Passivation, Impregnation, & Abrasive Blasting

Casting porosity has always been a problem. Whether caused by internal shrinkage, gas cavitation, oxide films, or inclusions, the resulting sponge-like internal structure of the otherwise sound metal part can result in leakage of fluids and gases, plating defects, decreased machinability and increased scrap…unless properly treated.
 

Impregnation in metal castings and powdered metal parts seals leaks resulting from porosity. The liquid impregnating material is introduced into the voids within the wall of the part using vacuum and pressure. The material is then solidified, making the part pressure tight.
 

In addition to sealing parts for pressure applications, impregnation improves plating or finishing and can extend tool life.
 

Porosity in metal parts may be classified in two ways: macro-porosity in which large flaws in the part are visible to the naked eye; and micro-porosity which is very small, almost invisible voids. Modern impregnation technology permanently seals either micro- or macro-porosity.
 

Used on all ferrous and nonferrous metals including die castings, sand castings, investment castings, pressure castings, powder metal parts and forgings or weldments, impregnation adds value to metal parts. Metals which may be impregnated include bronze, iron, aluminum, zinc, magnesium, steel and alloys of these metals. Non-metallic materials including plastic, wood and ceramics can also be impregnated.
 

The United States Department of Defense has established various military specifications which outline impregnating requirements. Aero Metal Finishing is certified to current impregnation standards- MIL-STD-276 and MIL-I-17563 which are the basis of many aerospace, automotive and general industry requirements.
 

PASSIVATION
Passivation is a process that employs either nitric acid and water or nitric acid and sodium bichromate and water for use on austenitic, ferritic, martensitic or precipitation hardened corrosion resistant steels. The Passivation process is used for removing embedded iron particles from the surface of stainless steel alloys.
 

ABRASIVE BLASTING
Abrasive blasting is used to remove heat treat scale, contamination and surface defects. It is also used as preparation of surfaces prior to painting and plating. Glass bead and aluminum oxide are used for general descaling and rust removal.
 

Call us today to discover how Impregnation Technology can add value to your metal parts, eliminate leakage and prolong tool life.