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Guidelines for Selecting Additives in Metalworking Fluids

November 01, 2013
Dr. Neil Canter
Online Only Articles


Metalworking fluids are one of the most complex types of lubricants used. Formulators are challenged to work with as many as 13 different component types that range from antimicrobial pesticides to reserve alkalinity boosters (amines). The most complex types of metalworking fluids are water dilutable and can contain as many as 20 components.

With many different additive choices and a myriad of applications, the selection process needed to pick the right additives and then develop a formulation in which all of them are stable is very difficult. Compounding the problem is that once the formulation is prepared, it must work in the specific application under potentially difficult operating conditions and meet the health & safety guidelines of the specific end user and the region where the end user is located.

The purpose of this webinar to be given in March, 2014 is to shed light on the options available to formulators in a number of important additive categories. Among the categories to be discussed are emulsifiers, extreme pressure additives and reserve alkalinity boosters.

Emulsifiers are divided into two main categories: anionics and nonionics. Anionics such as sodium petroleum sulfonates have been widely used in the past because of their good cost performance. The problem is that anionics are susceptible to foaming if soft water is present, decomposition in hard water conditions and microbial contamination.

Moving to nonionics such as alcohol ethoxylates is a potential option but then the formulator is faced with concerns about waste treatment. In addition, health & safety factors can be present including those that are now becoming apparent as the metalworking fluid industry becomes compliant with the Global Harmonized Standard (GHS).

An example of a nonionic surfactant that is facing concern from a regulatory standpoint is nonyl phenol ethoxylates. This type works well but has been identified as an endocrine disrupter that can possibly cause reproductive disorders.

Extreme pressure agents are selected mainly from the chlorinated paraffin, phosphate ester and sulfurized additive classes. The regulatory concerns with using chlorinated paraffins particularly in the US will be reviewed with options provided to the formulator about what types will probably be available in the future.

A third additive class to be discussed is reserve alkalinity boosters which are mainly alkanolamines. While amines such as monoethanolamine and triethanolamine have been dominant in the marketplace, the industry is now turning more to the use of amines that work synergistically with antimicrobial pesticides to boost the bioresistance of metalworking fluids. Given that there are many choices, formulators must take care to ensure that the proper types of amines are used to provide performance yet also is compliant if they form salts with acids in most of the commercial databases used in the main markets such as the US TSCA inventory. 

GHS will be a focus with compliance in the US and the EU for metalworking fluids barely one year away (end of May, 2015) from the time the webinar is presented. Key metalworking fluid additives that need to be evaluated by formulators will be discussed along with options that can be provided to minimize the presence of hazardous statements and pictograms on labels and safety data sheets.

Dr. Neil Canter is the owner of Chemical Solutions and member of STLE. You can find his contact information in our member database. He will be teaching in the upcoming Metalworking Fluid Management Certificate Course, and will also be teaching in our MWF courses at the 2014 Annual Meeting to be held in Orlando, FL: MWF 125: Health, Safety & Introduction to GHS, and MWF 130: Metal Treating, Cleaning & Protecting Fluids.

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