Cavity Wax - the Truth, the Whole
Back in 1997 I saw
a test in Practical Classics of a number of anti-corrosion cavity
wax treatments that claimed to be the ‘best test’. Certainly, the test was
quite rigorous, and subjected the treated samples of welded angle iron to
all kinds of horrors including the dreaded salt spray. The waxes were
tested for their ability to penetrate seams, adhere to the bare metal or
rusty surfaces, how much shrinkage they demonstrated during the drying
process and finally their ability to ‘self heal’ over scratches in the
protective layer. The test was carried out over 500 hours (three weeks to
you and me) and the winner was…… Dinitrol 3125, with Plastic Padding and
Waxoyl products coming in a close second. So was this the ‘best test’?
Being in a
half-German household, and having spent nearly ten years on the continent
(we are back there again after 5 years in the UK) I do read the occasional
German classic car mag. Well, as if by co-incidence, one such magazine was
running a similar test at the same time. However, in a predictably
thorough fashion, the German test crew went a few steps further. They
constructed twenty box sections with small openings at each end to
simulate a car sill. These box sections were mounted on stands out in the
open and sprayed internally and externally with salt-water solution on a
regular basis after being treated with the various products. The samples
being subjected all the time to the real conditions of outdoor life: rain,
sunshine, dew and draught.
The initial test I
read was conducted after one year, using an endoscope to peer into the box
sections periodically and photograph the insides. The test results put the
waxes tested by Practical Classics in roughly the same order, but hang on
– why was Dinotrol, Waxoyl and the other waxes so far down the list?
The Germans had
not only tested the common cavity waxes that we are familiar with in the
UK (and which provide advertising income for the UK motoring press), but
also two products that are classed as greases, not waxes and which are not
easily available in the UK. Mineral wax is normally a paraffin and
presumably a grease is somewhat different. Both of these products excelled
in all the tests, but were far and away the only products that would
‘creep’ after application. Also being a grease with no solvent, the layer
does not shrink as there is no evaporation and of course no smell
afterwards (you know the smell of Waxoyl in your car? – that’s the smell
of your wax layer drying, hardening and eventually cracking). The clear
winner was Michael Sander’s Corrosionsschutzfett! (long word meaning rust
Now, I know this
sounds a little beyond belief, but Herr Sander just happens to live in the
next village to where we now to live in Schleswig-Holstein, and after a
tour of his workshops and a look underneath two examples of customers’
cars which he had treated over ten years ago which were up on the ramps.
The cars had both been treated underneath with only paint and his
protective grease – it looked dirty for sure, but completely rust free.
Without hesitation I sprayed 8kg of his grease into my Lancia Montecarlo
in 1997, and another 8kg into my FIAT X1/9 in 2000 – both cars not famous
for their anti-corrosion treatment from new. I can report that on both
Italian cars I have seen ZERO deterioration in the areas that I treated.
One box-section which I unfortunately missed on the Lancia was perforated
within two years!
As for the test in
‘Autobild’, after FOUR YEARS of weather and salt spray, the testers showed
what was left. Only the box section sprayed with Michael Sander could be
removed from its stand without the steel disintegrating into a brown,
crumbling mess. There was simply no competition. What more could you ask?
I am a convert. And so are about 100 body shops in Germany.
So far it’s all
good news, but of course there is a downside. These ‘greases’ are more or
less hard at room temperature (with a consistency similar to lard) and
need to be sprayed into the cavities at a temperature of at least 90° C.
This not only requires special spraying equipment but also some
understanding from the good lady as you heat up litres of ‘orrible grease
on the hob of the newly fitted kitchen! I bought a purpose made spray
pistol, thermometer and a variety of probe nozzles (including a brilliant
360 deg spray for those box sections) for about £100 and some peculiar
apparatus made of cardboard tubes and an old hair-drier to pre-heat the
nozzles and probes. It was fairly messy, and being hot grease you only
have a few minutes per batch before it gets too hard to spray. Although
having done it a few times I have plenty of helpful tips now (like, don’t
do it on a cold day – it won’t work!)
before the hot spraying I scrubbed the wheel arches and floor clean with
warm water and detergent using a variety of brushes or rags and allowed it
to dry thoroughly before treating, taking care to clean up all the drain
holes beforehand. Tip: always cover the entire floor area with decorator’s
plastic sheeting, and tightly cover all brake discs with plastic bags and
tape – I spent a lot of time on my hands and knees cleaning the garage
floor with white spirit the first time!
However, a vital
step before doing this work is to understand HOW the body is constructed
and WHERE are the box sections. I am already planning for the later
spraying of the 96 (once it is welded and painted) and due to the way the
entire SAAB body is put together can only be described as strength itself,
there are very few actual box sections compared to many other cars, but