Testing whether Alodine 1200 clear finish was actually done

A. You might want to check your information again, there is no such thing as a "clear Alodine 1200" coating. Alodine 1200, 1200s and 600 are all MC (multicolor coatings) chem films. If you requested 1200, you will get a colored coating. If you requested clear however, you will get an Alodine 1500 or an Alodine 1000 (these are CC, or colorless coatings). There is essentially no way to non-destructively verify the coating unless you have access to the part within 1 hour of the coating process.

You can however check for a proper coating on the assumption that it is coated (i.e. check for a powdery coating, check for areas of color, check for contamination on the surface...), or you can scrap one part and run a test on it to verify the coating. The test is called a spot chromate test and if you want I'll send you the procedure. The area taken for the test is around 3/4" diameter and the test will remove the coating in that area (depending on your specs, you may still be able to accept the part...)

Please respond if you want the procedures for this test, or if you have any other questions on "clear 1200 Alodine" (MC vs. CC).

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Q. I would be interested in the spot chromate test procedures.

Floy A. Smith [returning]
- Fremont, California, USA
2001

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Q. Hi, can I have that procedure for the Alodine test?

Kuo Jing Yang
- Buffalo, New York
October 18, 2022

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Hello Kuo. Benjamin's posting was from two decades ago. However, keep reading, because he came back and he posted his procedure on this page :-)

Luck & Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. We use a chemical spot test kit. It's made by Macdermid. They call it the ARP solution, part A&B.

A. Chromate Spot Test (for QA):

1) 0.200 (± .004) grams of diphenylcarbohydrazide

2) 20 mils Acetone [affil. link to info/product on Amazon].

3) 10 mils H3PO4.

4) 10 mils H2O (distilled).

5) Label and date solution with an 8-hour expiration date.

6) Dispose of expired reagent in the appropriately labeled waste container.

That's the makeup for the chromate spot test. For it to work though, you need to re-activate the chromium on the surface. I do this be wiping the area fairly aggressively with an clean cheesecloth wet with MEK / methyl ethyl ketone, then I lightly abrade the area (1/2"-3/4")with a Scotch Brite [affil. link to info/product on Amazon] wet with MEK.

I've also found that using a pocket knife to scrape off some of the coating (though you can't see it...)into a small beaker (say, 50 mL) and adding 3-5 mL distilled water and testing for chrome will also work sometimes.

If you Alodine at all in-house you can simply t/u the area with a manual application.

Let me know if this helps, or if you need more specific info.