-- The Home Page of the Finishing Industry
A website for Serious Education, promoting Aloha,
& the most FUN smiley you can have in metal finishing

on this site
current topics
topic 0747

Minimum time before handling chromated parts?



We need, due to a tight schedule, to shorten the time between the application of Alodine process and the mechanical use (assembly) of the treated Aluminum parts.

According to ASTM B449-93 [link by ed. to spec at TechStreet] (7.1) the chromate conversion coatings should be "handled carefully for the first 24 hours after treatment...".

QQ-P-416 [link by ed. to spec at Defense Logistics Agency,] ( "require a sufficient period....approximately 24 hours at 70^F to 90^F...".

Do you have any Good Engineering Practice to decrease the drying time?


Asaf Katz


Many shops use a final warm rinse (not over 140 degrees F), followed by a forced air dryer heated by hot water or steam .

Plenty of air, and not much heat, seem key to accelerating the drying without dehydration of the chromate film.

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


During the first 24 hours the chem film coating is drying from a quasi gel film. Care must be taken not to remove this "gel" Hot water above 140, skin temperatures above 220, and handling will disturb the surface. One of the best ways is forced hot air, the higher the pressure the better. Good luck.

Dan Zinman

We found that a couple of hours in direct sunlight (in Florida) really accelerated the setting. My real recommendation is that you start the process one day earlier so that it can set the required 24 hours. It is there for good reasons.

James Watts
- Navarre, Florida


We have an automated process line that produces Alodined parts that are fairly immune to scratches. Parts are dipped into a heated D.I. rinse at 140 deg F. for 20 - 30 seconds and then placed into a drying oven set at 135 deg. F. The Alodine coating will become dehydrated if exposed to temperatures in excess of 140 deg. F. Dehydration of the coating reduces it's corrosion protection, so take care. Also, the heated rinse tends to remove the coating. (referred to as bleaching the part)

Parts with sharp edges still have to be individually wrapped.

Joe D. Allbritten
- Greenville, Texas


I have a question about Alodine chemical coatings in small business. Is there any type of filtration system that allows you to reuse this product to cut down on the amount of hazardous waste that is generated? Our system consists of 1 product tank, followed by a rinse tank. The carry over ends up making the rinse tank as dark as the product.

Any suggestions would be greatly appreciated!

Brad Beckham
- New London, Connecticut

This public forum has 60,000 threads. If you have a question in mind which seems off topic to this thread, you might prefer to Search the Site


Disclaimer: It's not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & Devices

©1995-2018, Inc., Pine Beach, NJ   -   About   -  Privacy Policy
How Google uses data when you visit this site.