1) The document discusses testing of aluminum ceramic coatings used in the automotive, aerospace, and oil/gas industries to provide corrosion protection at high temperatures. 2) It describes the materials, application process, testing, and potential issues with improper application of the coatings. Key application steps include surface preparation, multiple coat application, and heat curing. 3) A case study examines coating samples where either the ceramic or sealer layer was under cured, finding that under curing the ceramic layer can cause premature failure in testing or in the field. Proper quality control steps during application are important.

1. Case Study: Aluminum Ceramic Coatings Proper
Application and Testing
Introduction
The coating I am discussing today was brought about in the
automotive and aerospace industry, as protection from high
heat on car fires and turbine blades for jet engines. It was
brought to the oil and gas industry, by engineers that had a
use for it as an anode on fasteners and performed well on
ASTM B-117, giving 5,000 salt spray hours to carbon steel.
The only draw back was that the nuts needed to be over
sized by 10/10000 in allowance to the 1.8 mil total coating
thickness.
Getting the coating tested and specified from the automotive
industry to subsea industry was no easy task and there were
many standard test organizations that did not comply to one
another and new testing was needed. The rules for
application were poorly addressed, or I should say left open
for interpretation by the applicator.
Methods / Materials
Aluminum Ceramic Coatings (or ACC as we will call it
through out the paper), have been in oil and gas use since
1999. As a sacrificial coating for subsea systems.
ACC is a high performance coating that can be applied to
metallic and non-metallic surfaces to provide resistance to

2. corrosion, thermal oxidation, abrasion and erosion. ACC is a
water based slurry comprised of an acidic
chromate/phosphate binder system containing dispersed
aluminum particles. The material is applied by spraying with
conventional. After being heat cured, ACC produces a
ceramic/ metallic composite coating that can be effective in
thickness as low as .75 of a mil.(0.00075 inches.)
ACC provides protection to metal surfaces against
atmospheric and chemical corrosion, wear, erosion, thermal
oxidation, pitting and other destructive forces. The coating
can withstand salt spray exposure for thousands of hours
and protect parts at temperatures up to1200°F. By protecting
the surface from corrosion and oxidation, ACC can improve
the fatigue strength characteristics. It can be made
conductive and sacrificial to all steels and many other alloys.
It will extend the life of critical parts and, therefore, cut costs
through savings in parts replacement, repairs and lost
production time. Often, lighter gauge or less expensive base
metals can be used to take advantage of the unique
protective properties of ACC.
ACC is used on all types of metal parts and surfaces. In the
oil and gas industry, it can give protection to riser bolts,
running tools, subsea BOPs, works well with respect to
Thermal Spray Aluminum parts, valves. High heat
applications include boilers, heat exchangers, furnaces. In
the chemical process industry ACC provides protection from
corrosion and oxidation of steam valves, pipes and other
high-temperature applications.
Technical Data
Color. (When mixed). Gray-green
Total solids by weight. 47- 56%

3. Weight per gallon 12 - 13.3 lbs.
Specific gravity 1.44 - 1.6
The coating cures 30 minutes after the entire part has
reached 650°F. It must reach the 650°F for two reasons; one
is that the ceramic will return to slurry (mud) if not fully cured
and two is that a chemical change occurs in the hexavalent
chrome molecular structure and transforms into trivalent
chrome at that temperature.
The coating can act as an anode, because the ceramic holds
aluminum flake particles in suspension against the surface of
the metal substrate. Forming an electrochemical bond in an
electrolyte such as salt water and allowing the aluminum to
sacrifice it's self in place of the metal substrate and forms
aluminum oxide and acts as a seal.
The aluminum oxide then becomes an even better barrier
layer and anode. This occurs at a coating thickness of at
least (>.75 mils), no less. Even when working with fasteners
you must have this thickness of the ceramic , in order to
have the system work.
The issues we see with the coating system is in its

4. documentation of application, quality control and
specification as something other than it was intended.
Improper Applications and Quality Checks
1. Abstract
The discussion of improper application and quality
checkpoints of a ceramic coating has come up with
applicators applying by academic direction only and very
little hands on experience. A manufacture can only direct an
application so much and an OEM can only write obvious
quality check points. Even with a safe specific analysis of the
application it is still left up to experience and interpretation of
the product.
2. Instructions
The instructions for application of the ACC listed as they are
can be preserved different ways.
Application instructions for Aluminum Ceramic Coatings
Surface preparation
Deposits of oils and organic material must be removed by
thermal degreasing or alkaline cleaning prior to abrasion
procedures. Parts should only be handled while wearing
gloves subsequent to degreasing. Grit blast parts using new
60 -100 mesh alumina at 80 psi air pressure.
Application of coating
(ACC) is supplied ready for use at application viscosity and
does not require thinning. Some name brands will give
special instruction as to what viscosity Adjustment Solution
to use if any. Condition the five gallon pail of coating on a
five-gallon paint spinner to disperse any settled solids.

