LeDuc uses Surfox to clean and passivate TIG weld.

Custom sheet metal fabricator, R.R. LeDuc Corp. (www.rrleduc.com), needed an alternative method for cleaning and passivating TIG welds on stainless steel. It wanted a method that produced the metal finishes its clients demanded, and required less work than the method it was using. It also did not want to use pickling paste, which contains highly corrosive acids and presents a disposal challenge.

For 37 years, LeDuc cleaned and passivated welds and heat-affected zones made on stainless steel by using wire brushes or non-woven abrasive cloths. This method produced scratches and changed the line grain or matte finish on the metal's surface. Restoring the surface to its original appearance required additional man-hours. As customers increasingly specified stainless steel and required specific finishes such as No. 4 line grain, LeDuc decided it needed to find a less laborintensive way to tackle the job. It enlisted the help of its welding distributor, who proposed a new technology from Walter Surface Technologies (www.jwalterinc.com) called Surfox.

An electrochemical process, Surfox cleans and passivates TIG welds on stainless steel at a rate of 3 ft. per minute using an electrolytic solution — mild phosphoric acid — with a regulated electrical current. This method does not alter the metal's original No. 2 mill finish or change the No. 4 line grains. The Surfox process meets the American Society for Testing and Materials' A-967 standard for passivation of stainless steel, says Dean Gendel, marketing manager for J. Walter Inc. LeDuc uses Surfox Model 202, which cleans and passivates in both AC and DC modes. In the DC mode, welds on stainless steel can be cleaned, passivated and electropolished to a No 8 mirror finish.