Can You Sand Aluminum?

[gazelle]

Hey folks

I am just about done stripping a 21 ft aluminum boat. Before repainting I wondered if it would be ok to sand the aluminum to get a few hard to remove specks of paint off and to smooth out a few spots on the bottom that had light corrosion. If it is ok to sand what grit do you suggest?

Other questions that are off topic but I would be interested to hear answers for.

1) interior is next years project. I really do not want to tear the floor out this year to gulvit all rivets. Is there something I could put on the outside of the rivets to help stop any possible leaks? I plan on filling the boat with water to see if there are any leaks. Obviously if any are fast leaks I will be pulling up the floor this year.

2) chromed cleats and rail fasteners etc. This boat was once in salt water so all the hardware is pitted. I really do not want to replace all of it if I do not have to since I am on a budget. Anyone try sanding and then spray painting the hardware? I have seen some shiny silver spray paint at the store anyone ever try this as a cheap fix? I am sure that it will not look as nice as chrome but is it worth a try?

I will take some pictures this weekend to show the progress we have made in the last two weeks. It is slow going when you are stripping off 6 layers of bottom paint while the boat is on the trailer.

Thanks!

 

[tashasdaddy]

Re: Can You Sand Aluminum?

yes you can sand it with like 400grit, besure to prime it, before painting.

 

[iwombat]

Re: Can You Sand Aluminum?

For your pitted cleats and rails.

Just how pitted? If the pits are minor, there are some little tricks to make them disappear.

If they're big and you need to paint, rough them up real good with course sandpaper before priming and painting. That chrome paint you can get is fairly disappointing. My suggestion is get some hammered finish metallic paint. It'll clean up any surface imperfections and keep the same color.

 

[Yacht Dr.]

Re: Can You Sand Aluminum?

wire wheel your rivets and existing hart to get painted areas till bare alum.

Must .. Alumeprep and Alodine your exposed Alum. area then PRIME with zinc kromate ( cromate ) .. sand to 320 ( not breaking through primer or spot prime again with a pre-val type sprayer )

as for your first question..you can sand 180 grit on alum.
but Totaly Blow the surface before you wipe down. ( or Vacuum thoroughly )

GL M8.

 

[Bob_VT]

Re: Can You Sand Aluminum?

I am almost positive that I read never to use a wire wheel on the aluminum boat. I seem to remember that the wire wheel can chew up aluminum and do more damage and I also recall that wire wheeling aluminum is a sure way to promote galvanic reaction and corrosion.

You do need to get a handle on the corrosion that you have or it is like cancer to the boat.

 

[tommays]

Re: Can You Sand Aluminum?

If you use a steel wire wheel on stainless or aluminum it will have rust marks till you sand out the metal bits

I finish SS for food tanks and you really have to be carefull with what you use to finish metal

We use a LOT of scotch brite pads as there non metal and will remove any stain or lose paint while takeing very littel of the base metal


Tommays

 

[i386]

Re: Can You Sand Aluminum?

I doubt paint will stay on cleats if you use them.

 

[Yacht Dr.]

Re: Can You Sand Aluminum?

yes you can sand it with like 400grit, besure to prime it, before painting.

have you ever sanded hardware with 400g ? and what primer have you ever heard of that suggests 400g sanding promotion before application ????

gazelle wants a leak prob fixed from inside..mebbe outside..ive never heard of wire wheeling promoting gavinitic,magnetic or othwise detramental fowlacies if it is cleaned and washed proporly. as i said..alumiprep and alodine..then zinc Chromate ! sand .. reprime all burns...tell me that it wont work...again..and tell poor gazelle to hand or wet sand around rivets with 400 grit is the WAY to go ... ok..best case drill out all rivs , clean, re-rivet, with aluminium rivets that are zinc washed and then thin beed of zink in a stick.. my god 10k later Mr. G will have a proper boat now..

Sorry If I offended anyone here..

YD

 

[Bondo]

Re: Can You Sand Aluminum?

The Issue with Wire Wheeling Aluminum, is the Same Issue I deal with when Welding the stuff,...
You Have to use a SSteel Brush, or there'll be Carbon Steel Contamination......
Which will lead to Rust spots,+ other Issues.......

I Caution Against Sanding the Hull,+ trying to chase the tiny Pits,+ other bits of old paint,.....
That hull is probably Only about .030" thick,.....
It doesn't take very much Sanding,+ you'll have Extremely Thin spots in the Hull.......

Get the Best Possible surface with a Light Sanding,+/or use of a SSteel Wire Wheel,......
Then Prime,+ Paint it........

It's a Boat Hull,...... Not a Show Car...........

 

[Bob_VT]

Re: Can You Sand Aluminum?

