Impregnation: Preventing Leaks, Improving Looks and Increasing Profits
Filling porosity prior to finishing dramatically reduces reject rates.
“Out, damned spot, out I say!”
What metal finisher hasn’t thought of Lady Macbeth’s famous soliloquy at some time? The incantation didn’t work for her, and it doesn’t work for metal finishers either. Spotty, flaking, bubbling, cracking or peeling finishes are seldom caused by the witches of Macbeth, but more frequently caused by a more insidious problem: porosity.
Poor plating, painting, anodizing or other coating problems costing untold dollars to metal finishers are frequently vastly reduced or eliminated by the cost-effective preprocess of impregnation.
As metal parts become end products, their value increases at every manufacturing step, especially in the finishing processes. Consequently, rejection of finished components late in the production cycle due to blemishes such as spotting, bleed out, coating bubbles and surface inclusions cost much more than rejection in an “as cast” or raw state. Why?
For castings, re-melting—while costly—allows the caster to reproduce the parts for little more than the cost of energy, generally only a small percentage of the raw part value. With weldments or brazed assemblies, the same is true: returning to the previous step is economically possible. As parts move to finishing, it’s an entirely different story. Finishing costs (polishing, plating, cleaning, coating and so on) are cumulative, and make parts progressively more valuable. They can account for half or more of the parts’ value and this investment is completely lost if parts are discarded or reworked.