Steel contamination was causing clogging and blocking during the process of electrophoretic deposition. (Image: Artigone Pumsirisawas /Shutterstock)
Steel contamination was causing clogging and blocking during the process of electrophoretic deposition. (Image: Artigone Pumsirisawas /Shutterstock)

Electrophoretic deposition is a key process in the manufacture of pick-up truck frame production. However, for one Thai automotive company, steel contamination during the process was causing clogging and blocking. A UK manufacturer and designer of high performance magnetic systems offered filters which reduced contamination and extended machinery life.

The process of electrophoretic deposition consists of several dip tanks, starting with the pre-treatment tank and ending with the electrophoretic deposition tank. The manufactured pick-up truck frames from the assembly line are then sent to a separate area to be thoroughly cleaned and then receive a final coating treatment using the electrophoretic deposition process to finish it all off.

The first two dip tanks that the pick-up truck frames are introduced into are pre-treatment tanks, each with a volume of 66 m3 and both positioned on the ground. They are filled with de-greasing liquid, which is a water-like strong alkali solution with a pH of approximately 9. Both tanks are fitted with a barrier filter and a centrifuge filter to remove contamination that has been washed off the pick-up truck frames.

Clogging and blocking

However, the barrier filters and centrifuge filters used by ISUZU Motors Co. Ltd in Samutprakarn, Thailand, were ineffective, and very quickly became overwhelmed by the build-up of contamination, causing them to clog up and block. As a result of this, the filters could not satisfactorily remove the fine steel contamination from the pre-treatment liquid, which resulted in the particles being carried over into the electrophoretic deposition tank.

As a result, the pre-treatment tanks had to be emptied and cleaned on a regular basis, causing machine down-time and delays to the production process. Eclipse Magnetics has supplied ISUZU Motors Co. Ltd in Thailand, with two of its high performance magnetic filters; an AutoMag Skid and a FiltraMag, to reduce contamination in electrophoretic deposition dip tanks.

The company supplied an AutoMag Skid AM12S1-8, including a pump, sump tank, and secondary return pump. This self-contained magnetic filtration and fluid recovery system is fully automated and maximizes collection capacity. The automatic nature of the AutoMag skid ensures that there is no production down-time, resulting in a very efficient production process.

The Automag Skid effectively removes magnetic and para-magnetic contamination from coolants and lubricants down to submicron size. Contaminated fluid enters the inlet port where it is dispersed into the first filtration chamber. The fluid passes around the high-intensity ‘rare earth’ magnetic cores where contamination particles are removed, until the fluid is slowed and then enters the second filtration chamber where it receives further filtration. Contamination remains attached to the stainless steel sleeves of the cores whilst the filtered fluid exits through the outlet port.

Purging & recycling

The purging process is fully automated, with the cores being raised from the sleeves and the purge valve switched. Fluid is pumped through the filter, washing the contamination from the stainless steel sleeves and carrying it into the buffer tank. The fluid is then slowed and passed onto the coolant roller. This purged fluid is highly contaminated, but the flow rate and high magnetic strength of the roller ensure that contamination removal is extremely efficient. The clean fluid is then re-circulated, the contamination is scraped from the roller, and then collected for disposal or recycling.

Further filtering

In addition, a single FiltraMag 2.5 was installed before the centrifugal filter to ensure that almost 100% of the contamination is removed. The FiltraMag is inspected and cleaned; a simple, quick process. It can also be removed and cleaned while the machine is in operation. The 11,000 gauss magnetic core pack ensures that the contamination is removed on first pass through the filter. High intensity magnetic cores ensure particle filtration down to sub-micron size, ensuring that the fluid is fully filtered and so eliminating problems.

Since the introduction of the filters, steel contamination is no longer found in the electrophoretic deposition tank at ISUZU Motors, and significant cost savings have been made by extending fluid life, reducing down-time and filter costs, and extending machinery life.

Manoon Sihsobhon, from Huat Seng Co Ltd, distributors of Eclipse Magnetics filtration products in Thailand, said: “Currently, one five gallon pail of steel contaminant is being removed from the AutoMag Skid AM12S1-8 every three weeks.

Although steel contamination is present in the pre-treatment tank, the overall quality is much improved; so much so that steel contamination is no longer found in the electrophoretic deposition tank. The level of contamination concentration has significantly improved since the installation of the AutoMag and FiltraMag.”