I need to make a few intercooler hoses.
I built a bike for someone who made his own silicon hoses, he worked
for a company that made silicon hoses. The stuff the hoses were made
from was in sheet form. He wrapped a steel former, which I made I made
from bits of old handlebars, Then wacked it in the oven to cure.
Does anyone know what silicon to use, or where to get it?
If you're using it under-bonnet than the grade you need will be a
Flurosilicone compound, which is resistant to oils and greases, and as
it's for a hose you really need quite a high shore hardness grade if
you dont want it to collapse. Thats the easy bit answered.
However, you would need to buy it as sheet moulding compound (SMC) and
then crosslink (cure) it when its the right shape, and thats not so
simple. Effective cross-linking needs heat and pressure. Most SMC is
compression moulded in heated tools, or shapes like hoses with odd
paths are cured in an Autoclave, usually after being wrapped around a
former then completely enclosed in a deformable bag which is very
tightly 'vacuum wrapped' around the part before it is put in the
My knowledge on this is a bit limited though so you could try
contacting http://www.primasil.com/ or http://www.silicone.co.uk/ for
One final word of advice on safety, and this applies to all flouro
polymers and flouro rubbers. If this stuff burns and is then
extinguished with water don't ever touch it with bare hands. This
burning/extinguishing process produces Hydroflouric Acid for which
there is no known neutraliser. This stuff can get into your system very
easily from a skin burn, and apart from causing systemic poisoning and
death, the only way to prevent it spreading is amputation!
Unbelievably this stuff is also found in proprietary rust removers, and
is also a major hazard from burnt-out cars/bikes.
Hope his helps
Just had a quick peek at your website Richard. I see you're familar
with vacuum bagging from the CF work you did, so perhaps this won't be
such a problem after all!
Sorry for telling you stuff you already knew...
I don't know where you got this information Peter but I am afraid it is
sheer nonsense. Admittedly hydrofluoric acid is a strong acid and should be
treated with caution just the like sulphuric or hydrochloric acids. It also
has the unique ability to etch or even dissolve glass, but it can be
neutralised in exactly the same way as any other mineral acid. Neutralise it
with caustic soda for example and you get water and sodium fluoride, a
mineral that is a common ingredient of toothpaste and is added to drinking
water by some water companies to prevent tooth decay.
As for rust treatments, maybe you are thinking of phosphorous acid, which is
the only acid I know of in such formulations.
I think peter may mean an aluminium cleaner, the first aerosol wheel
cleaners had hydraflauric[yes i know i can't spell] acid in them.
The bloke who I saw make hoses worked for silfex or whoever it is that
make samco hoses. He didn't vacum the hose he wrapped it with what
looked like harness wrapping tape[ no adhesive].
"Chemical Information Overview
Hydrofluoric acid (HF) differs from other acids because the fluoride
ion readily penetrates the skin,
causing destruction of deep tissue layers, including bone. Pain
associated with exposure to solutions of
HF (1-50%) may be delayed for 1-24 hours. If HF is not rapidly
neutralized and the fluoride ion bound,
tissue destruction may continue for days and result in limb loss or
death. HF is similar to other acids in
that the initial extent of a burn depends on the concentration, the
temperature, and the duration of contact
with the acid."
You can NOT neutralise it once it is in your system. This is what I
meant I say. Make no mistake this is deadly stuff. Further down the
page on the same site it tells this story:
"HYDROFLUORIC ACID FATALITY TO LAB WORKER IN PERTH
Extract from Australian Institute of Occupational Hygienists
Newsletter, December 1994:
An accident in Perth highlighted just how hazardous this acid can be
and it is worth recounting for the
benefit of any lab working or hygienists whose work may involve
advising others who use this substance.
On November 12, a 37 year old man died in the Intensive Care Unit of
Fremantle Hospital after he
accidentally splashed about 100 ml of a 70% solution on his right leg
on October 28. It was estimated that
the extent of the spill covered about 10% of his total body area. The
individual was working as a
technician in a small paleontology laboratory, which was attached to a
private residence. HF is used in
the industry to digest silicates in ore samples. The victim immediately
attempted to remove the spill from
his clothing hosing himself down with a hose attached to a sink in the
laboratory. He then ran from the
laboratory to the swimming pool in the garden, and he remained in the
pool until the ambulance arrived
within the hour. At the time he appeared confused, possibly as a result
The following week his right leg was amputated, however despite this,
the individual eventually
succumbed to the toxic effects of the hydrofluoric acid 2 weeks after
the initial spill. There are a number of
points that need to be emphasized as a result of this, which are
relevant to all users of HF:"
Best to avoid the stuff altogether I think.
There are special neutralizing jellies to put on to the area after
contact with this stuff, but it has to be done immedialty or it won't
work (anyone using it would have this to hand before using it). I
remember some terrible occurances being reported several years ago
before the problems were widely known. Recovery workers and mechanics
dealing with burnt vehicles -some seals in vehicles contain this
compound- sustained very nast injuries, some resulting in amputation
of effected limbs.
This stuff should definately NOT be treated as other acids (and any
concentrated acid is pretty nasty!). Personally I wouldn't go
anywhere near it.
Rust remover for toilet fixtures sometimes contain dilute hydrofluoric
acid. The concentration is low enough it has the same warnings as any
other product containing a strong acid. I've spilt a drop or two on my
hands in the past with no negative effects.
