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Internal hydraulic tank rust prevention

Q. What is the best way of prevention of hydraulic tank contamination?
What coating we have to use to achieve better oil contamination level?

sagar banekar
engineer - belgaum, India
August 23, 2023

Q. We are a large scale manufacturer of heavy duty industrial mowing equipment. We manufacture our own hydraulic tanks. We have an ongoing problem with the tanks having water build up inside the tanks due to condensation. This can happen in as short a period as a week when the tank sits in our yard or a dealers yard. The water causes the tank to rust inside and thus contaminates the hydraulic fluid when the tank is filled. We cannot ship the tanks filled with the hydraulic fluid. The tanks are made from cold rolled, 1018 steel. The inside of the tank is not accessible for cleaning after the tank is assembled and it is extremely difficult to access as just the weldment. I am looking for suggestions on how to prevent water from condensing inside the tank and/or methods to prevent the tank from rusting inside.

Reagan S. Hill
industrial mowing equipment - Seguin, Texas

A. Dear Sir:

I think you need to cold zinc galvanize the tank by filling with liquid zinc compound when the tank is first finished. My experience is in galvanizing a hydraulic tank in plastic injection machinery with the same problem.

Otherwise put dehumidifier equipment on the top of the tank, same as a pipe and the water will condense on the cold tubes from the dehumidifier; this system works fine. The secret is to put the equipment over the oil in a pipe compartment on top, and the water will be continuously drained on the bottom of the pipe compartment.

Good luck,

Carlos Koch
- Guayaquil, Ecuador

A. Can't you just blow a good amount of dried air inside the tanks to evacuate the humidity and cap them?

Guillermo Marrufo
Monterrey, NL, Mexico

A. The only sure way to prevent condensation in these tanks is to eliminate the thermal differential transfer. In other words, eliminate the opportunity for condensation to form by eliminating the temperature difference with a thermal insulating paint. If the tank is rusted on the exterior, power wash it. Apply a rust stopping primer over the tank exterior. Let dry for a day and then apply the thermal insulating coating. Allow to dry, then top coat. This will stop your condensation problem and extend the service life of the tank by many years.

Jeffrey Larson
commercial coatings - Houston, Texas

A. The cause in condensation in the tanks through the breather. Check out "desiccant breather caps". Understanding where the contamination (moisture) is entering the system is half the battle. With the desiccant breather it removes all the moisture; it is an important part of any preventive maintenance. Remember, any coating will leach into the system and cause problems. Hope it helps.

Mike ONeill
- Downingtown, Pennsylvania
September 7, 2009

A. Dear Sir,

The reservoir you have is allowing condensation to build up inside the reservoir due to the constant changes in outside temperatures which are also changing inside the reservoir. The only way to keep condensation out is stopping it from getting in. In this case you will need to add a desiccant breather to the reservoir. We use these on ALL of our hydraulic reservoirs that are in extremely humid areas and it keeps the water content out of the oil. Any openings in the reservoir should be plugged and allow only one breathing point that is supplied by a desiccant air breather. Or, you can have many as long as they have desiccant breathers.

Kevin Barnidge
fluid reconditioning - Columbus, Ohio
December 1, 2012

Trap Breather

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A. Another point to make is that you have to make sure the Cold rolled steel is pickled. This conditions the steel and keeps it from delaminating, etc. Some people have tried rust inhibitors sprayed in the tanks to help them with shelf life prior to installation. Beyond that the use of a proper breather that removes the moisture from the air during draw down is the only way to help with that. Donaldson makes a good one called a Trap Breather. Just FYI.

Buck Schmitt
- Pennsylvania
March 22, 2023

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