Attachment 0031 - Alternate Materials.doc

Alternate Materials

ATTACHMENT 0031

Replacement of hexavalent chrome sealers or post rinses for current zinc coatings.

All substitutes for hexavalent chrome post rinses or sealers for use on electro-deposited coatings of zinc on iron and steel, ASTM B633 or zinc coatings mechanically deposited on iron and steel , ASTM B695, or an approved equivalent zinc plating specifications or standards shall maintain the specified zinc coating thickness as designated on the applicable drawing call-out. Hexavalent chrome substitutes when tested IAW ASTM B117 for 96 hours shall show neither corrosion products of the substitute coating nor zinc nor base metal corrosion products. The appearance of corrosion products visible to the unaided eye at normal reading distance shall be cause for rejection except that corrosion by-products of the substitute coating at the edge of specimens shall not constitute failure. All other specification requirements shall be met. Neither the coating or application process shall alter base metal physical properties or induce hydrogen embrittlement. Final finish colors olive drab or black, if available, are preferred if the color doesn’t interfere with performance requirements.

Hexavalent chrome free finish notes for cadmium replacement and all new fasteners and small parts or replacement for zinc coating/ plating… Finishes and coatings which are hexavalent chrome free and cadmium free may be used on all fastener grades and small parts if they pass ASTM B117 testing at 180 hours with no corrosion products visible to the unaided eye at normal reading distance which shall be cause for rejection except that corrosion by-products of the finish or coating at the edge of specimens shall not constitute failure. After 700 hours of ASTM B117 testing the appearance of red corrosion products visible to the unaided eye at normal reading distance shall be cause for rejection except that corrosion by-products of the finish or coating at the edge of the specimen shall not constitute failure. Neither the coating or application process shall alter base metal physical properties or induce Hydrogen embrittlement. Final finish colors of olive drab or black, if available, are preferred but not required as long as the color doesn’t interfere with end item performance requirements.

Stainless Steel:

Stainless steel may be substituted for fasteners under UTS < 150 ksi, up to grade 7 and for small parts. Stainless steel fasteners and stainless sheet metal parts shall be passivated in accordance with ASTM A967 utilizing a hexavalent chrome free process then blackened with a chrome free process in accordance with best commercial practices. Small stainless plate metal parts may be blasted to NACE #2 or SSPC-SP10, then immediately blackened with a chrome free process in accordance with best commercial practices. Stainless steels which have been pickled and are free of scale, free iron, and exogenous foreign matter do not require further chemical passivation treatments prior to blackening with a chrome free process in accordance with best commercial practices.

Additional Requirements:

Torque and Clamping:

New coating technologies that have been approved to replace Hexavalent chromium and cadmium coatings shall be capable of maintaining torque and clamping values that have been established by the applicable drawing or for that particular bolt grade and diameter. The contractor at his option may apply an appropriate wet/dry lubricant as a means of resolving clamping issues.

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Distribution A – Unlimited; Distribution Approved for Public Release