Lubricants and Coolants – Effectiveness vs. Cleanability

In order for a lubricant or coolant to be effective it must possess the very properties that make it difficult to remove.  In industrial machining, stamping and metal forming applications, selecting lubricants and coolants wisely can greatly simplify cleaning processes required to remove them once these processes are complete.

Effective lubricants must be able to adhere tightly to surfaces, penetrate, and resist moisture.

Adhere Tightly to Surfaces –

It is the job of a lubricant to remain in position between two surfaces moving relative to one another.   Its presence, in essence, prevents the two surfaces from touching one another directly.  In order to do this effectively, a lubricant must bond to or “wet” the surfaces being lubricated.  Interestingly, soaps and lubricants are closely related.  Remember, the parent of early soaps was lard.  Lard, of course, is a very effective lubricant.  Soaps, in many cases, are also effective lubricants.  We have probably all applied a little soap to a wood screw to “help” it into the wood.  Soaps, like lubricants, bond to surfaces and, because of this, provide lubrication.

When it comes to removing lubricants, the cleaning chemistry or “soap,” if it doesn’t dissolve the lubricant (as will some solvents) must bond more strongly to the surface being cleaned than the lubricant being removed in order to be effective.  As a result, the better the lubricant (as indicated by its superior bonding properties), the stronger the cleaning chemistry must be to remove it.  Although I would not advocate using an inferior lubricant when a better one is needed, I would suggest that using a more effective lubricant than is required for a task only complicates its later removal.

Penetration –

The ability for a liquid to penetrate into small spaces is related to surface tension and viscosity.  Liquids with low surface tension and low viscosity penetrate more effectively than those with high surface tension and high viscosity.  In most cases, the differences between lubricants are primarily the selection of the base lubricant based on its natural surface tension and viscosity properties and other ingredients which are added to alter these properties to maximize its overall performance.  Once again, viscosity and surface tension are also properties of cleaning chemistries.  Although the relationship is not as direct as described in the above paragraphs regarding the “wetting” properties of a lubricant, there is still a direct correlation between the ability of a lubricant to penetrate and the difficulty of removing it.  In essence, the cleaning chemistry must be able to penetrate more effectively than the lubricant for removal to be effective.

Resist Moisture –

Most industrial lubricants are designed to resist moisture.  Some may be quick to point out that most “coolants” are composed primarily of water.  This is absolutely true, BUT, the purpose of the water is to provide cooling, not lubrication.  Lubrication is provided by lubricants that are mixed with or emulsified in the water.  These lubricants might not be as effective if they were totally dissolved by the water component of the coolant.  Again, in order to be effective, cleaning chemistries must include components which enable them to more effectively emulsify lubricants than those used to stabilize the lubricants in the coolant formulation.

In summary, a successful manufacturing process must carefully match lubricants and cleaning chemistry.  This can be difficult, especially when a number of processes are being performed in a facility sharing a single cleaning system.  Any change in lubricant or cleaning chemistry should be approached carefully with due consideration for any interactions that may result from a proposed change.

–  FJF  –