My point was that a wire brush will eat aluminum FAST. It might be too aggressive.

Hey Yacht Dr. I am one who will admit I do not know everything... "with aluminium rivets that are zinc washed and then thin beed of zink in a stick" Where would one get "zink washed" rivets and "zinc in a stick" ? A link to a source would be nice.

 

[Yacht Dr.]

Re: Can You Sand Aluminum?

Im just saying ..for speed and cost sanding with 180 grit and wire wheeling ( which I didnt mention was brass ) is in MHO the best way to go.

I did this aluminium boat with a 6" porter cable DA..180 grit .. 4" angle grinder with a brass brush to remove all corrotion around rivets and plates. of course I drilled out and re-riveted all loose rivets or possible failing rivets..washed and did as i described as above post.

I also used paint stripper around more hard to get areas along with a small thoothbrush style wire brush..

no leaks.. now after a season..or 2 you might find a leak on some rivs..you replace them as you go..

and Im sure the boat is not 5 hundreths of an inch thick..more like 1/8 th

 

[ztim]

Re: Can You Sand Aluminum?

The boat's skin has a very thin pure aluminum coat over the alloy aluminum. I would not use anything stronger than scotch brite. Aluminum rivets such as AD aircraft type can be found on the net. Alodine is easy and will save much work down the line. A coat of zinc chromate and paint should work. As it was said, it is not a show car.

 

[tashasdaddy]

Re: Can You Sand Aluminum?

i have to say. reading this post i wanted to puke. who is this Seaman Yacht Dr. i've been her quite a while and never heard of him. we've been a friendly group and i know better attitudes don't get you far here. i don't know everything but i guess if you a Yacht Dr., you do.

 

[Bob_VT]

Re: Can You Sand Aluminum?

Gazelle..... just a bit of advice and a warning..... DO NOT use an angle grinder with any wire brush on the aluminum boat. It has far too much power and if it catches it will go right through the hull.

Yes you can get closed end pop rivets on the net. You need to know the proper length. The length will vary depending on what is "unseen" on the other side. If you have a leak and need to replace a rivet or tighten it up there are a few proven methods used here.

You can purchase a small (the smallest) bottle of marine tex and coat the rivet before you pop it and that will help with a seal..... so will coating the rivet with 3m 5200.

Take our proven advice and stay clear of an angle grinder on the aluminum hull. Most riveted aluminum hulls are .072" (and not the .125 1/8") which is closer to a 1/13th of an inch used on welded hulls.

Most of the old timers here will tell you the best method for leaks is from the inside. 3m 5200 will adhere to a rivet from the outside and if it is a trailered rig .... a temporary repair with 5200 will last.

 

[iwombat]

Re: Can You Sand Aluminum?

I recently got a bag of 200 closed end aluminum blind rivets for a hull repair for $25 (minimum order). They worked great and I didn't need a partner to get it all done. I sealed it all up with gluvit inside and out and it holds water out just fine now.

The clean up was done with plain 'ol elbow grease and one of the scotch-brite pads with a handle.

 

[gazelle]

Re: Can You Sand Aluminum?

Thanks for the info everyone.

I had to go on the road for work so I have not worked on the boat in two weeks. I plan on finishing the stripping this weekend.

Should I put something on the corrosion areas or is paint enough? I have used rust converter on steel in the past, is there something similar for AL?

I will probably just lightly sand the current areas by hand to try and remove all corrosion unless I hear of a better solution. Is there a way to stop the corrosion? I have zinc on the boat but I guess this is not enough. I was under the impression that the zinc would stop all corrosion. It actually looks like the corrosion may be progressing as it sits on the trailer since there are some white drip like areas coming off the boat. It is not puddling below but it looks similar to a drop of water coming off the boat. It is white and chalky so I assume it is corrosion.


When I finish stripping I will go through the proper procedures for prep and paint.

 

[Yacht Dr.]

Re: Can You Sand Aluminum?

alumiprep and alodine..then zinc Chromate

yd

 

[mikesea]

Re: Can You Sand Aluminum?

you might want to brush some paint stripper on and then use the scotch pad to remove the stubborn spects.It doesnt take as long as you may think. I worked at an airplane oaint shop and thats the way I did it on the planes.And be sure to follow Yacht Dr.prep instructions. Alum is a funny metal.As for the coating the rivets,maybe you can use some 5200 adhesive and brush it over the rivets,since alum flexes alot,i would think something elastic should be used.There is an alum.sealent sold for mobile home roofs,you might consider it,sold at camper stores.

 

[Scaaty]

Re: Can You Sand Aluminum?

Scothbrite pads are the way to go. They come in HUNDREDS of grits, sizes. Google Grainger..pages of the right stuff