-- The Home Page of the Finishing Industry
23+ years of serious education, promoting Aloha,
& the most fun you can have in metal finishing smiley
    no popups, no spam
on this site
current topics
topic 10088

Can't Raise Temperature of Black Oxide tank enough

Help. I have a 250 gallon tank for a black oxide operation. It is gas fired and has caused me no problems.

The problem... the last three days I have not been able to get the temperature of the tank above 270 F. I have added an extraordinary amount of Black Oxide to the tank thinking that my mixture was off. To no avail. The temperature has remained at 270 F. It has not mattered how much salt I have added the temperature will not increase. I have checked the burners and they appear to be functioning well. I have checked the temperature controller and thermocouples and they are also fine.

What next?

Terry Murphy
- Bridgeport, Connecticut, USA


First off, be really, really careful with this problem. Remember that water boils at 212 degrees F, such that a sudden unanticipated mixing of a slug of water with a slug of 270+ degree solution can cause the water to flash to steam and make the tank erupt.

I don't think I would attempt to troubleshoot this problem except wearing head-to-toe protection.

But what I would do is take a small beaker of the solution into the lab and heat it under a hood there. This will tell you whether the problem is that your gas burners are not producing enough heat, or that the boiling point of the solution is 270 degrees so that it is impossible to get it hotter.

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


Terry -

First double check your temp probe using a mercury thermometer. Secondly, adding more salt to the bath makes the boiling point rise even higher, so it will take even longer to get to the operational point of the bath. Another possibility is that you have a sludge build-up on the bottom of the tank that is insulating the bath from the heat source - try scooping the bottom to see if there is an unusual amount of sludge present. Occasional rectifying helps to minimize sludge formation.

Hope this helps.

Dan Brewer
chemical process supplier - Gurnee, Illinois

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

ADD a Comment to THIS thread START a NEW threadView CURRENT TOPICS

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.