METAL FINISHING EQUIPMENT

CHEMICAL SOLUTIONS

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Metal Cleaning

On any metal finishing process line production will cease if all of the oils, coolants, machining fluids, drawing compounds, buffing compounds, inks and rust inhibitors are not removed from the surface of the parts.  A clean and active surface is necessary for nearly all finishing operations. One common misconception is that “soap” is “soap”, or that all cleaners are the same.  There are acid based and alkaline based cleaners, oil-splitting and oil emulsifying cleaners, silicated and non-silicated cleaners, phosphate and non-phosphated cleaners, cleaners designed for light metals like aluminum and magnesium, and heavy duty cleaners for cleaning steel in high production. Since most finishing shops have no idea what is on the parts they receive, they require robust cleaners that will remove the widest range of oils and soils without attacking the substrate. Often times laboratory testing is required to determine the best cleaner for an application.        

The most common cleaning or pretreatment cycle for steel includes a soak cleaner, an electrocleaner and an acid pickle tank.  The soak cleaner is formulated with a high level of surfactants or “soap” to remove any dirt and all surface oils, either through emulsification which holds the oils in solution or by splitting and mechanically removing the oil from the cleaner with the use of a skimmer or coalescer. 

The electrocleaner is formulated with a high level of caustic which helps to carry current; parts are chemically scrubbed using“reverse current” which means the parts are anodic or positively charged.  Electrocleaning is an efficient way of removing smut or loosely adherent scale as well as any remaining oils or soils. 

The acid pickle is designed to remove surface oxidation(rust) and any carbon scale from heat treating or welding.  The acid pickle creates a clean and active surface that will quickly flash rust if left exposed in the air, so subsequent operations such as plating, black oxiding, phosphating and painting should follow quickly after rinsing.   Acid additives are commonly used to inhibit the attack of the steel, reduce the iron build up and improve the cleaning ability of the acid. If oil is drug into the acid tank it will lay on the surface and redeposit on the parts as they are removed from the tank, unless there is a surfactant based additive present. 

Cleaning steel is far different than cleaning all other non-ferrous (non-iron containing) metals. Aluminum and zinc die castings will dissolve rapidly in highly acidic and highly alkaline solutions, so mildly acidic or mildly alkaline or neutral cleaners are frequently used.  Copper can be cleaned in “steel type” cleaners, but the alkalinity will cause the surface to darken, so typically a sulfate based acid or a bright dip will follow to brighten and activate the surface. Depending on the surface condition, copper and brass respond well to acidic cleaners as they can brighten and activate the surface in a single step. 

Cleaning parts prior to bulk processing require specialized cleaners.  Cleaning specialized alloys for the aerospace, medical and military industry require even more advanced technology.  Cleaners for the aerospace industry often require highly specialized formulations that will effectively cavitate during ultrasonic cleaning, that will remove oils from unique alloys without attacking the substrate, and that will not foam under extreme agitation.  Petroferm manufactures these types of cleaners as well as environmentally friendly solvents that out perform regulated and banned solvents.  

The technical sales engineers at JSA have numerous options when it comes to recommending a cleaner.  Each chemical manufacturer (Coventya, Metalline, Pavco, etc.) that JSA represents has their own formulations with years of experience, test data and customer testimonials to offer.  Please click here and answer a few questions that will help us determine the best product for your application.  Thank you.