Haward also offers Chem Film/Iridite, Pickling & Grit Blasting
Chem Film/Iridite or Chromate Conversion Coating
Chem Film is a chemical process that produces a protective chromate conversion film on aluminum and aluminum alloys. Application is by dip, spray or swab, producing coatings that range from clear to dark yellow. The darker coatings provide the greatest corrosion protection. The coating can be used as a final finish and can also serve as a base for paints, high performance top coats & lacquers, or a base for rubber bonding.
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Stainless steel can corrode in service if there is contamination on the surface or if there has been a process that has altered the composition of the surface, usually welding or some other heating process. Unless a fabricator is meticulous with his/her handling of stainless steel, pickling should always be carried out after fabrication for maximum corrosion resistance.
Pickling or acid cleaning restores the corrosion resistance of the surface by removing any surface contamination such as grease or dirt, as well as any embedded iron or exposed inclusion particles in the steel. The most common solutions contain nitric acid, although others are available. Some of the surface contaminants may be removed by grinding or polishing, but sometimes particles of polishing compounds can be embedded in the surface, and hence damage corrosion resistance.
Where welding or any other means, to the point where a colored oxide layer can be seen, has heated the steel, there is a chromium-depleted layer on the surface of the steel underneath the oxide layer. The lower chromium content gives lower corrosion resistance. The layer can be ground off, but it is safer to pickle it off. Hydrofluoric acid must be included in the pickling solution, since nitric acid alone will not dissolve the surface layer. Pickling is best done by immersion in the pickling solution or by using pastes where the solution is mixed with an inert carrier to allow selected areas to be treated.
If you would like to evaluate our Passivation or Pickling capabilities, we will be happy to process samples of a reasonable size and quantity at no charge.
In our facility, aluminum oxide media is delivered using compressed air. Aluminum oxide is more aggressive than other commonly used abrasives.
Haward Corporation has three abrasive blast cabinets and for larger parts a blast room that is 10’ x 15’ x 12’ for those larger items. Items that are too large for Haward to handle are farmed out to approved vendors for blasting.
At Haward Corporation, blast finishing is primarily used for cleaning, oxide removal and surface preparation. Occasionally, it is used to put a satin, frosted finish on parts for cosmetic purposes or to blend various imperfections as well as to achieve a decorative finish followed by electropolishing.