Drop-out paint question

[Bill]

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

 

[Jim Higson]

Bill wrote:

> 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.

 

[catzz66]

Jim Higson wrote:
>
>
> 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.

 

[Jay Beattie]

"catzz66" <[email protected]> wrote in message
news:[email protected]...
> Jim Higson wrote:
> >
> >
> > 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.

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.

 

[Bill]

"Jay Beattie" <[email protected]> wrote in message
news:[email protected]...
>
> "catzz66" <[email protected]> wrote in message
> news:[email protected]...
> > Jim Higson wrote:
> > >
> > >
> > > 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.
> > >

>
> 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

 

[Patrick Lamb]

On Fri, 09 Feb 2007 02:30:10 GMT, "Bill" <[email protected]> wrote:
>"Jay Beattie" <[email protected]> wrote in message
>news:[email protected]...
>> 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.

>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.

 

[Grolch]

>
>>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 protected]
______________________

 

[autopi]

On Feb 7, 5:58 pm, "Bill" <[email protected]> wrote:
> 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.

 

[[email protected]]

On Feb 9, 1:24 am, "autopi" <[email protected]> wrote:
> On Feb 7, 5:58 pm, "Bill" <[email protected]> wrote:
>
> > 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.

 

[catzz66]

Bill wrote:
>
>
> 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.

 

[Bill]

<[email protected]> wrote in message
news:[email protected]...
> On Feb 9, 1:24 am, "autopi" <[email protected]> wrote:
> > On Feb 7, 5:58 pm, "Bill" <[email protected]> wrote:
> >
> > > 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.
>
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

 

[Bill]

"Grolch" <[email protected]> wrote in message
news:x2Tyh.38203$Oa.31443@edtnps82...
>
> >
> >>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 protected]
> ______________________
>
Thanks for the thoughtful response. I'm going for the polyurethane modeling
paint.
Bill