NALTIC Industrials, LLC


Ready to use, RoHS, WEEE, ELV, REACH, and OSHA PEL compliant Trivalent Chromium Conversion Coating Used for Immersion, Brush and Spray Applications which also provides a distinct color for easy processed part identificatio


CHEMEON eTCP RTU is a ready to use chemical conversion coating for aluminum, magnesium, zinc, and their alloys. The resultant conversion coating has a noticeable blue to purple color which provides visual verification that the coating has been applied. It produces a protective coating, which minimizes corrosion as well as improves adhesion capabilities of the surface. Applications include:
Hexavalent chromiumfree conversion coating on aluminum, magnesium, and zinc

Noticeable color change

Unpainted corrosion protection on aluminum that is comparable to hexavalent chromium

Meets contact electrical resistance requirements of MILDTL81706

Pretreatment for paint and powder coat applications, which results in extended corrosion resistance

Field touchup for chromate and anodic coatings

Seal for anodic coatings on aluminum, including Type II B thin film and Type II colorless, dyed, and electrolyticallycolored coatings

Recoat stripped substrates such as aircraft

CHEMEON eTCP RTU meets the following specifications: MILDTL81706 (Qualifying Specification for MILDTL 5541), Type II (nonhexavalent chromium), Class 1A and Class 3, Methods A (spray), B (brush) and C (immersion) as well as MILDTL5541, Type II, Form III, Class 1A and Class 3, Methods A, B and C.
CHEMEON eTCP RTU has the following U.S. Patent: 10,533,254.


Chemical Composition ………..Trivalent Chromium, Activators
Appearance……………..Dark Violet

Odor ..…………...None to mild

Bulk Density …………………8.5 pounds/gallon at 68 °F (20 °C)

Freeze/Thaw Stable………..……….Yes

pH……………………………2.5 3.5


General Operating Conditions for Use as a Chemical Conversion Coating:

Application…………………..Immersion or spray
Concentration………………………80 – 100% by volume, depending on application
Water Quality …………………….Deionized (DI) or reverse osmosis (RO) is preferred
Temperature………………………..68 °F – 80 °F
Time ………………………1 – 15 minutes (5-6 minute recommended)
pH…………………………3.6 – 4.0 (3.8 to 3.9 recommended)
pH Decrease ………………….Gardacid SO4 or sulfuric acid diluted to 5 – 10%
pH Increase…………………..Gardobond-Additive H 7212 or caustic soda 5 – 10%

General Operating Conditions for Use as a Seal for Anodic Coatings on Aluminum:

Concentration…………………..80 – 100% by volume, depending on application
Water Quality …………………Deionized (DI) or reverse osmosis (RO) is preferred
Temperature……………………68 °F – 80 °F
Time …………………………1 – 10 minutes (2-5 minute recommended)
pH……………………………..3.5 – 4.0 (3.8 to 3.9 recommended)
pH Decrease ………………Gardacid SO4 or sulfuric acid diluted to 5 – 10%
pH Increase………………Gardobond-Additive H 7212 or caustic soda 5 – 10%

Notes for Use as a Conversion Coating on Aluminum:

To achieve optimum results, the aluminum substrate must be cleaned and activated prior to treatment withCHEMEON eTCP RTU.
Excellent results have been obtained using a mild alkaline cleaner at the lower end of its operating temperature range. Typically, etching cleaners do not perform as well in applications where good unpainted corrosion resistance is needed. One suggested immersion cleaner is Gardoclean T 5847, formerly
Aluminum Cleaner NST.

Non-silicated cleaners are preferred.

After cleaning and rinsing, surface activation should be performed using a strong acid such as 50% nitric acid. A less concentrated acid product with additives such as Gardacid P 4299, formerly Deoxidizer LNC, may also be used.

The pH of a CHEMEON eTCP RTU bath should be carefully monitored. At no time should the pH of the bath be allowed to rise above 4.0. All pH adjustments should be made slowly and with strong agitation to ensure complete and rapid mixing. Good agitation is required when increasing pH in order to minimize localized precipitation.
During immersion applications, the CHEMEON eTCP RTU bath should not be agitated.

After coating in CHEMEON eTCP RTU, parts should be thoroughly rinsed. DI or RO water is preferred.

Peak metal temperature for dry off should not exceed 250 °F.

Typical coating weights range from 20 to 45 mg/sq ft.

Age coated but unpainted panels 24 hours prior to exposing to Neutral Salt Spray testing.

For applications on previously-coated and stripped substrates or touch-up field repairs, contact the CHEMEON Technical Center at 1-888-782-8324 or

Notes for Use as a Field Touch-Up on Aluminum:

Thoroughly clean with an abrasive pad such as 3M Scotch-Brite, rinse, apply CHEMEON eTCP RTU at 25% by volume, pH 3.6 – 4.0 at ambient temperature for 10 minutes and 100% v/v.

