DP50 Primer Prep

[szicree]

Here's one for the experienced airpplane painters. Most epoxy primers like dp50 say to sand bare metal to around 150 grit (I'm talking about exterior paint here). I've heard of scotchbrite instead, but there's a big difference between that and 150 grit. So, what is the standard practice in the pro shops?

[tcrv7]

On our sprintcar hoods we use the grey scotchbrite pads it comes pretty close to 150 grit results Then follow up with the rose colored pad YMMV

[az_gila]

Originally Posted by szicree

Here's one for the experienced airplane painters. Most epoxy primers like dp50 say to sand bare metal to around 150 grit (I'm talking about exterior paint here). I've heard of scotchbrite instead, but there's a big difference between that and 150 grit. So, what is the standard practice in the pro shops?

Steve... aren't they usually referring to a steel substrate here??

I would think 150 grit will get through the Alclad layer...

I think my paint shop was a red ScotchBrite user (closer to 400 grit)....

UPDATE... got the 400 grit a bit wrong.... I like this chart...

The one with the pink background on this page...

http://users.ameritech.net/knives/grits.htm

... gives maroon (better than my red description) as 220-280...

gil A

[deene]

Aluminum is softer than steel and will require a finer abrasive. As several have pointed out, sotchbrite is normally used along with a acid etch followed by a surface conversion. I just finished my RV8 fuse will PPG primer and I used the grey scotchbrite along with Dupont 225 and 226 etch and conversion materials. Also the scotchbrite material holds up well in wet applications like this.

In all cases, the paint manufacturer will have specific recommendations depending on the substrate being painted.

Deene Ogden
EAA Tech Counselor/Flight Advisor