5. Transfer the coating to a separate container by screening
through a 100-mesh screen or medium mesh paint filter
cone. Screen the entire contents of the original container to
assure that no solids remain on the bottom. Be sure to
inspect the container after emptying.
For manual spray operations, transfer the coating to the
spray gun cup and lightly shake the spray gun regularly
during use to keep the solids suspended and to assure a
homogeneous mixture. Suitable spray gun equipment is the
DeVibiss EGA 502 (F tip/395 air cap), EGA 530HV series (F
tip and 395HV air cap) or TGA-515 ( F tip and CV 39-90 air
cap). The Blinks 115 or 26 spray guns with 76SS needle and
76 x D76S fluid and air cap are also suitable.
Other spray guns may be used provided fluid tip and needle
orifice are sized at 0.040- 0.045 inches.
When fully automatic or semi-automatic spray equipment will
be used, a separate coating reservoir equipped with a
centrifugal pump and auxiliary prop stir agitator must be
used. Additionally, the automatic spray guns must be fitted
with a flow through closed loop fluid body ( I.e., Paasche A-
JU type gun).
For optimal coating performance, the surfaces to be
sprayed, dried and cured twice; however, many applications
may be specified where one coat deposition will be
sufficient. Typically, dry film thickness of 1.0 - 1.5 mils will be
satisfactory for most applications. Drying and curing are
explained in the following section.
Adjust the atomizing air pressure to 30-40 psi for manual
conventional air atomized spray guns and 50-75 psi for
manual HVLP spray guns. For automatic spray guns, follow
the manufactures suggested air pressure recommendations

6. for the style gun being used. Set the fluid adjustment nozzle
to deliver a strong fine mist. Hold or position the spray gun
approximately eight (8) inches away from and directly
perpendicular to the surface to be coated. Apply a wet even
coating to the surface by gradually building up the coating in
an overlay pattern using multiple passes as required. Porous
surfaces such as powdered metal and cast iron tend to
absorb coating and will require more passes to develop the
proper film build. The wet coating should be green colored
when applied, but should not create build ups or drips and
runs or fail to dry or flash to gray. Increasing spraying
distance, lessening air pressure or fluid flow or changing to a
finer spray nozzle will prevent excess buildup of coating. The
coating must not be applied to the part in such a way that the
coating dries to gray immediately. Should this condition
occur, then reducing the spray gun to part distance, or
reducing the atomization air pressure, or increasing the fluid
delivery rate or a combination of above should correct the
problem. ACC can be washed off with warm water, dried and
recoated prior to curing if required. This is possible both
before and after oven drying. Cleanup is simple using warm
water.
Note: Cleanup water will contain hexavalent chromium
compounds and must be captured and disposed of properly
as chromate containing hazardous waste. Do Not dispose of
chromate containing cleanup water in municipal or sanitary
sewage systems. Refer to MSDS for additional waste
treatment information.
Drying and curing procedure
After allowing ACC to air dry for about ten minutes, during
which time it changes from green to light grey, the parts are
then ready to be dried at 150- 175°F for a minimum of 15
minutes. The air-dry procedure can be modified to

7. accommodate continuos process applications. ACC is cured
in a 650°F -0°/ +25°F oven to achieve a minimum part dwell
time of 30 minutes at 650°F. If feasible, parts may be self-
cured by placing them right into their intended high heat
application and allowing the process heat to do the curing.
ACC cannot be over cured, and under cured coatings are
detectable after burnishment by placing a wet cloth on the
coated surface and observing if any binder leaches onto the
fabric as exhibited by yellow color.
Electrical conductivity must be established to obtain
maximum salt spray performance. Mechanical burnishing
subsequent to curing will accomplish this. Recommended
methods are: glass bead or grit burnishing @ 20-30 psi
(suction type blasters). Another method by which ACC is
made electrically conductive is to post cure at 1050°F (part
temperature) for at least 30 minutes. Conductivity may be
tested by placing resistance meter probes one inch apart.
The reading should measure below 5 ohms.
(Sealers and other top coats Many top coats are used to either seal the porous
ceramic, or to allow for in service use. Fluropolymers, fusion bonded epoxies and
even rubber has been used over the surface of the ceramic.)

