The Lubricant Switch

Question:

I recently switched metalworking lubricants in my forming operation. I went from a regular oil to one that was recommended by a salesman from a different company. That salesman claimed that his recommended lubricant would be much easier to clean off the parts since it is diluted with water. The demonstrations he gave showed it to clean off some sample parts very easily, but now that we are in full production with their lubricant we have found it more difficult to remove and also noticed staining. We now have a new salesperson, and he has not helped us since the conversion. Can you let us know what has happened with this lubricant? K.P.

Answer:

I would have initially suggested that you contact the salesperson that sold you on that lubricant and get him to explain to you what the problems are. Since he is no longer with the company you are doing business with, it is not as easy. I would suggest, though, that the new salesperson get up to speed on the particular lubricant as quickly as possible. He should also have technical people within the company at his disposal that can aid in diagnosing the problem, even if he is not that experienced in it.

It sounds to me as though the salesperson did not take your entire process into consideration before making his recommendation. You mentioned that the lubricant is diluted with water. Considering this and your other comments, I assume you are working with a soluble oil. This is an oil that appears to be an ordinary mineral oil right out of the drum. The difference is that it is cut with water when used. The reason for this is that it can offer the benefit of a mineral oil, but is cut with water, which can make the as-used cost of the lubricant less. Additionally, the water provides good cooling capacity to the tool. Finally, the lubricant is relatively easy to aqueous clean if done so in a fairly short time after forming. Short is a relative term here, but would roughly mean hours, not days or longer, of the lubricant remaining on the surface of the part.

In the working sump, the lubricant is a mixture of oil and water, with water usually making up at least 50% of the mixture. The lubricant is formulated with surfactants that will suspend the oil in the water to make what is known as an oil-in-water emulsion. The reason for the problem with prolonged storage is that as the part sits prior to cleaning, more and more water is evaporating from the lubricant film. As it evaporates, it eventually reaches a point where the emulsion inverts and forms a water-in-oil emulsion. This will further dry down to form a tacky residue that is difficult to remove from the surface of your parts.

Regarding the staining, it is likely that the lubricant contains additives that increase the lubricity of the package making it a more effective lubricant, allowing it to work with different metals over a broader range of operating conditions. The drawback is that if left on the surface of the part for an extended period of time, it can actually attack the part, especially in areas of higher concentration (sections where the lubricant may have pooled for instance).

If possible, the storage time of parts needs to be decreased in order to adequately clean them and eliminate these problems. I am guessing that when the salesperson performed the demonstration, it was on a part right out of the press, if he even did that much. It is my experience that the salesperson wants to simply apply lubricant to a part and then quickly clean it to show how “cleanable” it is. In reality, almost no lubricants are cleaned in the “as-mixed” condition and go through moderate or severe degradation due to the heat and pressure of the metalworking process.

Note: the following question was posted on the PFOnline Cleaning and Pretreatment Forum. An excellent way to tap into the knowledge of some of your peers and colleagues who may have had similar experiences, go to the web site at www.pfonline.com and click on the Forums tab.