I have a chunky cast aluminum frame that is part of some marine watersports
equipment.
(link if you want to see it)
http://i771.photobucket.com/albums/x...ngs/SkySki.jpg

It is the red seat frame that is the issue.


The 'paint' finish, has started flaking off in large pieces .. and aluminum
underneath has some fine white oxide.
this started at the through holes .........

Manufacturer advises this was powder coated ......... and obviously it is
not very good after 2 yrs salt water use.


End of boating season I need to strip the finish off and re-finish ....
manufacturer advised sandblasting & anodizing ......... however anodizing
usually needs a lot of Hrs on polishing first (read - expensive)
What options do I have ........
I could get the stuff sandblasted or chemically removed (might be kinder)
..........

Anybody experience with acid etch primers & suitable paint ? ..........
maybe even 2 part epoxy paint.

The item does not get any physical damage other than sal****er hitting it at
20mph when in use., it does get fully hosed down after each use.



Just an FYI ... the lower wings I had polished and anodized in red, and main
bar in black ... they are fine.

On Aug 23, 10:20*pm, "Rick Hughes"
wrote:
I have a chunky cast aluminum frame that is part of some marine watersports
equipment.
(link if you want to see it)http://i771.photobucket.com/albums/x...20n%20things/S...

It is the red seat frame that is the issue.

The 'paint' finish, has started flaking off in large pieces .. and aluminum
underneath has some fine white oxide.
this started at the through holes .........

Manufacturer advises this was powder coated ......... and obviously it is
not very good after 2 yrs salt water use.

End of boating season I need to strip the finish off * and re-finish .....
manufacturer advised sandblasting & anodizing ......... however anodizing
usually needs a lot of Hrs on polishing first (read - expensive)
What options do I have ........
I could get the stuff sandblasted or chemically removed (might be kinder)
.........

Anybody experience with acid etch primers & suitable paint ? ..........
maybe even 2 part epoxy paint.

The item does not get any physical damage other than sal****er hitting it at
20mph when in use., *it does get fully hosed down after each use.

Just an FYI ... the lower wings I had polished and anodized in red, and main
bar in black ... they are fine.

I've some limted experience with ali finishes, but not in a marine
environment. From what I've seen, nothing is fully durable but
anodising. You can anodise ali yourself, using clothes dye to colour
it.
http://groups.google.com/group/sci.e...7037778dfd9de#


NT

I've some limted experience with ali finishes, but not in a marine
environment. From what I've seen, nothing is fully durable but
anodising. You can anodise ali yourself, using clothes dye to colour
it.
http://groups.google.com/group/sci.e...7037778dfd9de#


I can get anodizing done locally ... the anodizing is cheap ... few pounds
... as they just add it to other work in same colour .... the cost is the
polishing, and it would not be possible - within reason to polish this as
surface will now have corrosion.


Wonder if I could get some etch primer, then re-powder coat ?

On Aug 23, 10:20*pm, "Rick Hughes"
wrote:

Manufacturer advises this was powder coated ......... and obviously it is
not very good after 2 yrs salt water use.

Powder coat sucks. It's OK if a piece is perfect and untouched, but
any abrasion that goes through the coating just turns into a moist
pocket that spreads under the coating.

I'd expect to use an etch primer and re-paint it myself, but I'd look
for product advice from boat people, not landlubbers.

Anodising isn't a great finish for marine use. There's a lot of
variation in anodising, between hard and soft anodises and in the
basic quality of the work. Although I can anodise here (and in colour
too, which is easy, even splash anodising) I wouldn't expect to do a
good enough job to stand up to the marine environment. If you want to
try it though, talk to Caswell about DIY kits. Their nickel plating is
great stuff, if you're trying to do steel or brass.

Andy Dingley wrote:
On Aug 23, 10:20 pm, "Rick Hughes"
wrote:

Manufacturer advises this was powder coated ......... and obviously it is
not very good after 2 yrs salt water use.

Powder coat sucks. It's OK if a piece is perfect and untouched, but
any abrasion that goes through the coating just turns into a moist
pocket that spreads under the coating.


+1

I'd expect to use an etch primer and re-paint it myself, but I'd look
for product advice from boat people, not landlubbers.