8. 3. Methodology
Case Study Investigation: The reason I broke the test up into
four segments is to show what is possible when using a two
coat system. In the study, I under cured the ceramic coating
on plates 3 and 4 and under cured the top sealer coating on
plates 2 and 3. In doing so I am able to make mistakes and
problem solve issues that may have come about in
production, but have yet to be covered.
4. Findings
What were the results of your investigation and what
answers do they give you?
There is not always a consistency to every test and multiple
tests are required. Certifications of Coating and quality check
points would not only need to be signed off on but thermal
coupling records, burnishment mil readings before and after
water test and multiple ohm readings would all go a long way
to securing a well processed application. ( Many written
procedures are not direct enough as to when in process
quality checks should be made. For instance the DW test
should only be done after the burnishment of the ACC.)
DW Test- The deionized water test has been standard
ceramic cure test for the past almost twenty years. The only
issue with it is that it may take 24 hours for the hexavalent
chrome if not cured, to show up on the outside of a non-
burnish part. Usually a green or yellow tint on a wet rag, or
tint in a pool of water left on the ceramic. Indicates that the
part is not yet fully cured. Surface ceramic can cure on the
surface practically, that is why it is important to water test the
ceramic after burnishment.
The deionized water test which is standard with checking the

9. hexavalent chrome binder has transferred into trivalent
chrome and cure of the ceramic, came out negative for
hexavalent and positive for cure on all samples. The test
was performed for 20 minutes and the substrate had cooled
to room temperature before performing the test.( this was
prior to the burnishment of the ceramic.) When the deionized
water test was performed after burnishment the test
responded quit well to the uncured ceramic hexavalent
chrome still present.
Case Study: When applying the de-ionized water test, all the
samples past while the plates were at room temperature.
Even though two of the four were under cured.
5. Conclusions
What were the results of your investigation and what
answers do they give you?
The conclusion was that the water test needed to be
performed after the burnishment was completed in order to
reveal the presents of uncured hexavalent in the ceramic.
Too many variables are recorded on the outside of an
unburnished ceramic. That is another reason to incorporate
a thermal coupling device in order to read part temperature,
rather than oven temperature.
Analysis
Sample 1. Ceramic Cure/ SealerCure. Bases to work from
and match the other samples. Many people have questions
on the look and feel of the product. Burnishment of the ACC
will give off a shine when properly burnished
Sample 2. Ceramic Cure/ Sealer Uncured. Easily checked
with MEK rub test and find at fault. If top coat fails rub test,

10. then deconstructive test to check ceramic level should be
made.
Sample 3. Ceramic Uncured/ Sealer Cured. Findings
depend on certification of in processes testing of coating
records by applicator. Certification in processes records
should include;
1. athermalcouplingtemperatureofthepartsreaching650°Ff
oranhourperinchof part thickness
2. a mil thickness reading after burnishment
3. adeionizedwatertestoftheceramiccoatingafterburnishme
nt.*
4. Anothermilthicknessmeasurementafterthedeionizedwat
ertest,tocheckforloss of coating during the water
test. If there were no records, or falsified records of the
thermal coupling and the in process testing, you would
have to then rely on destructive lab tests.
a) Hach CH-8 Hexavalent chromium test
b) Deionized Water test with removal of the sealer by
burnishment, not burn-off.
c) ChromaVer3powderpillowsfromHachcompanyandWhat
man#40filterpaper.
(Provide the three lab tests. Reference 3-6)

11. This is by far the most damaging occurrence and
unfortunately the most common. If the ceramic is under
cured at 450°F and allowed to pass, it will fail within days. If
the ceramic is under cured at 550°F it will fail in a matter of
months. If the ceramic coating is under cured at 650°F with
out the part curing long enough. (Usually occurring due to part
metal thickness not being taken into consideration.) The part will
fail in the field and return
back to its slurry application no matter what sealer is
present. Coming in far short of its intended 5000 salt spray
hours. Also being deployed into the field and failing while in
service.
Sample 4. Ceramic Uncured/Sealer Uncured. Easily
checked with MEK rub test and find at fault. A deconstructive
water test and applicator's certification of coatings would
determine the ceramic layer to be under cured as well. If the
top coating is found to be under cured, a deconstructive
water test should follow. Deconstructive testing would
require the removal of the sealer and one of the three test
listed above in sample 3, References 3, 4 and 5.

12. Final Note.
The results from the test Sample 3 again is the real reason
for this study and is a concern for all the reasons stated. The
coating does a good job and lives up to its title, but not all
applications are equal, or should be treated so. The action
taken was that several of the in process tests were made
mandatory and thermal coupling was specified for both two
coat systems. I would go one step further and ask for a
submission of parts be coated and tested to ASTM B-117 for
a total of 3,500-5,000 salt spray hours and a cut test made to
check adhesion.
References:
1.ASTM B-117 salt spray test.
2.ASTM F1428 Standard Specification for Aluminum Particle-filled Base
coat/ Organic or Inorganic topcoat, Corrosion Protective Coatings for
Fasteners.
3.SLP 62-2 Cure Evaluation 4.SLP 62-4 Cure Evaluation 5.SLP 42-1
Coating Cure Evaluation
Thanks goes to Bruce McMordie with Coatings for Industry, Bill Fabiny with
Dow Chemical, Lonnie Fuqua with NOV, Anand Samant with Praxair, Brian
Harpold with Numerical Precision, Bolt Science and Array Coating
Technology.