Metalworking Fluid Troubleshooting Guide
Here are quick tips for solving the problems with your shop's most
significant liquid asset.
Article From: 3/3/2009 Modern Machine Shop
Metalworking fluids have seen so many technology advances that, among other
improvements, the “Monday morning odor” is probably a thing of the past in many
facilities.
Indeed, as a component of the metalworking process, the fluid is as finely engineered
as almost any machine, tooling or control components that is also vital to making the
part. This sophistication makes it all the more valuable to keep the performance of
the cutting fluid high. Proper maintenance is key to this.
Mike Pelham, a chemist involved in machining and grinding fluid development for
International Chemical Company, compiled the troubleshooting table below. It
addresses both common and not-so-common factors that can affect coolant
performance. In a way, this table is an investment guide, helping shops to realize the
highest rate of return from their most significant “liquid asset.”
PROBLEM
CORROSION
POTENTIAL CAUSES
Too Weak Concentration
Poor Water
Quality/Corrosive Ion
Buildup from Water
High
Temperature/Humidity
Contamination
Corrosive Atmosphere
SOLUTIONS
Adjust and maintain concentration as
recommended by coolant manufacturer.
Use better quality water such as deionized,
reverse osmosis or softened water.
Reduce temperature and humidity and/or
use a supplementary rust preventative.
Identify and eliminate contaminants that
promote corrosion, such as heat treating
salts.
Identify and vent corrosive fumes out of
problem area. Could be from heat treat or
propane forklift truck exhaust.
POOR TOOL
LIFE
Part Handling/Storage
Use clean, plastic dividers to allow parts to
dry and remain separate. For extended
storage, use a supplementary rust
preventative
Too Weak Concentration
Adjust and maintain concentration as
recommended by coolant manufacturer.
Hard water (greater than 200 ppm Total
Hardness) can promote mix instability in
metalworking fluids and lead to loss of tool
or wheel life.
Verify that no changes have been made to
the coolant, tooling or material you are
working with.
Identify and eliminate or minimize
contaminants that promote loss of tool or
wheel life, such as high levels of hydraulic
or way oils, floor cleaners or other coolants.
Adjust and maintain concentration as
recommended by coolant manufacturer.
Some operations, such as high-speed
milling or surface grinding, can promote
foam. Work with your coolant supplier to
implement the product properly suited for
your operation.
Look upstream from operation. What
chemical or lubricant has been in contact
with the part, and how does this impact
foam?
Soft water (less than 100 ppm Total
Hardness) can promote foam in some
metalworking coolants.
Keep the sump full in order to maximize
fluid retention time in sump and allow the
air to come out of the mix.
Check the fluid delivery, filtration system,
and fluid return systems for mechanical
problems and repair them. Kinks in the
hoses or small pinholes may allow air to be
pulled into the system.
Hard water (greater than 200 ppm Total
Hardness) can promote an unstable mixture.
Technology exists to prevent this,
particularly in synthetic products.
Identify and eliminate or minimize
contaminants that promote coolant
instability. These may include tramp oils,
way lubricants or chemicals from a previous
process.
Adjust and maintain concentration as
recommended by coolant manufacturer
Water Quality
Changes
Contamination
FOAM
Too Strong Concentrate
Type of Operation
Contamination
Water Quality
Coolant Level Low
Mechanical Problems
COOLANT
INSTABILITY
Water Quality
Contamination
Concentration
Quality of Water
TACKINESS/
STICKINESS/
GOOEYNESS
Delivery
Contamination
POOR SURFACE
FINISH
Concentration
Coolant Instability
Changes
RANCIDITY
Concentration
Circulation
Tramp Oil
Contamination
Micro-Biological Activity
Hard water (greater than 200 ppm Total
Hardness) can create tackiness in certain
coolants. Your coolant supplier can provide
coolants with blended additives that
naturally soften the water.
Some machining centers may have “blind”
areas where coolant in not in continous
contact. With heat and time the water will
evaporate, leaving a film that will cause
chips to cling. A daily flush of the area with
coolant will reduce this problem.
Identify and eliminate or minimize
contaminants that promote coolant
instability. These may include tramp oils,
way lubricants or chemicals from a previous
process.
Adjust and maintain concentration as
recommended by manufacturer.
When coolants become unstable (see
“Coolant Instability” below), the additives
can be depleted and lead to more rapid tool
wear. This is common for older soluble oil
formulations. Newer synthetic formulations
do not have this problem.
Verify that no changes have been made to
the coolant, tooling or material you are
working with.
Adjust and maintain concentration as
recommended by coolant manufacturer.
Keep it moving. Circulating the tank will
assist with sump life.
Tramp oil can promote microbial growth,
especially in soluble oil formulations.
Implement preventative maintenance
practices to minimize tramp oil. This will
improve coolant life and minimize waste.
If adding water manually, use clean buckets.
Minimize tramp oil and use oil skimmers.
If concentration and other factors are not the
cause, then the use of a tank-side biocide
may be necessary. Advancements in coolant
technology have minimized this. If your
coolant requires this, contact the
manufacturer. A machine cleaner may be
necessary to eliminate bacteria or fungus.