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Join Date: Jun 2011
Location: West Vancouver B.C.
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Considering your situation - small spar, first time etc. - I'd go with a one part poly. Strip the spar to the tube. Abrade it with "scrubber" disks for an angle grinder. These are available at auto body shops and tool stores. They look like resinated pot scrubber material and are specifically for stripping finishes. After you are done with them, scrub the spar with Scotchbrite pads and you should be ready to start putting on finish coats.
By the way, this is one instance where I disagree with Faster - I don't feel it is necessary to strip off all the old anodizing - that is not a "coating" in the usual sense and won't peel or anything like that.
Immediately after the final abrasive pass, wipe it down with solvent and spray on Zinc Chromate primer - this is a tie coat that sticks to aluminium - practically the only thing that does - and must be done right away as Aluminium oxidizes extremely quickly.
Continue coating per the manufacturers directions for whatever finish you choose. I prefer to use semi-gloss or satin finish in low glare colours - I used black for mine which gave a finish like "trim black" used on window mouldings on cars and such - it helps to reduce glare on sunny days.
I, myself, personally intend to continue being outspoken and opinionated, intolerant of all fanatics, fools and ignoramuses, deeply suspicious of all those who have "found the answer" and on my bad days, downright rude.