Drop-out paint question

Bill said:

A lagre chunk of paint has chipped away from my rear drop-out.. Down to
the bare aluminum. Original is a high gloss black. What type of paint
should I use to touch it up. My concern is a little cosmetic, but more
importantly, I would like to prevent creeping oxidation under the adjacent
paint over time. Bill

IIRC, aluminium is quite reactive so alu oxide forms very quickly but this
isn't so bad because it isn't itself permiable to oxygen. I don't think
oxidation is a problem. Plenty of my bike parts (cranks, headsets etc) are
bare aluminium.

Besides, surely the paint has already come off on the bit where you clamp
the quick release or nuts?

I'd say black spray paint.

Jim Higson said:

IIRC, aluminium is quite reactive so alu oxide forms very quickly but this
isn't so bad because it isn't itself permiable to oxygen. I don't think
oxidation is a problem. Plenty of my bike parts (cranks, headsets etc) are
bare aluminium.

My second bike is an old 90s GT road frame. It is all aluminum and does
not appear to have any clear coat on it. The original poster is
probably worried about losing more paint than anything else, but
structurally I would not think that there'd be much to worry about based
on my bike.

"catzz66" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Jim Higson said:

IIRC, aluminium is quite reactive so alu oxide forms very

quickly but this

Quoted message said:

Quoted message said:

isn't so bad because it isn't itself permiable to oxygen. I

don't think

Quoted message said:

Quoted message said:

oxidation is a problem. Plenty of my bike parts (cranks,

headsets etc) are

Quoted message said:

Quoted message said:

bare aluminium.

My second bike is an old 90s GT road frame. It is all aluminum

and does

Quoted message said:

not appear to have any clear coat on it. The original poster

is

Quoted message said:

probably worried about losing more paint than anything else,

but

Quoted message said:

structurally I would not think that there'd be much to worry

about based

Quoted message said:

on my bike.

Not unless you live in a high salt environment like on the coast
or in one of those states that uses a lot of salt on the roads.
I have a number of aluminum frames with many chips that I ride in
the rain on a frequent basis with no serious oxidation. I see
plenty of bare Cannondale frames here in PDX with no serious
oxidation. -- Jay Beattie.

"Jay Beattie" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

"catzz66" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Jim Higson said:

IIRC, aluminium is quite reactive so alu oxide forms very

quickly but this

Quoted message said:

Quoted message said:

isn't so bad because it isn't itself permiable to oxygen. I

don't think

Quoted message said:

Quoted message said:

oxidation is a problem. Plenty of my bike parts (cranks,

headsets etc) are

Quoted message said:

Quoted message said:

bare aluminium.

Quoted message said:

Not unless you live in a high salt environment like on the coast
or in one of those states that uses a lot of salt on the roads.
I have a number of aluminum frames with many chips that I ride in
the rain on a frequent basis with no serious oxidation. I see
plenty of bare Cannondale frames here in PDX with no serious
oxidation. -- Jay Beattie.

I live in Ohio where there is plenty of salt on the roads and lots or
residue well into spring. My old Trek 2000 aluminum frameset is seriously
corroded in a number of places. Creeps in under the paint from scratches and
chips and causes it to bubble and flake.

Anyone have a suggestion as to how best to paint it rather than telling me I
don't need to paint it?

Original question:
"Original is a high gloss black, large chip down to bare aluminum. What type
of paint should I
use to touch it up. My concern is a little cosmetic, but more importantly, I
would like to prevent creeping oxidation under the adjacent paint over
time."

Bill

Bill said:

"Jay Beattie" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Not unless you live in a high salt environment like on the coast
or in one of those states that uses a lot of salt on the roads.
I have a number of aluminum frames with many chips that I ride in
the rain on a frequent basis with no serious oxidation. I see
plenty of bare Cannondale frames here in PDX with no serious
oxidation. -- Jay Beattie.

I live in Ohio where there is plenty of salt on the roads and lots or
residue well into spring. My old Trek 2000 aluminum frameset is seriously
corroded in a number of places. Creeps in under the paint from scratches and
chips and causes it to bubble and flake.

It's not the oxidation that's eating up your bike, really. It's the
chloride from your Ohio road salt that corrodes it. If it's really
gotten under the paint, you're going to need to sand everything down
to bare metal and repaint. And rinse it off frequently after that,
before the salt has time to react with the metal.

Quoted message said:

Anyone have a suggestion as to how best to paint it rather than telling me I
don't need to paint it?

Original question:
"Original is a high gloss black, large chip down to bare aluminum. What type
of paint should I
use to touch it up. My concern is a little cosmetic, but more importantly, I
would like to prevent creeping oxidation under the adjacent paint over
time."

Email address works as is.

Quoted message said:

Quoted message said:

Anyone have a suggestion as to how best to paint it rather than telling me
I
don't need to paint it?

Original question:
"Original is a high gloss black, large chip down to bare aluminum. What
type
of paint should I
use to touch it up. My concern is a little cosmetic, but more importantly,
I
would like to prevent creeping oxidation under the adjacent paint over
time."

Email address works as is.

Firstly I'd ask you what does the aluminum look like where it came off? Does
it look roughened?, cleaned? or is it shiny or oily? Look at the back off
the paint chip , if you have it. Notice anything? dirt, contaminants? What
about the edge of the chipped area. Can you chip more off fairly easily with
a knife. This might indicate a general problem with the coating or original
surface prep. So you could expect more pf same as time goes on. In that case
it may be worth considering a complete re-do like sandblast and powdercoat.
If everything looks sound and this spot is just spot damage here's what I
would do.

