Paint question. Color showing up during sanding?

[GilK]

I'm going to start off with a short back story. I bought my 1960 Arkansas Traveler and it had the registration numbers painted on the boat. There is some whitish paint with black letters. Cool I don't have to worry about stickers coming off. I get checked by FWC after fishing yesterday and find out there needs to be some spacing between the letters and numbers.
I went this morning to Tractor Supply and got some paint that is supposed to stock to aluminum and some 600 sand paper. I'm just doing a block for the numbers because it only needs to last a year or two until I make this boat a project which will involve a paint job. I started sanding over the painted areas to clean the area and give the new paint a little surface to adhere to. I decided on 600 grit because it's just semi temporary and I'll be doing it correctly when I paint the whole boat. Under the "white" paint I found a blue layer that I think is the original paint. You can see this in the picture below around the FL.

I started on the other side and went a little bigger on the area (I did get my safety inspection decal yesterday) so I could put the decal on a white background to make it stand out more. And the blue color started coming out when I thought I was on bare aluminum.

Does anyone have an idea on what is going on? It made sense under the paint, but not where I thought it was bare aluminum.
Thank you for any insight here.

 

[ripdmup]

Maybe you hit some gray primer. Can`t say really. What I can say is "Keep Sanding" and good luck with your project

 

[MrGiggles]

Looks to me like you have a couple different layers there, silver over the top of the blue/green. Might be the aluminum paint made for roofing.

 

[thill]

If the existing paint is solid, has good adhesion and isn't flaking or bubbling, I would clean and scuff itup a little, and then do a test patch of your new paint.

If it bonds well, doesn't make the old paint bubble or anything like that, and gets nice and hard, your primer coat is already done. Give it a nice topcoat.

The idea that you have to strip off well-adhered layers, only to HOPE what you put back on will adhere as well doesn't make much sense to me, but to each their own.

 

[ripdmup]

The idea that you have to strip off well-adhered layers, only to HOPE what you put back on will adhere as well doesn't make much sense to me, but to each their own.

Seems a backhanded comment there, so I will respond. It looks like the boat has been completely striped clean. Why not keep sanding to completion. Or completely bare, just so there is no misunderstanding about what I just said. I have reread the postings in their entirety and no where can I find the word HOPE or any interpretation of the word HOPE. To the OP, I HOPE your boat turns out great.

 

[LDUBS]

Seems a valid point that if the existing paint is sound then there is no need to sand down to bare metal.

 

[thill]

Seems a backhanded comment there, so I will respond. It looks like the boat has been completely striped clean. Why not keep sanding to completion. Or completely bare, just so there is no misunderstanding about what I just said. I have reread the postings in their entirety and no where can I find the word HOPE or any interpretation of the word HOPE. To the OP, I HOPE your boat turns out great.

My post was not meant to be backhanded or snarky.

According to his original post, he was scuffing the paint, and some color from earlier paint layers started showing through. So as Mr.Giggles pointed out, there is clearly a silver paint over the blue.

Hence, my comment that IF the paint layers seem well-adhered, to test an area with the new paint. If it bonds well, he can paint it with good success, without the need to strip the whole boat down to bare metal. If it doesn't adhere well, then of course, he will need to do more work.

This will help him get his numbers done now and will help him make the best choice when he does the full paint job in the future.

ALL of us hope he has good success.

 

[GilK]

Thank you all for the replies. I've been extremely busy with work this week. I just painted an area big enough for the numbers and safety decal.
After reading the replies, I'm thinking that the underlying blue color is whatever Southwestern (I think that's the manufacturer) used on the bare aluminum to prep it for paint and what I thought was bare metal is actually a silver primer. There are still remnants of the original blue paint on the boat. The original logo is still barely visible on one side. I'll get pictures this weekend.

 

[LaqueRatt]

For the record IMO and after painting many many things, I have to say thill is correct. For a paint job to be successful it 1. Has to look good. No bubbles or runs, no chipped edges showing. 2. It has to stick. Basically the surface has to be clean and sanded. Anything loose will come right off with a DA. What won't come off gets feathered in.

Something some never quite grasp is an item can be stripped completely or have 10 coats of paint on it and when prepped properly you can't tell the difference except without a thickness gauge. So do whatever is easiest. In some cases the existing paint bond is so fragile that it is smarter and easier to remove all the paint. You sure don't want to leave any loose paint behind. Very seldom is this the way to go though.

Sand, clean, and paint using whatever paint and method suits your skill set. I sometimes spray, but it makes a mess, is hazardous to your lungs, and wastes a good share of the product. So when possible I roll with a closed cell roller. When done properly it leaves zero orange peel behind and if you're going for a high luster paint job you got to get rid of all that, so best to avoid it from the start by rolling and what can't be rolled gets dabbed with a foam "brush." I like to use Penetrol as a drying agent/hardener and also because it makes the paint lay down cleanly, with no bubbles and no peel.

Seems painting is one of those subjects people like to disagree on, but with a little practice you can make stuff look like new without spending a lot of cash or investing a lot of time. I prepped and painted a 14' AlumaCraft last spring, two colors, and I spent a total of 4 hours on it. Including a coat of poly on both sides of the transom wood.

 

[GilK]

That looks pretty good LaqueRatt. Have you found there is much of a difference between brands of closed cell rollers?
Here are a could pictures of where there is still some of the original paint.

And here is a picture of what my quick paint job looks like.
I'll probably paint above the line white in the near future.

 

[LaqueRatt]

If there is, I've not noticed. Your quickie paint job looks good from here! Seems some obsess over repainting a boat. Guess maybe if you never did much painting you worry you'll make a mess out of it, but really you just need to knock off the loose stuff, feather the edges (optional) and make sure it's clean. I used an aluminum paint on the Aluma and the can said to prep it by wiping it down with paint thinner. That's all I did. I never even took any soap to it. Paint thinner and a bunch of old towels got her clean as a whistle. I did go over it twice though just to be sure.

 

[thill]

Looking good! I can't see any evidence of the old paint, so you did a good job prepping.

Now that you have practiced and can see how clean it will look, doing the rest won't be so daunting.

 

[GilK]

Looking good! I can't see any evidence of the old paint, so you did a good job prepping.

Now that you have practiced and can see how clean it will look, doing the rest won't be so daunting.

Yeah. I'm going to paint above the line white with the same paint. Below the line is going to wait until it becomes my full project (floor, pour foam, console for remote steer motor) and I'm currently thinking about using the bottom coating for airboats, since I do beach it on islands in the river.

 

[LaqueRatt]

I left the bottom of my Aluma bare and painted about the water line with aluminum paint. Almost couldn't tell the difference. Why coat the bottom if you know it'll just get messed up?

 

[thill]

I left the bottom of my Aluma bare and painted about the water line with aluminum paint. Almost couldn't tell the difference. Why coat the bottom if you know it'll just get messed up?

Protection from crevice corrosion would be my biggest reason. Water gets under the heads of rivets and starts doing it's thing. Even a quickie paint job should help slow down that process.

 

[GilK]

I left the bottom of my Aluma bare and painted about the water line with aluminum paint. Almost couldn't tell the difference. Why coat the bottom if you know it'll just get messed up?

You're boat looks good. The reason for the bottom coat is Salt water. Most of its time it'll be in the Indian River so that extra barrier will help with corrosion. And the airboat coating will resist the damage beaching will do.