paint advice needed for me , a total paint newbee.

hi,
i found this group through googling for info on tekaloid paint.
im painting my 90 rebuild and i have ordered some tekaloid coach enamel
from a supplier whoem i got in touch with through stephen hull's
painting tips site.

im going to start with the bulkhead (new) and as its made out of steel
and not aluminium i thought id use some red oxide primer.

my first question is , can i paint caladonian blue tekaloid synthetic
coach enamel over hammerite red oxide primer?

and my second question is , my 90 has been repainted/sprayed in the
past and i dont know what kind of paint has been used so will i have to
totally strip it down to bare aluminium to repaint it?
i really dont want to paint over the old paint only to have it reacting
with the tekaloid.

any advice would be great and much appreciated guys.

cheers,

Rob.

In message <[email protected]>
"nobber" <[email protected]> wrote:

>hi,
>i found this group through googling for info on tekaloid paint.
>im painting my 90 rebuild and i have ordered some tekaloid coach enamel
>from a supplier whoem i got in touch with through stephen hull's
>painting tips site.
>
>im going to start with the bulkhead (new) and as its made out of steel
>and not aluminium i thought id use some red oxide primer.
>
>my first question is , can i paint caladonian blue tekaloid synthetic
>coach enamel over hammerite red oxide primer?

You can paint over Hammerite with any synthetic but it would be more
compatible if you paint in a synthetic primer and bin the Hammerite.

>and my second question is , my 90 has been repainted/sprayed in the
>past and i dont know what kind of paint has been used so will i have to
>totally strip it down to bare aluminium to repaint it?
>i really dont want to paint over the old paint only to have it reacting
>with the tekaloid.

You don't have to strip all the paint off, only remove lose or flaking
paint and provide a key by rubbing it down.
Synthetic paint will NOT react when painted on top of any existing paint
finish but it WILL react if other non-synthetic paints are applied over
the top of it, like Hammerite.

Have a look at this data sheet:
http://www.stephen.hull.btinternet.co.uk/data.html you'll find Tekaloid
do a nice Alkyd "Red Oxide" (BA74 R01) synthetic primer and you can save
the Hammerite for railing, drainpipes etc.

Steve.


--
http://www.stephen.hull.btinternet.co.uk
Coach painting tips and techniques + Land Rover colour codes
Using a British RISC Operating System 100% immune to any Windows virus.
"Whatever is rightly done, however humble, is noble". Henry Royce

thanks for the info steve. unfortuantly i have to use the hammerite as
im already behind on this and im pressing to get it done (the rebuild)
before christmass so waiting on a delivery (can only be done on
saturday) will set me back another week and the rebuild is pretty much
waiting on the bulkhead being installed.
as its only the bulkhead , most of which is hidden it shouldent be to
much of a problem if the finish isent up to scratch.
im still in two minds though with stripping the vehicle with nitromores
before painting , the rear tub is pretty badly scratched and the bonnet
has been partly painted with what looks to have been an old rag. all
three doors will be new as will the seat box so all i will have to
strip is the tub , bonnet and sides (window'd) and the two wings.
i understand i will need an etch primer but will the bare aluminium
need prepped to accept the primer in any way?

also , after painting im storing the panels in my shed , would keeping
a heater on in there help the paint to harden?

thanks for the info steve. unfortuantly i have to use the hammerite as
im already behind on this and im pressing to get it done (the rebuild)
before christmass so waiting on a delivery (can only be done on
saturday) will set me back another week and the rebuild is pretty much
waiting on the bulkhead being installed.
as its only the bulkhead , most of which is hidden it shouldent be to
much of a problem if the finish isent up to scratch.
im still in two minds though with stripping the vehicle with nitromores
before painting , the rear tub is pretty badly scratched and the bonnet
has been partly painted with what looks to have been an old rag. all
three doors will be new as will the seat box so all i will have to
strip is the tub , bonnet and sides (window'd) and the two wings.
i understand i will need an etch primer but will the bare aluminium
need prepped to accept the primer in any way?

also , after painting im storing the panels in my shed , would keeping
a heater on in there help the paint to harden?