+1

Anodising isn't a great finish for marine use. There's a lot of
variation in anodising, between hard and soft anodises and in the
basic quality of the work. Although I can anodise here (and in colour
too, which is easy, even splash anodising) I wouldn't expect to do a
good enough job to stand up to the marine environment. If you want to
try it though, talk to Caswell about DIY kits. Their nickel plating is
great stuff, if you're trying to do steel or brass.

Al. is poor material for marine use, full stop.

Id got for an epoxy paint as thick as possible..the cold non spraryed
equivalent of powder coating. The anodising is simply a way to build a
slightly thicker oxide layer, but oxide layers tend to be useless once
scratched and in any case don't take well to salty spray. Regard
anodising as a way to prep for coating - or as you say an etch primer.
Or would epoxy type paint key to a simple sanded type surface?

I think if I had to use Al. on a sea going boat, I'd be off to a yachty
place and looking for a tough expensive two pack paint...and some advice
on how to prep the surface..

On Aug 23, 10:20*pm, "Rick Hughes"
wrote:
End of boating season I need to strip the finish off * and re-finish .....
manufacturer advised sandblasting & anodizing ......... however anodizing
usually needs a lot of Hrs on polishing first (read - expensive)

Angle grinder!

Having now looked at the photo, this seems like a simple enough shape
that you can polish it yourself. Anodisers will take this, at much
less cost, if it's already polished or part-polished. You need an
angle grinder and a few paint stripping disks (they look like plastic
scourers). These ought to do it, although you _might_need a fine flap
wheel to start if the powder coat is particularly tough.

Once the aluminium is stripped clean, then polish it. Use an electric
drill and a range of wire brushes with abrasive-filled red nylon
bristles. These give a good polish on aluminium. There are also a
range of disks from 3M specially for stripping paint and polishing
aluminium. If you want a mirror finish (which isn't necessarily a good
idea) then finsih with 3M / Webrax scourer pads or else Garryflex
rubber blocks. Really though, take it to the plastic abrasive wheel
stage, then hand it over to the anodiser for final polishing (one
stage is cheap).

As for any polishing, it's not about the shine, it's about taking the
coarse scratches out. Don't move to a finer grit until you're really
done with the coarse stuff.

_Don't_ use steel tools, or tools you've also used on steel.

On 24/08/2011 11:31, Andy Dingley wrote:
Anodising isn't a great finish for marine use.

Any of you guys ever look at a boat's mast? 9 out of 10 are anodized
aluminium alloys. (the rest are either wood or synthetic composites
such as carbon/epoxy)

Andy

"Andy Champ" wrote in message
. uk...
On 24/08/2011 11:31, Andy Dingley wrote:
Anodising isn't a great finish for marine use.

Any of you guys ever look at a boat's mast? 9 out of 10 are anodized
aluminium alloys. (the rest are either wood or synthetic composites such
as carbon/epoxy)


My experience with anodizing is not good on red that is for sure, been
re-anodized twice, it fades to pink within 2 -3 weeks.
That is about 2 Hrs in salt water .. rest of time, rinsed, dried & kept out
of the sun.

"Rick Hughes" wrote in message
...

"Andy Dingley" wrote in message
...
On Aug 23, 10:20 pm, "Rick Hughes"
wrote:

Manufacturer advises this was powder coated ......... and obviously it is
not very good after 2 yrs salt water use.




An update ... from a Powder Coating specialist company ...
" It appears your item had Powder coat applied to insufficiently prepared
surface. We would do this by grit blasting with aluminum oxide to provide a
suitably abraded surface, then apply a suitable etch /primer baked on fully,
before being followed by the powder coated finish.

On Aug 24, 8:36*pm, Andy Champ wrote:
On 24/08/2011 11:31, Andy Dingley wrote:

Anodising isn't a great finish for marine use.

Any of you guys ever look at a boat's mast?

It's a great finish if it's done right, but this usually means careful
factory anodising immediately after extrusion of sections, where it's
a repeat process day-in day-out on the same sections and alloys. Post-
fabrication anodising by plating shops is a real crap-shoot for
quality and longevity.