Notes for Use as a Conversion Coating on Magnesium and Zinc:

For specific applications and process parameters contact the CHEMEON Technical Center at 1-888-638- 2527 or

Notes for Use as Seal for Anodic Coatings on Aluminum:

The anodized aluminum must be rinsed well before immersion in the CHEMEON eTCP RTU seal. After treatment, only 10 – 30 seconds in clean, room temperature water is suggested for a post-seal rinse.

For use with dyed surfaces, excluding those that have been electrolytically modified, use a low concentration of CHEMEON eTCP RTU with a long immersion time to obtain maximum color retention.

For electrolytically-colored coatings, the best results are achieved by using a high concentration of CHEMEON eTCP RTU with a mid-range immersion time.

Performance on Anodized Aluminum

For all concentrations and immersion times outlined in the General Operating Conditions section of this Technical Information sheet, CHEMEON eTCP RTU will provide neutral salt spray resistance in accordance with ASTM B 117 to 3,000 hours or more on the anodized, CHEMEON eTCP RTU sealed surface.

For application of organic coatings on top of the anodized surface, the CHEMEON eTCP RTU sealed
surface provides an excellent base for adhesion purposes.

Bath Make-Up:

Adjust pH as needed while pouring in Chemeon eTCP RTU.

Bath Maintenance:

• The pH of the bath should be checked regularly. It is important that the pH of the bath does not exceed 4.0.
• Use of a fluoride resistant pH probe is recommended. To clean staining off the probe, dilute nitric acid or a commercially available ink cleaning solution are recommended. Light scrubbing with a Kimwipe might be required to remove stains.
• Measurement of the bath concentration may be performed by using spectrophotometry.

The CHEMEON TCP-HF technical service group provides free monthly evaluation of concentration and pH. Please contact the CHEMEON Technical Center at 1-888-638-2527 or if you are interested in this service.



• Spectrophotometer capable of measuring absorbance around 565 nm
• Quartz or plastic cuvettes
• Plastic pipettes
• Adjustable volume precision pipettor or equivalent volumetric pipettes (Class B glassware is acceptable though Class A is more accurate)
• 100 mL volumetric flasks
• Plastic storage bottle for primary standard and 10% v/v sulfuric acid to rinse bottle prior to storage

Prepare the primary standard

Remove at least 1L of solution from the well-mixed drum or bucket of eTCP RTU. Analyze the mixture using the titration method described below. It is recommended that triplicate analyses are performed to ensureaccuracy.

Required Materials:

• Stirring hotplate
• 100 mL pipet
• Plastic Pipet
• 50 mL burette
• 50 mL graduated cylinder
• Filter funnel
• Fine porosity filter paper (8 μm pore size recommended)
• 250 mL Erlenmeyer flask
• 10% w/w sodium hydroxide
• 35% hydrogen peroxide
• 17% v/v hydrochloric acid
• Potassium iodide
• Starch indicator solution

Titration Method:

1. Pipette 50 mL CHEMEON eTCP RTU into a 250 mL Erlenmeyer flask
2. Bring to 100 mL total volume with DI water
3. Add approximately 40 mL sodium hydroxide solution
4. Add approximately 5 mL hydrogen peroxide, stirring for 5 minutes
5. Add another 5 mL hydrogen peroxide, stirring for an additional 5 minutes
6. Boil the solution for 40 to 50 minutes to decompose excess hydrogen peroxide
a. The solution will be highly effervescent at first
b. Be careful to avoid boiling the solution over
c. Do not allow the solution to evaporate below 50 mL, add DI water back as necessary
7. Allow the solution to cool. The solution will be bright yellow and cloudy with precipitate
8. Filter the solution through a fine-grained (8 μm) filter paper
a. Rinse the filter paper and precipitate using a wash bottle filled with deionized water until the
precipitate is colorless
b. Retain the filtered solution (“filtrate”)
c. Important: the solution must not be cloudy
d. If the solution is cloudy it must be filtered again with a finer grade filter paper

9. Add DI water as necessary to bring the solution volume to approximately 100 mL
10. Prepare the titration apparatus. The burette should be prepared with 0.1N sodium thiosulfate
11. Add 80 mL hydrochloric acid to the filtrate. The filtrate will turn from yellow to orange
12. Add 2 g potassium iodide. The filtrate will turn red. Mix until completely dissolved
13. Immediately titrate the solution with 0.1N sodium thiosulfate until the solution is pale red-yellow
14. Add 2 mL of starch solution and titrate to endpoint (clear blue/gray)
15. The endpoint must persist for approximately 30 seconds. If the endpoint is not stable for 30 seconds, add additional sodium thiosulfate dropwise until the endpoint persists.

