  Life being generally imperfect, I was more-or-less forced into completing some caulking ahead of what I would have preferred, schedule wise.  Same thing goes for this seam repair.  Here's the thing you should remember about rust:  It doesn't progress linearly as much as it does exponentially.  Once it starts, you can't wait, so the rest of life's schedule has to be damned.

So, for example, a seam like this might look a little bit iffy and discolored for a long time, but once that rust gets a good grip, it's going to accelerate.  It gets worse at a faster rate the longer it's left unattended.  There are users on Sprinter Forum who report it quickly penetrating all the way through such that they had holes to patch.   

Once you see this bubbling thing start to happen, you do not have much time left.

After inquiring as to the optimal approach with about half a dozen differences sources, including via this Sprinter Forum thread, I decided to use POR-15 products for the first stage.  Here are the general instructions:

(1) Assemble your PPE - ear plugs, safety glasses, hat, filtering facepiece.

I despise all this stuff, but it is absolutely necessary for this job.

(2) Angle-grind your seams using a circular wire brush attachment.  Get as much of the existing paint and loose rust off the seam as possible.  I used finer bristle to start with because I thought fine bristles might get into the roof's lap weld joints better, but look what happened.

God almighty, I did not need this today.  Bristles kept breaking off, launching, and stabbing me like spears.  Because of the crazy angles involved with working around existing roof appurtenances, it's hard to keep the danged angle grinder machine guard between yourself and the rotating part, so be mindful of this possibility.  Imagine what could happen without safety glasses.  Regular nearsightedness glasses are not enough, which is why you see me using OTS (over-the-spectacles) safety glasses above.  

(3) Apply POR-15 Metal Prep spray to the ground-down seams.  The quart size comes with a spray nozzle attachment.  The instructions say to leave it set and do its work for up to 30 minutes on heavily-rusted areas.  As it turns out, most of my seams really didn't look that bad once I took the grinder to them - the rust had not penetrated that far, thankfully.

It will start to make a white froth like this when you first put it on.  That's the zinc phosphate-related chemical process in action.  I had nitrile gloves on, and I used my index finger to rub it into the seams.    

(4) After it has finished reacting, wipe off any excess and allow it to air dry.  In my case, I had very intentionally chosen one of the three whole days this entire winter where we had a dry front come through Houston (one of those other days, I had used for the caulk job).  I didn't have to wipe any excess, because it air dried in its entirety within about 20 minutes.

(5) Open up your pint of POR-15 Rust Preventive coating and do some major stirring.  You also might want to consider swapping that filtering facepiece that you used during grinding for a full VOC respirator, because this is some nasty stuff.

 If you are really smart, you'll buy yourself a blank (empty) quart paint tin at the big box hardware store, and dump your pint of POR-15 into it, because the amount of mixing it will require is best served by having a lot of freeboard in your can.  I picked the silver color and it was chock full of settled solids.  It needed major homogenization.  I had to use two sticks to mash the solids all around and break them up.  This stirring took about 15 minutes and I still didn't think it was optimal. 

(6)  Apply the POR-15 coating to the seams.  And obviously it's difficult work, getting around everything else you might have on your roof.

I had to cut the solar wires' zip ties loose from their adhesive fasteners and prop the wires up with blocks of wood so that I could paint underneath.  What a pain in the a$$.  Of course the whole while, I'm contorted into strange poses on the roof of the van, stretching myself around the Fantastic and trying not to do a face-plant in the solar panels.  Fun stuff.  

I used a disposable foam brush to apply this because that's what I saw in a POR-15 webpage showing a product application scene.  Foam works well to squish the paint down into the seams as much as possible.

I wasn't very concerned with the cosmetic appearance of the resulting paint because my intention is to re-coat the entire roof with Bus Kote, so this POR-15 initial layer is going to get covered up anyway.  That process will be described in Part 2 of this blog post.

Incidentally, when I went to my local Tasco Auto Color store today to get these two POR-15 products, the place was full of professional painters picking up supplies because it was a Monday morning.  They advised me not to even buy the preparation product.  They said, "That POR-15 paint is so good that most people who use it don't even sand down their rust, let alone treat it chemically.  They just paint right over the rust and it does fine."

But I decided to be as thorough as possible, so there you have it.

My van is looking better every day, even though my paint job was nowhere near this elaborate. 

EDIT, January 29, 2017:  The POR-15 coating container clearly instructs to add multiple coats.  When I climbed back up on my roof a day after the first coat, I noticed that it had bubbled where it contacted bare metal - the paint itself is chemically-reactive, in other words.  Therefore, multiple coats are essential or else you'll be left with "holes" where the bubbles formed.  So I added a second coat, and when the weather is once again suitable, I will climb back up and evaluate whether it needs a third.