Jaguar Frame Resotration
Corrosion Protection of Frames
Scott Selbach - Feb 1999
Due to my expertise in the field of the
corrosion protection of steel substrates, several people on the list suggested I
write this thesis on the preservation of Jaguar frames. This is a very
cursory dissertation, but should provide the basics anyway. If this topic
interests you, read on.
The coating of any steel surface for corrosion
protection can be divided into three important areas: 1) surface
preparation, 2) coating selection, and 3) coating application. The
weak link theory applies here and each of these aspects has to be done
There are a number of ways to prepare a steel substrate,
depending on the intended use, desired result, and budget. The basic
methods of preparation are: 1) solvent cleaning (includes washing), 2)
abrasive blasting, 3) hand/power tool cleaning, and 4) chemical cleaning.
All surfaces to be prepared must be washed and solvent cleaned. We can fly
to the moon but cannot successfully paint over grease, oil and salts.
Washing with a solution of hot water and a strong detergent such as TSP
(tri-sodium phosphate), Dirtex, Soilax, etc. will remove road salts and general
dirt. The solvent cleaning with MEK (methyl ethyl ketone), toluol, xylol,
or wax and grease remover will remove grease and oil deposits. Most
preparation methods do not remove this and actually force it into the steel
surface. Remove the contaminants first, then de-rust the steel.
The best prep for maximum
long-term corrosion protection is abrasive blasting. This removes existing
corrosion and prepares the surface to accept a corrosion resistive
coating system. The abrasive can be any one of a number of media including
silica sand, coal slag (Black Beauty), plastic, steel, water, ice, aluminum
oxide, glass, sodium bicarbonate, sponge (believe it), corn cobs, walnut shells,
etc, etc. Silica sand and Black Beauty are the most widely used as their
characteristics best suit our needs. The results of an abrasive blast are
measured by the cleanliness and profile. Cleanliness refers to how much of
the corrosion in the steel is removed and is important to the longevity of the
corrosion protection. Profile is the texture of the blasted surface and is
important to the adhesion of the primer.
Hand and or power tool
cleaning is simply using a wire brush or other such device by hand or
powered. It will not get the surface as rust free and provides little or
no profile. The roughness left after using a grinder is not an acceptable
profile. You may have cleaned a steel surface with a powered wire brush in
the past and thought that it was rust free, but if you were to compare that to a
"white metal" blast, you would see a huge difference. A lot of
corrosion is left in the steel pores which will come back to visit you
later. The attractiveness of hand/power tool cleaning is that it is
inexpensive, can be done in the home setting with little tool investment and
expertise, but it does compromise corrosion protection and longevity.
Chemical dipping can also be done but I think is better left to the body
panels. Frames have a lot of inaccessible areas that are difficult to
purgue the chemicals out of and that can cause problems later.
of this said, let's get to a frame. The outside of the frame is best
prepared by abrasive blasting to a silvery steel look with a profile that feels
like medium sandpaper. Don't do this inside your garage or you'll get
spent abrasive everywhere, and I mean everywhere. The abrasive can be
gotten out of the inside of the frame by rotating and tipping it combined with
compressed air blowing it out. That abrasive that is left in the frame can
stay there, not enough to worry about and non damaging anyway. This is not a
clean process, but if done with a little precaution, it doesn't have to be
terrible. Properly suit up in a Tyvek suit, taped at the wrists, ankles
and neck and wear a good hood and gloves. Always try to paint a surface
soon after preparation to prevent rust-back which can happen very quickly,
especially in humid environments. The rule of thumb in industrial
applications is to apply primer within 24 hours of blasting.
The inside of a
frame is a different situation. Inaccessibility prohibits blasting and
hand/power tool cleaning. Truthfully, there aren't many good
options. Chemical dipping is about the only thing that will get to all the
inaccessible areas inside the frame but this comes at a price. Dippers
neutralize the aggressive de-rusting acids, but as mentioned before not all the
solution can be gotten out leaving them in the frame and they tend to keep
eating away at the surfaces. I wouldn't dip anything that I wasn't
absolutely sure I could purge 100%. You also can't use conventional paints
inside the frame. They won't adhere to the poorly cleaned surfaces and you
can't get them in every nook and cranny without pouring them in. If you do
that, though, then the coatings will build up somewhere, get too thick, crack,
fall off and then you have no corrosion protection. For my money,
unless the frame is really badly rusted, I would get as much of the crap out of
the inside of the frame as possible by water and air power and poking around and
apply a good thick coat of Waxoyl. This stuff will wet into the dirty,
rusty surfaces, passivate the steel, and you can apply as much as you need to
get it to flow all around the inside the frame without worrying about how thick
it gets. Low tech, but awfully effective.