Ideally you should spot bead blast whatever area you need painted. One of
those glassware etching setups is enough for small spots and areas. Then use
modelling urethane in a matched colur. The slow drying kind. Paint it
several coats. The thickness of the total film build is what will prevent
the oxidation. The surface profile that you create preparing the surface is
what will keep it there. Keep the spots repairs tight to the damage, but
feather edges. Mask things. Use spray even. But make sure to build an
adequate overall film thickness over several (read at least three) coats.
Very good air movement and warmth. Don't try to get too thick on each coat,
that's worse (solvent entrapment, wrinkling). Move the masked spot slightly
larger each coat and feather a bit. The results should be pretty good.

Grolsch
--
______________________
HJ Wilke Consultants
NANAIMO
e-mail: [email hidden]
______________________

Bill said:

A lagre chunk of paint has chipped away from my rear drop-out.. Down to the
bare aluminum. Original is a high gloss black. What type of paint should I
use to touch it up. My concern is a little cosmetic, but more importantly, I
would like to prevent creeping oxidation under the adjacent paint over time.
Bill

I suppose it depends on how large a chip it is, but I'd use fingernail
polish. Suppose you could get auto touch up paint too, if you wanted
to get fancy.

autopi said:

Bill said:

A lagre chunk of paint has chipped away from my rear drop-out.. Down to the
bare aluminum. Original is a high gloss black. What type of paint should I
use to touch it up. My concern is a little cosmetic, but more importantly, I
would like to prevent creeping oxidation under the adjacent paint over time.
Bill

I suppose it depends on how large a chip it is, but I'd use fingernail
polish. Suppose you could get auto touch up paint too, if you wanted
to get fancy.

Vote number two for nail polish.. it even comes in black.. just find a
troubled teen to tell you where to get it.

Bill said:

Anyone have a suggestion as to how best to paint it rather than telling me I
don't need to paint it?

Not trying to be a wise guy, but it is not clear what is happening to
the aluminum, if anything. If it was steel and it was oxidizing, that
would be easier to understand. You're going to need to figure out what
is really going on, chemically, if you haven't already. Good luck.

<[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

autopi said:

Bill said:

A lagre chunk of paint has chipped away from my rear drop-out.. Down

to the

Quoted message said:

Quoted message said:

Quoted message said:

bare aluminum. Original is a high gloss black. What type of paint

should I

Quoted message said:

Quoted message said:

Quoted message said:

use to touch it up. My concern is a little cosmetic, but more

importantly, I

Quoted message said:

Quoted message said:

Quoted message said:

would like to prevent creeping oxidation under the adjacent paint over

time.

Quoted message said:

Quoted message said:

Quoted message said:

Bill

I suppose it depends on how large a chip it is, but I'd use fingernail
polish. Suppose you could get auto touch up paint too, if you wanted
to get fancy.

Vote number two for nail polish.. it even comes in black.. just find a
troubled teen to tell you where to get it.

Winter three years ago I stripped down my Serotta CSI and meticulously went
over it touching up and cleaning up. Got some strange looks when I walked
into the local drug store's fingernail polish department and started looking
for matching colors. The auto parts folks were more understanding.
Bill

"Grolch" <[email hidden]> wrote in message
news:x2Tyh.38203$Oa.31443@edtnps82...

Quoted message said:

Quoted message said:

Quoted message said:

Anyone have a suggestion as to how best to paint it rather than telling

me

Quoted message said:

Quoted message said:

Quoted message said:

I
don't need to paint it?

Original question:
"Original is a high gloss black, large chip down to bare aluminum. What
type
of paint should I
use to touch it up. My concern is a little cosmetic, but more

importantly,

Quoted message said:

Quoted message said:

Quoted message said:

I
would like to prevent creeping oxidation under the adjacent paint over
time."

Email address works as is.

Firstly I'd ask you what does the aluminum look like where it came off?

Does

Quoted message said:

it look roughened?, cleaned? or is it shiny or oily? Look at the back off
the paint chip , if you have it. Notice anything? dirt, contaminants? What
about the edge of the chipped area. Can you chip more off fairly easily

with

Quoted message said:

a knife. This might indicate a general problem with the coating or

original

Quoted message said:

surface prep. So you could expect more pf same as time goes on. In that

case

Quoted message said:

it may be worth considering a complete re-do like sandblast and

powdercoat.

Quoted message said:

If everything looks sound and this spot is just spot damage here's what I
would do.

Ideally you should spot bead blast whatever area you need painted. One of
those glassware etching setups is enough for small spots and areas. Then

use

Quoted message said:

modelling urethane in a matched colur. The slow drying kind. Paint it
several coats. The thickness of the total film build is what will prevent
the oxidation. The surface profile that you create preparing the surface

is

Quoted message said:

what will keep it there. Keep the spots repairs tight to the damage, but
feather edges. Mask things. Use spray even. But make sure to build an
adequate overall film thickness over several (read at least three) coats.
Very good air movement and warmth. Don't try to get too thick on each

coat,

Quoted message said:

that's worse (solvent entrapment, wrinkling). Move the masked spot

slightly

Quoted message said:

larger each coat and feather a bit. The results should be pretty good.

Grolsch
--
______________________
HJ Wilke Consultants
NANAIMO
e-mail: [email hidden]
______________________

Thanks for the thoughtful response. I'm going for the polyurethane modeling
paint.
Bill