Whenever hydrofluoric acid is mentioned in a forum like this there is
always someone who has read about its method of interaction with bone
after passing through the skin and they give the same hysterical
warnings. They don't seem to really understand that the interaction is
in the concentration. Seventy percent concentration is very dangerous.
One tenth of one percent is at worst an irritant. But then that goes
for any strong acid. Note the concentration before opening the bottle.
Another example glacial acetic acid can cause severe burns. Dilute
acetic acid is nice in salad dressing.
On Fri, 26 Aug 2005 14:35:18 +0100, "Cliff Coggin"
I've haven't read about it but I'll NEVER forget the scream from the
girl on the line where it was used in semiconductor etching at
Mullards factory by the Totton roundabout back in the late sixties
when she took off her glove and one finger stayed in it. That line was
in 'bay 5' iirc and I was in EOD in 'bay 8' - a long way away. They
were all supposed to do a pressure test on the gloves before putting
them on - the presumption was she didn't and there was a pin prick.
Fair point Kelley, and well made. I never meant this to be an
hysterical, I-know-more-than-you thing (and hopefully it hasn't been
taken that way), just a general warning for anyone who was unaware of
If in doubt, don't touch it:)
No, he is not.
If you replace the word "neutraliser" with "antidote" he is actually correct
(except I haven't come across it in rust removers either - that's usually
NaF (sodium fluoride) is okay in tiny doses - but it larger doses it is used
as rat poison.
It is extremely toxic to humans too. The acute oral rat LD-50 is 52 mg/kg,
and the LD-50 acute human ingestion is thought to be similar - the LD-50
acute human inhalation is considerably lower at an estimated 5-10 mg/kg -
inhaling a gram of dust will almost certainly kill you, as will swallowing a
Those figures are for sodium fluoride, not for hydrofluoric acid, which is
even more toxic. Hydrofluoric acid also gets into the human system by
absorbtion through the skin.
The real problem with hydrofluoric acid is that it is toxic, not that it is
corrosive. Neutralising it doesn't significantly change the toxicity.
Ionic fluoride is equally as toxic as the acid or as the sodium salt - the
main, small, difference is that the salt is slightly less easily absorbed
through the skin.
The percutaneous (through the skin) action is especially nasty as it numbs
the nerves and there is no pain to tell you that you have been exposed -
this also makes systemic poisoning more likely as well.
There is no antidote for gross systemic fluoride poisoning, whether it is in
the form of hydrofluoric acid or sodium fluoride - both work similarly by
depleting the available calcium in the nerves.
Systemic poisoning takes a while to kill, typically 6 to 24 hours, which
makes NaF a better rat poison - the rats can't easily tell each other what
Amputation has occasionally been used in cases where inessential body parts
have been exposed, to prevent death by systemic poisoning. It is the only
known-successful treatment for large-scale acute percutaneous HF insults
(getting too much HF on the skin).
Worse, it only works if you are lucky enough to have only amputatable parts
of the body exposed, a tourniquet is immediately applied after the spillage
and not ever loosened, and you get treatment in a very short time.
Even worse still, there are only a very few doctors in the world expert
enough to be confident and willing to do the amputation - most ordinary
doctors and medics will not even start to consider it before the poisoning
http://www.uwm.edu/Dept/EHSRM/LAB/hfmedbook.pdf will tell you about HF
exposure and it's treatment. However the authors, Honeywell, sell more HF
than anyone else, and they kinda gloss over some of the nastier aspects.
For instance: the deaths seem not to have happened; accidental or especially
chronic occupational exposure apparently does not cause skeletal fluorosis
(anything from "scratchy joints" to crippling hunchback arthritis-like
symptoms); and cutting arms and legs off is called "primary excision" and is
only briefly mentioned (on page 11) with only one reference (49).
Peter and Peter.
Fair enough. I would agree there is no antidote to the effect of HF on human
physiology but Peter N's post spoke of neutralise which is a different
matter altogether. As a chemist for 26 years who has on occaision handled
hydrofluoric acid I am irritated by, and possible over-react to, the
misleading sort of response to dangerous chemicals typical of gutter press
hysteria. Any such chemical can be handled safely given the right knowledge
and suitable precautions, but to demonise it out of hand smacks of tabloid
As far as I remember he rolled it and you couldn't even see a seam, I
think it was multiple layers of the sheet.
I have several bit's that may be from hoses he made, one of them is
average samco, cost a bomb, hose but has the reinforcing visible on the
outside, the second bit actually looks like it was made from tape found
at a slight angle round the former, it is spirally ridged. I know some
he made were all shiny and were indistinguishble from Samco hoses.
So you roll it like a swiss roll around the former, then treat it (pressure
and/or heat) and it bonds the layers?
Interesting. I'm a bit surprised this works, not because I've particular
knowledge of silicon but just I though silicon tended to be pretty inert.
I just had a reply from one of the companies I mailed. They sell it in
50 cm wide rolls either on a polythene backing or on a
fabric[reinforcement]. It sounded like making hoses is what it's
intended for and a range of reinforcment materials are available, the
most popular for intercooler hoses is polyester[the same as coolant
hoses]. Probably find it's seriously expensive;-)
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