On 28 Oct 2006 06:28:57 -0700, "nobber" <[email protected]>
wrote:

>
>thanks for the info steve. unfortuantly i have to use the hammerite as
>im already behind on this and im pressing to get it done (the rebuild)
>before christmass so waiting on a delivery (can only be done on
>saturday) will set me back another week and the rebuild is pretty much
>waiting on the bulkhead being installed.
>as its only the bulkhead , most of which is hidden it shouldent be to
>much of a problem if the finish isent up to scratch.
>im still in two minds though with stripping the vehicle with nitromores
>before painting , the rear tub is pretty badly scratched and the bonnet
>has been partly painted with what looks to have been an old rag. all
>three doors will be new as will the seat box so all i will have to
>strip is the tub , bonnet and sides (window'd) and the two wings.
>i understand i will need an etch primer but will the bare aluminium
>need prepped to accept the primer in any way?

when i did the 101, the instructions on the etch primer said to key
the surface before painting it. I think i went over it with some
coarse wet and dry before spraying it with the etch primer.

if it doesnt have much paint on then go ahead with the nitromors. if
it has a lot of paint on (like 10 layers of military paint then it can
take years!)

>also , after painting im storing the panels in my shed , would keeping
>a heater on in there help the paint to harden?

just bring them into the house for a bit (says he with a living
room full of wires and dashboards...)

In message <[email protected]>
"nobber" <[email protected]> wrote:

>
>thanks for the info steve. unfortuantly i have to use the hammerite as
>im already behind on this and im pressing to get it done (the rebuild)
>before christmass so waiting on a delivery (can only be done on
>saturday) will set me back another week and the rebuild is pretty much
>waiting on the bulkhead being installed.

>as its only the bulkhead , most of which is hidden it shouldent be to
>much of a problem if the finish isent up to scratch.
>im still in two minds though with stripping the vehicle with nitromores
>before painting , the rear tub is pretty badly scratched and the bonnet

If the paint is particulary bad then you could strip it although this is
time consuming, expensive and messy, or you could use an electric/air
sander to remove all the paint defects more efficiently.

>has been partly painted with what looks to have been an old rag. all
>three doors will be new as will the seat box so all i will have to
>strip is the tub , bonnet and sides (window'd) and the two wings.
>i understand i will need an etch primer but will the bare aluminium
>need prepped to accept the primer in any way?

Acid etch is required to give your primer something to bite into because
Aluminium (birmabrite) is a natural oily metal which has very little
adhesion quality. You can use a scotch-cloth (medium grade) to scuff
over the bare alluminium which will provide a key for the etch primer.

>also , after painting im storing the panels in my shed , would keeping
>a heater on in there help the paint to harden?

It wont make that much difference, heat will only help it dry quicker,
air flow and light will help harden the synthetic.

Steve.


--
http://www.stephen.hull.btinternet.co.uk
Coach painting tips and techniques + Land Rover colour codes
Using a British RISC Operating System 100% immune to any Windows virus.
"Whatever is rightly done, however humble, is noble". Henry Royce

Stephen Hull wrote:

> Acid etch is required to give your primer something to bite into because
> Aluminium (birmabrite) is a natural oily metal which has very little
> adhesion quality. You can use a scotch-cloth (medium grade) to scuff
> over the bare alluminium which will provide a key for the etch primer.

Isn't it because the oxide on aluminium is a slippery bugger, since the
oxide is a very hard ceramic.

I've never seen any metal described as "naturally oily" before

Steve

In message <[email protected]>
Steve Taylor <[email protected]> wrote:

>Stephen Hull wrote:
>
>> Acid etch is required to give your primer something to bite into because
>> Aluminium (birmabrite) is a natural oily metal which has very little
>> adhesion quality. You can use a scotch-cloth (medium grade) to scuff
>> over the bare alluminium which will provide a key for the etch primer.
>
>Isn't it because the oxide on aluminium is a slippery bugger, since the
>oxide is a very hard ceramic.
>
>I've never seen any metal described as "naturally oily" before
>
>Steve

The oxidisation or ceramic as you call it is a natural process.

Aluminium is classed as a reactive metal and like iron it reacts with
oxygen causing surface corrosion. Aluminium left in its bare metal state
corrodes producing ”aluminium oxide• which is a form of corrosion that
will completely cover the surface and yet protects it from further
corrosion. This white aluminium oxide powder formed on bare aluminium
can be scraped off, which will lead to further corrosion because the
oxide is naturally weak having little or no strength.

This process is called anodising.

However anodising aluminium, by an electro chemical process for example,
physically alters the metal surface and produces a really tough dense
layer of oxide offering maximum protection to bare aluminium that does
NOT need painting.

Without the anodising process aluminium remains oily.

Steve.


