Process No. CELCO – 1008
Revision A: Dated – February 13, 1997
Para 22.214.171.124 – Revise first sentence to read “The electrolyte fluid specific
gravity, 1.750 +/- .020, is extremely important to the
Para 126.96.36.199 – Replace the sixth sentence with “If pitting of finish occurs,
decant with new fluid to bring solution back to appropriate
Para 7.1.3 – Revise first sentence to read “This fluid is a 30% – 50%
Nitric Acid Bath.” Add new sentence to read “Fluid level
will be controlled using equal strength fluid.
Revision B: Dated – October 28, 2008
Add approval signatures and dates.
page – i –
1.1 This procedure will define the various steps involved in electropolishing
components for use in Learjet, Inc. applications.
2.1 The material used in these components will be 300 series stainless steel
alloy, or of a chromium/nickel alloy suitable for electropolishing.
2.2 The components will be in a prefinished state with the surface to be
electropolished having a surface roughness no more than twice the
roughness of the desired finished roughness.
2.3 All components will be assumed to be clean and absent of all scale, oil or
surface film upon receiving.
2.3.1 If components are received with scale, oil or surface film. The
parts will be cleaned using the following procedures.
188.8.131.52 Soak parts in commercial grade Acetone for five minutes
to remove light oils. Air dry.
184.108.40.206 Soak parts in a commercial grade detergent and hot water
(120-160 degrees) for thirty minutes to remove heavy oils
and grease. Rinse clean with potable water until free of
220.127.116.11 Soak parts in a nitric acid pickle bath per ASTM-A-380,
Code D to remove heat scales and discolorations. Rinse
clean with potable water.
3.1 All components received will be inspected for damage during shipment
immediately after receipt of shipment.
3.2 All surfaces will be checked for visual damage to critical surfaces. If any
protective cover is separated from the component, the customer will be
page – 1 –
3.3 All quantities will be varied to the quantity shown on the packing list. If
discrepancies are found, the customer will be notified immediately.
4.0 STORAGE OF INCOMING COMPONENTS
4.1 All components will be stored in there shipping containers until preparation
4.2 All components will be stored with a work order detailing the quantity, EP
instructions and customer purchase order.
5.0 RECEIVING INSPECTION
5.1 An inspection will be undertaken prior to electropolishing to verify the
components conform to the specifications and/or the instructions so noted
on the customer P.O. or provided drawings.
5.2 If a specific surface roughness is specified by the specification and/or
instructions the surface may be checked with a profilometer as required to
verify that the initial surface is suitable for the instructed surface to be
6.1 The component will be polished as instructed on the work order.
6.2 The following steps define the electropolishing procedure.
6.2.1 The component(s) is to be racked in an appropriate manner to
assure secure anodic contact.
6.2.2 Place the component rack or fixture on the anodic bar over the
electrolyte bath and assure the component is fully submerged into
the electrolyte to cover the area which is to be electropolished.
6.2.3 Polish the component for the required time using the appropriate
18.104.22.168 Most electropolishing is performed using direct current
at 50 – 500 amp per square foot of polished area.
page – 2 –
22.214.171.124 Metal removal is controlled assuming 0.0001 – .00025
inches per surface per minute depending on the surface
finish before working and finish desired afterwards.
126.96.36.199 Using the above analysis the voltage is set beforehand
and the time of processing is determined by the surface
6.2.4 After examination of the first article(s), the time and voltage will
be recorded for the component(s) being electropolished.
6.2.5 The electrolyte used by CELCO is a proprietary fluid purchased
from Electropolish Systems, Inc. of Menomonee Falls, Wisconsin,
solution number 4000.
188.8.131.52 The electrolyte fluid specific gravity, 1.750 .020, is
extremely important to the process and must be balanced
within the suppliers tolerance. This balance must be
checked at least once a week. Another factor which can
cause erratic finishes is the iron content of the fluid. This
level should not exceed 3.5%. The indicator of high iron
content is usually a pitting of the finish on the flat surfaces.
If pitting of finish occurs, decant with new fluid to bring
solution back to appropriate iron level. If testing is essential
a sample of 200 ml should be sent to a laboratory for testing.
7.1 Following the electropolishing of the component the following rinsing
procedure is performed.
7.1.1 Rinse the components in the drag out rinse to reclaim EP fluid.
7.1.2 Clean water rinse.
7.1.3 Rinse in pigging fluid. This fluid is a 30% – 50% Nitric Acid Bath.
Fluid level will be controlled using equal strength fluid.
7.1.4 Rinse in first state water rinse.
7.1.5 Rinse in second state water rinse. The components can be stored in
this tank until final rinse.
page – 3 –
7.1.6 Final rinse is made with 8-10 MEG-OHM D.I. water.
8.1 The components are placed in a clean air flow area to dry.
8.2 The components are 100% visually inspected for consistency and
uniformity of electropolishing.
8.3 If required, the micro inch roughness is measured by a profilometer to
assure the required surface.
8.4 All rejects are either rerun or recorded for separate packaging.
9.1 Normal packaging of components are placed in plastic bags and heat
sealed to assure maximum cleanliness.
9.2 Large components which are not placed in plastic bags are wrapped in
appropriate material to assure maximum cleanliness.
9.3 The components are counted for final packaging and placed in the
original shipping container or appropriate container for final shipment.
10.1 All shipments are shipped by most efficient means.
page – 4 –