3 Big SPI boxes on my porch, now what?

1A Rock

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This is my first post here, I'm sure it won't be my last, I have read and searched a lot. I am going to be painting an aluminum truck bed that is going to be aircraft riveted together. I want to epoxy it before I rivet it together. After that I want to spray a sealer coat of epoxy and single stage. My questions are, what grit sandpaper on the first sanding that the epoxy will cover in the aluminum,and give enough tooth for a strong bond. and any advice on cleaning the surface prior to epoxy? This bed is .050 6061, it does't need any body work, I have no intention of sanding at all unless I have to knock the Epoxy down to remove orange peal. Thanks in advance for your trouble.
 
Barry recommends 80# DA over bare aluminum before epoxy. That works fine if you apply 2 coats unreduced. Clean with 700 before sanding, then again after sanding before epoxy. Make sure you wait an hour or so after wiping, before epoxy.
 
You have to do the sanding the day that you shoot epoxy. Either that or use a aluminum prep wash just before you epoxy, (you still need to sand with 80-180 just not the day of) as aluminum oxidizes almost immediately after sanding. If you are not experienced, sanding with 180 grit on the DA is safer (and perfectly acceptable) than 80 grit, especially if it's a softer temper aluminum such as 3003. Even if it's 6061, 180 would be a better choice IMO. One other big thing is that you do not want to do any type of work on steel while your aluminum is in bare metal. No grinding, no sparks around your aluminum bed. Any ferrous metal that comes in contact with the aluminum will cause corrosion which will result in paint failure shortly down the road. Clean your tools, use fresh sandpaper, take any necessary step to ensure that doesn't happen. If you have also done steel work in the vicinity of the aluminum or don't know, then sanding, wiping it down with a W&G remover like SPI 700, then resanding is a good idea to help ensure that you don't have any embedded steel particles in the aluminum. All it takes is one and the galvanic corrosion starts, which results in the paint bubbling and failing in that area. Even the OEM's have had trouble with this. OEM's now state that any aluminum repair and refinishing needs to take place in a seperate area from where steel is worked on. Basically a separate facility. :eek: I know of 2 shops that are building/setting up separate shops just for their aluminum work.
 
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You have to do the sanding the day that you shoot epoxy. Either that or use a aluminum prep wash just before you epoxy, (you still need to sand with 80-180 just not the day of) as aluminum oxidizes almost immediately after sanding. If you are not experienced, sanding with 180 grit on the DA is safer (and perfectly acceptable) than 80 grit, especially if it's a softer temper aluminum such as 3003. Even if it's 6061, 180 would be a better choice IMO. One other big thing is that you do not want to do any type of work on steel while your aluminum is in bare metal. No grinding, no sparks around your aluminum bed. Any ferrous metal that comes in contact with the aluminum will cause corrosion which will result in paint failure shortly down the road. Clean your tools, use fresh sandpaper, take any necessary step to ensure that doesn't happen. If you have also done steel work in the vicinity of the aluminum or don't know, then sanding, wiping it down with a W&G remover like SPI 700, then resanding is a good idea to help ensure that you don't have any embedded steel particles in the aluminum. All it takes is one and the galvanic corrosion starts, which results in the paint bubbling and failing in that area. Even the OEM's have had trouble with this. OEM's now state that any aluminum repair and refinishing needs to take place in a seperate area from where steel is worked on. Basically a separate facility. :eek: I know of 2 shops that are building/setting up separate shops just for their aluminum work.
Any suggestions on an aluminum prep wash? thanks
 
i agree with chris here on the grits. i have found that 80 grit in general for alum is very aggressive and if you wipe it down after, the sanding scratches just pull all kinds of fuzz off the towel or rag you are using and you cant get it out. 120 is ok as well as 180. i have painted an ass load of alum over the years and while what chris says is all true, i think the oem's are making everyone a little paranoid. i have never had a failure on aluminum in 20 years using spi epoxy on it. doesnt matter if its been sanded/blasted that day or 2 weeks prior. could be that these recommendations are being made to cover their ass for the 1% that might be in just that perfect environmental condition for corrosion to start....who knows. i know i am not far from the shore here and the summer humidity is 95% constantly and i have never had an issue. this includes a ton of repairs work on aluminum components on boats that are sitting here right on the bay at a marina, some in the water lol.
 
I agree with both of you on the 180, just didn't want to give him anything but Barry's recommendation. The sprint car wings I paint get a thorough washing with Dawn and a red scotchbrite, then 180 DA, then 700 and shoot. A lot of them get epoxy only (2 coats) and have held up very well to a lot of abuse.
 
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