--
http://www.stephen.hull.btinternet.co.uk
Coach painting tips and techniques + Land Rover colour codes
Using a British RISC Operating System 100% immune to any Windows virus.
"Whatever is rightly done, however humble, is noble". Henry Royce

Thanks guys , i appreciate the advice.
you can follow my progress here if you like.

http://bluelandrover90rebuild.blogspot.com/

its slow going at the moment but it will pick up soon.

cheers,
Rob.
Stephen Hull wrote:
> In message <[email protected]>
> Steve Taylor <[email protected]> wrote:
>
> >Stephen Hull wrote:
> >
> >> Acid etch is required to give your primer something to bite into because
> >> Aluminium (birmabrite) is a natural oily metal which has very little
> >> adhesion quality. You can use a scotch-cloth (medium grade) to scuff
> >> over the bare alluminium which will provide a key for the etch primer.
> >
> >Isn't it because the oxide on aluminium is a slippery bugger, since the
> >oxide is a very hard ceramic.
> >
> >I've never seen any metal described as "naturally oily" before
> >
> >Steve
>
> The oxidisation or ceramic as you call it is a natural process.
>
> Aluminium is classed as a reactive metal and like iron it reacts with
> oxygen causing surface corrosion. Aluminium left in its bare metal state
> corrodes producing "aluminium oxide· which is a form of corrosion that
> will completely cover the surface and yet protects it from further
> corrosion. This white aluminium oxide powder formed on bare aluminium
> can be scraped off, which will lead to further corrosion because the
> oxide is naturally weak having little or no strength.
>
> This process is called anodising.
>
> However anodising aluminium, by an electro chemical process for example,
> physically alters the metal surface and produces a really tough dense
> layer of oxide offering maximum protection to bare aluminium that does
> NOT need painting.
>
> Without the anodising process aluminium remains oily.
>
> Steve.
>
>
> --
> http://www.stephen.hull.btinternet.co.uk
> Coach painting tips and techniques + Land Rover colour codes
> Using a British RISC Operating System 100% immune to any Windows virus.
> "Whatever is rightly done, however humble, is noble". Henry Royce

Stephen Hull wrote:
This white aluminium oxide powder formed on bare aluminium
> can be scraped off, which will lead to further corrosion because the
> oxide is naturally weak having little or no strength.

I've a feeling that´s actually aluminium hydroxide ( Al(OH)3 ), not
aluminium oxide (Al2O3), its not actually strongly bonded at all.
Aluminium oxide is clear as far as I can remember. Out of interest,
undoped Alumina is the gemstone corundum. Doped, it becomes "sapphire"
(add titanium) or "Ruby" (add chromium). Alumina IS a "ceramic".

> This process is called anodising.

No, that white stuff is purely a corrosion product. Its anodising when
its grown on the surface electrically, usually in a sulphuric acid
process, sometimes in a chromic acid process. Its anodising because the
job forms the positive electrode of the cell.

> Without the anodising process aluminium remains oily.

What is "oily" ? do you mean "non-stick¨ ? Oily to me would imply it has
lubrificity, and it doesn´t, aluminium seizes and galls very easily in
screws, and anything you accidentally stick together before you get the
clearances right.


Steve

I know it's off topic but there seem to be knowledgeable people here, what's
the green coating often seen on alloy parts inside aircraft to prevent
corrosion, which seems to work pretty well, is it some sort of anodising?.
Greg

Greg wrote:
> I know it's off topic but there seem to be knowledgeable people here, what's
> the green coating often seen on alloy parts inside aircraft to prevent
> corrosion, which seems to work pretty well, is it some sort of anodising?.
> Greg
>
>
I think thats a chromate passivation, and its done by immersion in a
really nasty mixture of phosphoric acid, hydrofluoric and chromic acid,
but since it needs hexavalent chromium you ain't going to see that in
Europe anymore , under RoHS regulations.

Steve

"Greg" <[email protected]> wrote in message
news:[email protected]...
>I know it's off topic but there seem to be knowledgeable people here,
>what's
> the green coating often seen on alloy parts inside aircraft to prevent
> corrosion, which seems to work pretty well, is it some sort of anodising?.
> Greg
>
>

Probably a process known as Alocrom, which is a chromate conversion. There
are several different types available. I think it is Alocrom 1000 that
produces the greenish tint. 1200 is more of a gold colour.

I think there is a bit of a debate at the moment about the legality of 1000
due to the emission of hexavalent chromium being at about the EU limit.

Regards
Jeff

Jeff wrote:

> Probably a process known as Alocrom, which is a chromate conversion. There
> are several different types available. I think it is Alocrom 1000 that
> produces the greenish tint. 1200 is more of a gold colour.
>
> I think there is a bit of a debate at the moment about the legality of 1000
> due to the emission of hexavalent chromium being at about the EU limit.

