Tropic Lightning Sherman M-4 Main Battle Tank

Tropic Lightning Sherman M-4
Main Battle Tank
Refurbishment of Sherman M-4
Exterior by Corrosion COPS
August 2009
(808) 676-1963
Sherman M-4 Tank Tropic Lightning
Circa 1990
Front Armor Fastening Points Reflects
Advanced Corrosion
August 1, 2009
Corrosion damage,coating undercutting
and fastener erosion
War Horse History
Screwdriver is used to loosen environmental debris, then
vacuumed prior to needle gun work.
Heavy corrosion caused by years of exposure to tree droppings,
rainfall and metal without corrosion inhibitor protection.
Advanced state of corrosion shows 50% or more loss of material to
fastener heads. This state of advanced corrosion left unchecked
would result in fasteners being consumed by corrosion.
Corrosion abatement will be performed on an ongoing cycle to get
the exterior metal skin of the Sherman back into a better state of
presentation for best static display representation.
Turret view looking down at front hull armor. Note how
environmental debris collects at all crevice areas. Rainfall occurs
almost daily at Schofield Barracks which allows moisture to sit in
crevice areas unchecked to advance rapid decay of metals.
The refurbishment plan is to start at the front armor plate and work to the
rear slope deck at the engine compartment over several years as the budget
for repair permits. Semi annual corrosion control treatments will keep the
armor and steel exterior in the current condition and halt further decay of the
metals.
Several hours of needle gun work is required for
good surface preparation.
Cleaning the surface with rubbing alcohol after needle gunning
insures the surface is free of dirt and oil.
Needle gun work is a slow process of heavy rust scale removal.
Note the layers of rust scale seen in the color of black.
Stages of surface preparation
start
finish
Needle gun work needed to get tight rust removed and to
determine depth of corrosion damage and reveal good metal surface.
before
before
after
after
Progress is slow with hand held needle guns as best surface
preparation for coatings requires complete removal of all rust scale.
Stages of Front fender getting needle nosed
Surface is then grinded to remove loose paint and smooth
surface for paint work.
Finished with rust removal on front plate
before
after
End of day 1: CORTEC Vapor phase Corrosion Inhibitor 391 is
applied as the tank will sit 7 days before more work is performed.
CORTEC VpCI 391 is an environmentally friendly water based temporary
corrosion inhibitor that lasts up to 2 years in high build, is easily removed
when required and provides required protection from any corrosion issues
should delay of future work occur.
We are getting to a clean front armor surface. The painted motif of
jaws and teeth will be removed for complete front plate repaint.
before
after
Rices Tiger has something to smile about with a
cleaned new front plate.
Day 2: Front armor cleaned
and ready for renewed coatings.
Due to budget limitations, the work is limited to correcting the area on the
front armor, the machine gun turret and front fenders with rust streak
removal and corrosion inhibitor treatment. Corrosion inhibitor treatment
includes use of US Army TACOM/AMC approve rust inhibitors as used on
the 25th ID tactical fleet.
Front armor, the machine gun turret and front fenders
prepared and ready for painting.
Front fender
Machine gun turret
Front armor
Prime coating with CORTEC VpCI 396 Moisture Cure Urethane is applied normally wet
film thickness of 3-4 mils which yields 2-3 mils dry film thickness. It is recommended that
under high humidity (60-80% which is Hawaii’s normal humidity range) that the maximum
wet film thickness should be reduced to approximately 2-2.5 mils, and application of two
coats may be necessary.
VpCI-396 is a high solids aromatic moisture cure urethane for use on marginally prepared structural
steel. VpCI-396 is a direct to metal primer for multimetal protection. VpCI-396 should be top coated
with aliphatic urethane top coat for best results. In addition to the outstanding barrier protection,
VpCI-396 also contains Vapor phase Corrosion Inhibitors for additional protection. VpCI-396 is suitable
for immersed structure when applied over CorrVerter® for marginally prepared surfaces; i.e. ballast
tanks or ships. VpCI-396 forms a very hard, but flexible coating that cures in the presence of moisture in
the air. For best results the curing conditions required are a relative humidity between 20% and 80%
with temperatures above 32˚F (0˚C) and below 120˚F (50˚C).