Concentration Calculation:

CHEMEON eTCP RTU (% by vol.) = (volume in mL of 0.1N sodium thiosulfate used) x 3.12

This is now the known primary standard (100% v/v). Store it in an airtight plastic bottle which has been rinsed with a small amount of dilute sulfuric acid before rinsing with the standard. Label it appropriately (concentration, date, substance). Test the solution by titration every month or so (depending upon the
customer’s method of storage) to make sure the concentration has not drifted. If the concentration drifts over time, simply re-analyze by titration and remake the calibration curve.

Once the concentration is accurately known, use the solution to make UV-Vis secondary standards by dilution.

Procedure for making 75%, 50%, and 25% secondary standards by dilution:

Three additional standards must be prepared. The solution as received will be the 100% standard which can be diluted down to make 75%, 50%, and 25% by volume secondary standards.

Rather than try for an exact concentration, use dilutions that are simple to perform. For example, if the RTU is at 106%, make the next secondary standard at 53% using a simple 1:1 dilution rather than trying to dilute down to an exactly 50% standard.

Best Practices are to make the secondary standards on the day of each analysis. They may be saved and
reused, although this practice is discouraged. The Primary standard may be saved and re-used. The
concentration of the primary standard should be checked periodically (by titration) to ensure the calibration is
still valid.

Procedure for analyzing CHEMEON eTCP RTU bath sample:

1. Turn on the spectrophotometer. Allow the instrument to warm up according to manufacturer’s specifications.
2. Dilute the standards and bath sample down 1:100 (500 μL into 50 mL total volume with DI water).
3. Set the wavelength of the spectrophotometer to 565 nm. This wavelength should be determined ahead of time with the standard 100% eTCP RTU.
4. Fill the cuvette with deionized water and wipe down the outside walls of the cuvette so they are free of fingerprints, streaks, and moisture.
5. Place the cuvette in the spectrophotometer and “zero” the instrument according to manufacturer’s specifications.
6. Measure the absorbance value of the deionized water according to the manufacturer’s specifications.
Record this value. It should be very close to zero.
7. Using a clean plastic pipette, refill the cuvette with one of the previously prepared CHEMEON eTCP RTU
standards, clean the walls of the cuvette again then place it in the spectrophotometer.
8. Measure and record the absorbance value.
9. Repeat steps 7 and 8 for the other two standards and the filtered bath sample.
10. Plot the true absorbances of the standards as a function of concentration and obtain the equation of the
line that fits the data. This is done in Microsoft Excel
11. Plug the absorbance of the bath sample to obtain the concentration.

If you need assistance you can contact the CHEMEON Tech Center for a spreadsheet that will help process
the data.
Note – these steps describe a basic method for obtaining the absorbance values. Many newer instruments have calibration methods built in. Please consult your operation manual for the correct method of calibration.

Bath Additions:

• Bath replenishment may be accomplished by adding CHEMEON eTCP RTU to the tank.
o Allow the tank level drop by evaporation as necessary and add CHEMEON eTCP RTU directly.
o Bring back to level with DI water.
o Contact CHEMEON Technical Support for further assistance


The Chemetall Chemical Metering Pump can be used to automatically replenish this product. Please contact the Chemetall Process Equipment and Engineering Department for specific recommendations.

NOTES ON USE (See Safety Data Sheet)

Tanks and spray washers should be constructed of virgin, welded polypropylene, alloy 316 stainless steel, or lined with Koroseal or Teflon. Before initial charge, thoroughly clean the tank. For new tanks or liners, rinse surfaces with the acid chemistry of choice for lowering pH, then rinse thoroughly with water. Pumps
and valves should be constructed of stainless steel, preferably type 316L. Suitable plastics such as PP or CPVC may be used for piping and nozzles. Heating surfaces should be Teflon-coated. As with any chemical, the materials described in this document must be used within the recommended operating ranges
for these equipment recommendations to apply.

Avoid contact with or mixing with chlorine-releasing materials.


Prior to handling and use of any of the materials referenced in this document, the Safety Data Sheets should be read and understood by all personnel in contact with these materials.



Product shelf life is 1 year from date of manufacture.


Dry indoor storage at temperatures between 35 °F and 95 °F (1.6 °C and 35 °C) is recommended, away from any incompatible materials referenced in the Safety Data Sheets. All containers should be tightly closed when not in use.


Any disposal of the materials referenced in this document should be in accordance with all applicable federal, state, providential and local regulations. The process solution can contain components other than those present in the materials as supplied. Analysis of process solutions may be required prior to disposal.