Q&A: Removing Buffing Compound

By: David S. Peterson 24. June 2013

 

Q. I plate high-polish brass parts that have been polished using a buffing compound that reaches high temperatures, resulting in the compound being caked-on. We hand-wipe clean using Stoddard solvent then electroclean, but this cleaning operation becomes very time-consuming as the quantity increases, and it is difficult to meet the customer’s needs. What is the best way to remove the buffing compound? D.H.

 

A. It sounds like your current cleaning method works well, but you are not able to keep up with the demand as the number of parts increases. To introduce more automation into your process, there are two aspects of the current process you will need to replicate. Buffing compounds contain very fine abrasives, often aluminum oxide or silicon carbide, that are suspended in a slurry compound, usually containing some organic components. Your current process is successful since it uses the Stoddard solvent as a cleaning agent to break down and remove the organic component, while your manual wiping method is effective at physical removal of the abrasive component of the mixture.

 

You should address both of those aspects in your new cleaning process. The mechanical component to your current cleaning process will be best replicated by replacing it with another mechanical process such as ultrasonics or agitation of the cleaning tank. Ultrasonics may require a higher initial investment, but could produce quicker and more effective results. The agitated tank would enable you to quickly move the parts through the wash solution or move the wash solution over the parts.

 

In the case of ultrasonics, you may want to consider changing the cleaning solution to a fully formulated aqueous cleaner. There will be surfactants that can break down the organic additives of the buffing component and solubilize water-based additives, and contain ingredients to suspend some of the fine-particulate abrasive so it will not redeposit back onto the part. Ultrasonics would provide the mechanical means you are looking for, and aqueous cleaners tend to be more effective in ultrasonics than organic solvent. This process would be most effective in a heated wash tank that will shorten the time for the cleaner to break down the buffing compound. Finally, an effective rinsing step would be necessary to remove the cleaner and any particulate still adhering to the surface. That could also be a heated, ultrasonic tank, or simply an ambient-temperature, still tank if the parts are coming out fully clean from the first stage.

 

A simpler agitated immersion tank (or spray-under immersion) may still use the Stoddard solvent as long as you are effectively handling the health and safety aspects of the system such as proper ventilation and handling of a combustible solvent. 

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Cleaning Q&A: In-Line Cleaning Machine

By: David S. Peterson 6. March 2013

 

 

Q. I am looking for in-line parts washing to put at my stamping press. The parts are very light and delicate. I am currently talking with one company about its mini-tunnel sonic machine, because I believe that a conveyor system is the way to go. Do you know of other companies that have this type of system? M.A.

 

 

A. One-piece parts handling is thought to be the most efficient if you can correctly coordinate with the balance of your manufacturing process, and it sounds like you have a good plan for yours. The company you mentioned has been in the industry for quite some time, but if you are interested in talking with additional suppliers before making your decision, I suggest you visit the PFOnline Supplier page to find other potential equipment manufacturers that could suit you. Go to PFonline.com, choose the Supplier tab, then the Cleaning & Pretreatment category, and then Parts Washers. 

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Ask The Expert: Clean Paraffin Wax Die Lube

By: David S. Peterson 13. June 2012

 
Q. We are a general purpose coating house. Our cleaning line consists of an alkaline cleaner, city water rinse, iron phosphate, sealer, RO rinse then RO halo. This is a spray system with roughly 45 sec dwell time. The cleaner temperature is 120°F. We are looking at a project involving a cast aluminum valve cover where the die lube is a paraffin wax. How do you recommend we clean the wax from the substrate and have a thoroughly cleaned casting? We end up powder coating the part and have had adhesion failures at different locations. S.M.
 
A. In general, you are doing many things right with your cleaning and pretreatment system, but there could be a few areas for improvement. In general, paraffin waxes need a significant amount of temperature and time to be removed in an aqueous cleaning system. In an ideal situation, you could allow the part to spend more time in the cleaning stage (at least two or three minutes). Additionally, if you could turn up the cleaning temperature to about 160°F, you would stand a much better chance of removing the paraffin wax.
 
However, not knowing what percentage of your overall production is dedicated to this one part, it may be difficult to modify the time and temperature of this one stage in order to accomplish this. If the part represents a relatively low amount of your overall production, you may want to consider a dedicated single-stage, heated immersion soak tank. Immersion cleaning systems can be used even hotter than spray cleaning systems, and parts can be immersed for a significantly longer period of time. Following that initial soak tank cleaning, you could then continue by processing it in your iron phosphate pretreatment and powder coat system.
 
Finally, whenever pretreating any castings prior to paint or powder coating, it may be advisable to pre-heat the casting to the cure temperature in order to outgas any contaminants from porosity that is inherent with virtually all castings. Even the most thorough cleaning job will not eliminate casting outgassing from porosity that can blemish an otherwise perfect coating job.

Ask The Expert: Corrosion Under Powder Coating

By: David S. Peterson 24. February 2012

 

Q. We’re facing problems in powder coating on sheets of cold-rolled closed annealed parts. We found that, after some days, the color is peeling off, and we have found corrosion beneath that. We do a three-in-one cleaning process and then powder coat at our job shop. Our product is an acoustic enclosure of a diesel generator set, so we are using polyester powder for sun resistance. Is there a solution, or should we switch to another process? T.S.

A. Given your description, the problem is not with the paint type or application, but seems to be related to your pretreatment process. You need to consider if the three-in-one sort of pretreatment is adequate for your product performance. That type of pretreatment will clean and coat in the first step, followed by rinsing and then a seal or passivating rinse. That first stage is formulated to only remove light-duty lubricants and soils. If you have heavy lubricants or a significant load of soils to be removed, this type of pretreatment isn’t suited for your requirements. It is imperative to remove all the contaminants, since that is necessary to expose the substrate for subsequent conversion coating in the same step. 

If you have anything except light-duty lubricants, I would suggest you consider working with your chemical supplier to evaluate the possible improvements you could realize through the use of a full five-stage cleaning and conversion coating system. With this scenario, you will have much more flexibility to use a more heavy-duty cleaner that will adequately clean your surfaces prior to the third stage of conversion coating. If even greater pretreatment corrosion protection is necessary, you would then have to consider a zinc phosphate conversion coating process that may include more than the traditional five steps of an iron phosphate process.

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