CORTEC VpCI 396 Moisture Cure Urethane
FEATURES • Low VOC • Single component package • Can be coated at a relative humidity up to 80%
• Can be applied at low temperatures • Excellent adhesion • High solids
METALS PROTECTED • Aluminum • Cast iron • Galvanized steel • Steel
TYPICAL APPLICATIONS • Bridges • OEM • Structural steel • Storage tanks • Ballast tanks or ships
TYPICAL PROPERTIES •Appearance Viscous aluminum liquid, dry to recoat time Minimum 4 hr. @
77°F (25°C), 55% relative humidity. Maximum time to Recoat 2 weeks after initial application (solvent
wipe may be required). Dry to touch time 1 hr. @ 77˚F (25˚C), 55% relative humidity. Fully Cured 7
days @ 77˚F (25˚C), 55% RH Film type Hard. Flash point 78˚F (25˚C) Non-volatile content 67-72% by
weight (60-62% by volume). Shelf life 1 year. Theoretical spread rate 978 ft2/gal @ 1-mil DFT (24
m2/l @ 25 micron DFT. Viscosity 500-1100 cps at 6 rpm VOC 2.8 lb/gal (0.33 kg/l). Density 9.2-9.7
lb/gal (1.10-1.16 kg/l). Coefficient of Friction 0.20. Adhesion 5B. Film Hardness 4H-7H Temperature
Resistance -150˚F to 300˚F (Fully Cured) (-78˚C to 150˚C).
All CORTEC products contain the corrosion inhibitors amine carboxylate. The organic
chemical rests on the metal surface as a crystal.The inhibitors are attracted to the metal
surface as the crystal is charged + (anodic) and - (cathodic). Since metal also contains anode
and cathode due to the manufacture process of blending similar but slightly different metals
in the foundry process, finished metals then start to rust almost immediately after
production as the metal moves from liquid to solid material.
When oxygen and moisture come into contact with the crystal, the amine carboxylate crystal converts to
a film and then the inhibitor migrates or travels 90 nanometers into the metal substrate. Chlorides travel
to 80 nanometers thus there is a 10 nanometer protection zone (width of 2 human hairs ) that the
chlorides cannot over come because the amine carboxylate is a dipole rust inhibitor which protects both
+ and - poles. Many coatings purport to have corrosion control properties. Those that do say their
coatings have corrosion inhibiting properties lack explanation on how they work to protect metals.
Typically these competing coatings are without any inhibitors in the finished chemical, thus many do not
last long and wear out soon after application.
Always ask your representative about this fact before deciding on your choice of coatings. For more info
on CORTEC: www.cortecvci.com
CORTEC VpCI 396 was allowed to cure over a week prior to
OD green application.
Standard water based acrylic finish coating is applied in computer
matched color. CORTEC VpCI 396 can be over coated with many
coatings. Best results come with CORTEC VpCI 384 urethane coating.
Once the OD green has properly cured, new jaws and teeth
will be painted on the front hull.
Tropic Lightning Museum has commissioned quarterly PM service for removal of
environmental debris from trees as acting curator removes droppings to wet OD green
coating. Quarterly service provides a proactive system to corrosion which over time saves
the static display and has proven to have a ROI of 6.5 to 1. Savings of future labor dollars
occurs and allows use of the budget for other projects.
Rust Stain Removal
Use of ENVIROKLEAN Rust Stain Remover allows surfaces to be
cleaned of rust oxides without damage to original coatings.
Rust Stain removal using Enviroklean
EnviroKlean
Stain Neutralizer and Multi-Purpose Cleaner
Brush roll or spray EnviroKlean on surfaces where clean up is required. For best procedure do not allow
surfaces to dry. For quicker removal of unwanted stains use of Scotchbrite abrasives will provide fast results
and use of less product will occur. If surfaces should dry, reactivate by application of more product to
previous treated but dried area. Once surfaces are cleaned, rinse with fresh water and the job is complete.
All debris is removed from areas that are not included in the first stage of
complete refurbishment. Surfaces are blown off with compressed air
and rinsed with potable water.
Rust inhibitor CP-90 is sprayed to the tank.
End of first stage of refurbishment
before
after
CORROSION COPS
When you have Rust – Think of Us and call
(808) 676-1963
www.corrosioncops.com
For best results for any corrosion control program
Proper selection of products
Required preparation
Application of product
Follow up inspections with documentation