Zirconium Oxide Pretreatment for Military Coating Systems
The U.S. Army Research Laboratory ( ARL) continues to demonstrate zirconium pretreatment technology as a replacement for existing aluminum and steel pretreatments at military depots. A third demonstration of the zirconium oxide technology, using PPG Industries X-BOND™ 4000 zirconium pretreatment, was carried out at Anniston Army Depot. Previous demonstrations, under ESTCP Project WP-201318 were conducted at Letterkenny Army Depot and Marine Depot Maintenance Command–Production Plant, Albany.
The Anniston demonstration included a deoxidation step for aluminum, which was developed to provide enhanced performance in galvanic cyclic corrosion testing. The demonstration showed that, in addition to lowering environmental and personal safety risks, the zirconium process reduces the number of steps to pretreat steel parts. A comparison of the processing steps for Zirconium Pretreatment vs Zinc Phosphate (steel) and Hexavalent-Chromium (aluminum) is depicted below. Unlike the incumbent processes, the zirconium pretreatment step is carried out at room temperature, which reduces energy requirements.
The primary benefit of the zirconium process is the use of a single pretreatment bath for both ferrous and aluminum substrates reducing the footprint required for pretreatment processing, thereby providing greater latitude in scheduling multiple metal substrates. This single process line allows the zirconium technology to apply pretreatment to both ferrous and aluminum substrates and becomes an alternative to both zinc phosphate with chromate post rinse for ferrous substrates and chrome containing, both hexavalent and trivalent, conversion coatings for aluminum.
Performance testing, including laboratory accelerated corrosion testing and seacoast environmental testing, of the demonstration parts and panels from the three demonstrations have confirmed that the zirconium technology provides performance that is equal to both zinc phosphate and the aluminum conversion coatings. Due to the performance of this technology, we anticipate this will qualify to both TT-C-490, Chemical Conversion Coatings and Pretreatments for Metallic Substrates (Base for Organic Coatings) and MIL-DTL-5541 Chemical Conversion Coatings on Aluminum and Aluminum Alloys. The new type that will be included in MIL-DTL-5541 for non-chrome technologies will be initially reserved or Army assets only. Qualification to these specifications will allow this technology to be transitioned into DoD facilities.
The image below shows an aluminum engine part being pulled from the rinse after treatment with XBond™ 4000 during a demonstration of the Zirconium Pretreatment at Anniston Army Depot.
X-Bond is a trademark of PPG, Inc.