Metalworking fluid problems - Corrosion

4 most important causes of corrosion in your process

Water composition

Chemicals in the water used to make the metalworking fluid may have a negative impact on corrosion resistance. Water contains ions, some of which can be aggressive, facilitating corrosion. 

Specific threshold values have been established for these ions in the water. If the water exceeds these values, it is considered corrosive. For example, several well-known corrosion parameters include chloride at greater than 100 ppm, sulphate at greater than 100 ppm or nitrate at greater than 50 ppm. Chloride, sulphate and nitrate are substances that reduce or nullify the protective properties of your metalworking fluid. 

Many of the beneficial properties of metalworking fluid can literally be destroyed by chemical reactions with dissolved solids in the water. The best-known example of this is the effect of "water hardness", which is essentially the concentration of calcium and magnesium in the water. Hard water is water that contains more than 250 ppm of calcium carbonate. The "harder" the water, the more susceptible the fluid is to being corrosive.

Conductivity is another way to quantify the amount of dissolved ions in the mixture. Higher conductivity promotes corrosion, mixture instability, residue formation and other problems. Conductivities greater than 4000 microsiemens per cm are considered high, but in some production processes, even higher values occur without causing corrosion problems. 

Will-Fill informs you, before it's too late, when the conductivity exceeds the desired level. That way you can take timely actions to prevent the situation from worsening.

Bacterial control 

High levels of bacterial growth in the metalworking fluid can cause it to separate, reducing or completely nullifying the corrosion-resistance properties of the fluid.

In the case of ferrous, or iron-containing, metals, it is important to keep the pH above 9. With non-ferrous materials, on the other hand, this pH will have a negative impact on corrosion resistance. 

Mixing ratio

The components of metalworking fluids are designed to be effective within a specific dilution range. If the fluid is more dilute than the range specified, the 'thinned out' components of the fluid may not be capable of achieving the intended results. This is also true of rust inhibitors, which, if too dilute, will likely not be capable of protecting the newly ground or processed parts from corrosion.

Will-Fill automatically maintains the correct mixing ratio, completely taking over the work of monitoring it.

Bimetallic corrosion

Bimetallic corrosion is the corrosion of two different metals that are in contact with one another. Bimetallic corrosion occurs when electrons from one metal transfer to the other metal, where the metalworking fluid acts as a conductor. That is why it is important to ground all residual currents, so that no current of electrons can flow through the metalworking fluid.

One of the most important, if not the most important, causes of corrosion is the chemical composition of the metalworking fluid relative to the material being processed. Certain processes are more susceptible to corrosion, but a poor mixing ratio and contamination by foreign substances can also have an effect on whether or not corrosion occurs.