Most of the work is done; surface prep is the tough part. There are
many different generic classes of coatings. For corrosion protection, you
can't beat zinc primers (they will even outlast a galvanized surface), but
epoxies offer the best combination of protection and ease of application.
Over a blasted surface, apply two coats of a good epoxy primer.
McMaster-Carr or Grainger will have a Rust-Oleum product, or your local auto
paint store will have products like PPG's DP40 or DuPont's Corlar primers.
They are all two component products meaning there is an "A" and a
"B" that have to be mixed thoroughly together. Once mixed there
is a finite potlife that you have to use it within or it goes bad. Once on
the surface, there is also a finite recoat window that you have to apply the
topcoat within. Read the label directions entirely and follow them to the
letter. After the epoxy primer(s), apply one coat of a urethane finish
coat (like DuPont Imron) and the frame will look great. Imron is a high
gloss but other products are available in lower sheens, if desired.
Urethanes are also two component, so again, read the directions.
Over a hand/power tool cleaned surface, there are coatings the will
offer decent protection over little or no profile and with some existing
corrosion in the steel. POR15 and Miracle Paint are coatings for this
condition, as are surface tolerant epoxy mastics. STEM's will outperform
POR15 or Miracle Paint and in an aggressive chemical exposures this difference
would be big, but in this mild exposure, the difference in performance may not
be a big deal. STEM's can be effectively applied directly over tight rust (no
loose or flaky rust) with applications known to last 12-15 years without
evidence of re-rusting. POR15 or Miracle Paint will probably last 7-10
years, maybe more, maybe less, hard to predict (various factors such as - rural
Utah is a lot different exposure than coastal Florida, miles driven,
Some people mention galvanizing and powder coating of frames.
Both are coating options, albeit expensive ones. Galvanizing is basically
permanent (on a car frame, anyway) and can be painted over. The frequent
failure of painting galvanized surfaces is due to lack of knowledge, not any
resistance of galvanizing to be painted. Powder coating is a process left
to an expert with an elaborate facility set-up and is available in about any
color and sheen. Touch up of the inevitable ding is more difficult but
then powder coatings are more ding resistant. Only you can decide if you
want to go to the extent and cost of either of these processes. Both are
excellent, but this discussion has been aimed more at the do-it-yourselfer.
With surface prep being 65% of the job, coating selection being 25% of the
job, there isn't much leftover for application. This is the fun part
though, that transforms the frame into a well protected and beautiful
piece. About all I can say about application is to read the label
directions of the coating you chose. These products were designed with
specific application parameters. Many of these coatings were designed for spray
application, and if you've gone this far, you'll be a lot happier with the
sprayed finish. A sprayed finish can mean the difference between looking
like a professional versus an amateur result. Trust the coating's designer
and follow his instructions, more is not always better. Avoid that
temptation by putting the coatings on at the recommended thicknesses.
Coating thickness is measured in mils (1 mil= .001") and if you exceed the
designed millage by too much then drying, running, and cracking can become a
problem. Too little and you haven't got the protection you may need.
Oh, by the way, I mentioned
before about putting Waxoyl inside the frame. Paint absolutely doesn't stick to
wax, so finish painting the outside of the frame first, then apply the Waxoyl inside, then clean your sloppiness
from the painted outside surfaces with mineral spirits.
this covers the subject and has helped in some way. If all steel coating
projects were this easy, however, I wouldn't get paid enough to keep my car
collection in Castrol, so there are many variables that can affect the selection
of prep method, coating, etc. Private email me at email@example.com if you have any further
questions. I would be glad to recommend a coating process customized to
your conditions of capability, intent and budget.
'60 Morris Minor 1000
'54 Ford F100