Wet or Dry Sanding Aluminum?

[SoonerD]

I am refinishing a Crestliner Boat and have completely stripped off the old paint down to bear metal. Let me preference this by saying that I'm a complete "Rookie" and this is the first time I've done this to my boat and could use your "expertise". My question relates to wet sanding or dry sanding and don't know which method is best.

My plan is to use an etching cleaner (Phosphoric Acid) and use a wire brush to get rid of any corrosion on the bottom. I'm seeing some small black spots on hull and believe this is some type of corrosion. Then sand the boat, then spray two coats of Supermarine Etching Primer before painting. I am trying to understand if I need to wet sand or dry sand the boat? Also, there are small scratches on the port side of boat and wanted to know if I needed to sand them down smooth or if the primer would fill in the scratches and cover? Any advice would be appreciated. I have went to a lot of work and want to make sure that I'm doing this the right way.

 

[ondarvr]

Re: Wet or Dry Sanding Aluminum?

Wet or dry sanding won't really make a difference, if the directions don't indicate which is better for their product, then its up to you.
I dry sand.

Fill the scratches, most aluminum hulls aren't all that thick, so you don't want to remove material.

 

[Knightgang]

Re: Wet or Dry Sanding Aluminum?

Wet or dry sanding won't really make a difference, if the directions don't indicate which is better for their product, then its up to you.
I dry sand.

Fill the scratches, most aluminum hulls aren't all that thick, so you don't want to remove material.

Agreed...

Either way, sanding is sanding. When you see these car build shows and they are wet sanding a car, they are wet sanding for two reasons. 1. Usually there is a tad bit if soap in the water and the soap acts like a lubricant so that they can just remove the finish of the car without "scratching it" 2. The water helps to remove, wash awasy, the particles of dust that are being sanded off to keep frm scratching the car...

All you are doing is removing any residual paint and scruffing the surface enough that the paint will bond to the metal... Dry sanding is fine. Just be sure to clean well before painting....

 

[Bob_VT]

Re: Wet or Dry Sanding Aluminum?

I am refinishing a Crestliner Boat and have completely stripped off the old paint down to bear metal. Let me preference this by saying that I'm a complete "Rookie" and this is the first time I've done this to my boat and could use your "expertise". My question relates to wet sanding or dry sanding and don't know which method is best.

My plan is to use an etching cleaner (Phosphoric Acid) and use a wire brush to get rid of any corrosion on the bottom. I'm seeing some small black spots on hull and believe this is some type of corrosion. Then sand the boat, then spray two coats of Supermarine Etching Primer before painting. I am trying to understand if I need to wet sand or dry sand the boat? Also, there are small scratches on the port side of boat and wanted to know if I needed to sand them down smooth or if the primer would fill in the scratches and cover? Any advice would be appreciated. I have went to a lot of work and want to make sure that I'm doing this the right way.

Welcome to iboats. I feel you will no longer be a rookie by the time this project is done.

A few words of advice and some may echo what has already been said. I would avoid removing and material and I would NOT use the acid and a wire brush.

There is No Need to strip to bare aluminum and the places that do get stripped to bare aluminum can be primed with zinc chromate and only a misting is needed.

Take some time and look at the completed project section. If you have good paint on the hull now all you need to do is basically dewax, sand lightly (scuff it up) and re-paint.

Post a few photos of your project. You will get some expert advice here and you will also find out that the restoration site is about 50% aluminum boat projects right now.

 

[SoonerD]

Re: Wet or Dry Sanding Aluminum?

Thanks guys for all the assistance and I appreciate all the expertise and experience with users on this site. In terms of stripping to bare aluminum, I don't think I have much of a choice on the hull as it's pitted really bad and honestly think this boat has been in saltwater or near saltwater at one point. I will only use this boat in freshwater once restored. I just finished stripping the sides of the boat and fortunately the paint was so thin in terms of the number of coats that I was able to use a product called Citri Strip which didn't have any harsh fumes and did not contain any methylene chloride and I must say, it worked great. I'm not sure it would work that well if you had several coats to remove.

Bob VT, what is the difference between Zinc chromate primer and Gov't Spec Phenolic Alkyd Self Etching Marine Primer? Please excuse my ignorance, but I want to make sure I'm doing this right.

http://supermarinepaint.com/primer-etching.asp