POROUS CHROMIUM DEPOSITS HAVE GREATER WEAR RESISTANCE OWING TO THEIR ABILITY TO RETAIN OIL.
TWO DISTINCT TYPE OF POROUS CHROMIUM ARE PRODUCED.
1.PIT TYPE USED FOR ALL TYPE OF ENGINES.
2.CHANNEL TYPE USED FOR AIR CRAFTS.
THE MOST WIDELY USED TECHNIQUE HOWEVER INVOLVE CHEMICAL OR ELECTROCHEMICAL ETCHING OF THE CHROMIUM DEPOSIT AFTER PLATING,THE ETCHED SURFACE IS FINISHED BY POLISHING OR LAPPING.
HOWEVER USING PROPRIETARY SOLUTIONS BY VARYING THE OPERATING CONDITIONS MICRO CRACKING IS ACHIEVED.
BEST DEPOSITS TYPICALLY MAY HAVE 800 TO 3000 CRACKS PER LINEAR INCH.
POROSITY FERROXYL TEST:- POTASSIUM FERRICYANIDE,NACL
THE FERROXYL TEST IS USED TO EVALUATE THE POROSITY OF CHROMIUM DEPOSITS ON STEEL SUBSTRATES.AFTER BEING DIPPED INTO THE TEST SOLUTION A FILTER PAPER IS PLACED OVER DEPOSIT.THE FILTER PAPER IS REMOVED AFTER SOME TIME WASHED AND DRIED ANY PORES SHOW THEMSELVES AS BLUE SPOTS ON TEST PAPER.