Cast Aluminum Windlass Cover

[Islandmike]

I am rebuilding my Simpson Lawerence Seatiger Windlass and just had the housing sandblasted. It is cast aluminum, what type of paint or primers would be best to put on now that it is down to bare aluminum? Any help would be greatly appreciated.

[Pblais]

Pre treatment of cast aluminum is really the trick to getting paint to realy stick. I'm sorry I don't have a detailed recipie but cast aluminum is harder to paint than most other types. I would hope you could totally disassemble it before you did anything. It needs to be chemically treated before you can primer.

Here is a good link I found:

1318 How to paint aluminum (October 22)

You really can't just wash and prime.

[Alan Wheeler]

You need to start with an etch primer. There are several available. Make sure you give the alloy a good clean. I know it is clean from the SBlast, but the oxide forms quickly. So give a rub over with a scotchbrite and some detergent to ensure it has no oil spots contaminating the surface. The etch primer MUST coat the entire surface to ensure a good long lasting bond. I suggest going with an epoxy system. This can be obtained in both one and two pot systems. Two pot is the harder, but slightly more difficult to apply. Two pot etch primer will need to be used along with two pot undercoats.
Single pot epoxies and etch primers are available in spray cans. It is still a good wearing product and is much easier to apply.
Or you could send the housing away and have it powder coated.
it results in a good hard wearing finish that will last many years, but when it does eventually fail, it tends to become a real mess.

[Islandmike]

Thank you for your help, this is going to be a little more difficult than I had first thought. In fact this whole project has been a little more extensive than I orginally thought. I have had to have things fabricated, parts ordered from Scotland that was held up at Customs and now not even an easy paint job. I hope this windlass will be everything I have read about it. By the time I am done with this it will have cost me in the neighborhood of $600.00 US. But I still think it will be worth it, again thanks for your advice and help, as usual I can count on this board to give me lots of help.

[Steve Pope]

You could consider having it annodised, I have a Lofrans Tigre that had the paint coming off so I had it blasted and annodised, it came out a dark grey colour. looks OK to me.

[Islandmike]

what does that mean annodised? Hate to sound ignorant, but not sure what that is?

[Steve Pope]

It is a treatment of aluminium that gives it a very good protection against salt water. It is used on many / most alluminium nautical fittings, masts, booms, blocks, cleats etc. etc.

[Alan Wheeler]

Clear annodising should come out the shiney Aluminium colour. For it to be grey means that the process has had a grey dye added.
The depth of the annodised surface is due to the time the part has been in the process for. If the annodised surface is not deep, it is subject to scratches that in turn lead to corrosion again.
Still, it is a very hard wearing finish.

[Steve Pope]

Sorry Alan, no grey dye, it just came out that way. The annodisersaid that I should expect it to come out the way it has. An older casting perhaps?

[Whimsical]

The more silicon in the alloy the darker the grey colour when anodising. Marine grade alloy plate, say 5083, come out a light to mid grey.
Only pure ally will be silver.
Mike

[Jentine]

Your best bet is to take the housing to a shop that does powder coating. I am sure the manufacturer did that originally and it lasted years.

[Benjamaphone]

We clear-coat annodize all of our cast aluminum-magnesium products. Annodized castings are much more resistant to damage than painted ones. The problem comes up when/if you need to re-annodize because the magnesium gets eaten up during the reaction process. This limits the number of times it can be done to 1 or 2 before the finish becomes less than desirable. If there are any questions about annodized aluminum I should able to help out.