We used Alocrom a lot at the last place I worked but it was golden, I
didn't reaslise there were variations. It was of very variable quality,
sometimes it would wipe off on your hands!, but I put that down to crap
suppliers.

Greg

In message <[email protected]>
Steve Taylor <[email protected]> wrote:

>I've a feeling that´s actually aluminium hydroxide ( Al(OH)3 ), not
>aluminium oxide (Al2O3), its not actually strongly bonded at all.
>Aluminium oxide is clear as far as I can remember. Out of interest,
>undoped Alumina is the gemstone corundum. Doped, it becomes "sapphire"
>(add titanium) or "Ruby" (add chromium). Alumina IS a "ceramic".

>> This process is called anodising.
>
>No, that white stuff is purely a corrosion product. Its anodising when
>its grown on the surface electrically, usually in a sulphuric acid
>process, sometimes in a chromic acid process. Its anodising because the
>job forms the positive electrode of the cell.

I agree, although I was only generalising but the corrosion product
acts as a form of natural anodising that helps protect the bare alloy
yet its not really anodised in the true sense of the word.
Aluminium is also classed as a reactive metal and you would expect bare
aluminium to corrode quicker than it actually does yet it does not
because the formation of this white powdery aluminium oxide on the
surface protects the metal to some degree as a sort of anodisation but
it is very weak.

IIRC electro-chemical anodising is a process which creates a tough dense
hydroxide layer that resists abrasions and helps protect the aluminium
underneath. The chemicals involved in anodising are indeed Sulphuric
acid, Sodium Hydroxide and Sodium Sulphate.

>> Without the anodising process aluminium remains oily.
>
>What is "oily" ? do you mean "non-stick¨ ? Oily to me would imply it has
>lubrificity, and it doesn´t, aluminium seizes and galls very easily in
>screws, and anything you accidentally stick together before you get the
>clearances right.

IKWYM, cutting through a Land Rover body for example is extremely
difficult, almost impossible with a hacksaw.

I'm not qualified to comment on the chemistry of aluminium only paint
(allegedly) and from a painters point of view, bare aluminium is
described as an oily metal in terms of paint adhesion which is where
acid etching comes into play by getting a paint substrate to stick to
it.

Regards,

Steve.


--
http://www.stephen.hull.btinternet.co.uk
Coach painting tips and techniques + Land Rover colour codes
Using a British RISC Operating System 100% immune to any Windows virus.
"Whatever is rightly done, however humble, is noble". Henry Royce

Stephen Hull wrote:
>
> IIRC electro-chemical anodising is a process which creates a tough dense
> hydroxide layer that resists abrasions and helps protect the aluminium
> underneath. The chemicals involved in anodising are indeed Sulphuric
> acid, Sodium Hydroxide and Sodium Sulphate.
There is really only electrochemistry going on. The sodium hydroxide is
used to etch a nice surface on the metal before you start, the Sulphuric
acid provides a conductive path for the electricity during the anodise,
and I don´t recognise sodium sulphate as part of the process. Oxygen is
released at the anode terminal of the system (ie the job) and that´s
what makes the oxide of course.

Its actually very easy to anodise things, if you feel like having a go.
I did some small parts at work this week, and dyed them a fetching deep
black. Once the part is boiled, the resulting coat is VERY tough (and
its the hydrated form, as you say)
>
> IKWYM, cutting through a Land Rover body for example is extremely
> difficult, almost impossible with a hacksaw.
Thats because its almost fully annealed isn´t it ? So soft it sticks
very well to your saw.

Steve

Hi,
I used to work in a plant making aircraft parts that had it's own process shop. -AP Hydraulics / Lockheeds.
Al alloy parts were first vapour degreased and anodised as above. When the pores in the metal were open they look like hexagonal crystal with a hole in the centre. The parts were then diped in a hot vat of dye to colour them. The green is a nato standardised colouring. From this, they were then boiled in a solution to seal the dye.
I remember allochrom being a brushable coating method, as parts often needed rework, and this produced a golden yellow.
For steel parts, we were still cad plating bolts, but tin/zinc was starting to be specified more ofted. The addition of tin to the coating made it slightly less reactive, plus this was usually passivated (clear coating) or chromate passivated (golden coating) as seen on most woodscrews thesedays.
It was a surprisingly dangerous place always leaving a metallic taste in your mouth from the cyanide hardening pots - which were red hot boiling potassium cyanide salt, and the orange fumes from the chromium tanks. I was always surprised to see the mice running about under the duckboards there and wondered how they survived! Amyl Nitrite was kept at various points as an antidote to the cyanide.