PSFC Electropolishing Stainless Steel


Plasma Science and Fusion Center

Office of Environment, Safety, and Health


190 Albany Street, NW21 2nd floor
617-253-8440 (Catherine Fiore)
617-253-8917 (Matt Fulton)
617-253-5982 (Bill Byford)
617-258-5473 (Nancy Masley)
                                                 Fax 617-252-1808

Be Safe or Die


Reviewed and Approved By:

T. Toland
A. Kalil

Catherine L. Fiore, PSFC Safety Officer


Standard Operating Procedures for Electropolishing Stainless Steel

 

Authors:  C. Fiore/R. Childs

 

Version:  1.3

 

Date:  August 14, 1992,   Revised  June 01, 2007

 

Persons Responsible:   R. Rosati

                                  T. Toland                    


 

Introduction:

 

This document outlines the hazards involved with electropolishing operations at the PFC.  It details procedures to be followed to minimize the risk of exposure of Plasma Science and Fusion Center employees during electropolishing operations.  These procedures are appropriate for the handling and use of most electropolishing materials.

 

Scope:

 

This procedure covers employee safety during the handling and use of electropolishing chemicals during electropolishing operations.  These procedures involve the mixing and use of a 1800 ml mixture of sulfuric acid, phosphoric acid and glycerin.

 

Safety Analysis:

 

Failure to follow this procedure could result in severe skin and eye irritation or burns, from direct contact with acids and alkalies.  Acid vapors are irritating and may be corrosive to the respiratory system.  Electropolishing evolves small amounts of hydrogen gas which can react explosively in the presence of an ignition source.

 

Definitions:

 

Primary Irritant - Capable of causing tissue damage and burns resulting from direct contact.

Responsibilities:

 

The supervisor or responsible person shall designate employees who are required to work with acids in order to do electropolishing, and train them regarding the health and physical hazards and appropriate work procedures. The supervisor or responsible person shall ensure that necessary personal protective equipment and spill control supplies are available to employees.  The supervisor or responsible person shall ensure that operations utilizing acids and alkalies are performed in accordance with good work practices in adequately ventilated areas.

 

Assumptions:

 

Employees shall be familiar with the hazards associated with acids and appropriate spill and emergency procedures described in this document.  The users shall be trained in the use of appropriate personal protective equipment.  If respiratory protection is to be used, such protection shall have been obtained through the Industrial Hygiene Program and employees shall have received fit tests and appropriate medical examinations.

           

Required Supplies:

 

      Protective gloves.  Gloves shall be worn whenever acid and alkali solutions are handled.  Heavy Nitrile, Neoprene, butyl rubber, 4H, or other impervious gloves shall be worn whenever concentrated solutions are dispensed.  Discard gloves if any holes or leaks develop.

 

      Eye and Face Protection.  Face shields are required when mixing the solutions and during electropolishing.   Eye protection should be worn underneath the face shield.

 

      Protective Clothing.  A lab coat and an impervious apron shall be worn while mixing the solution and while performing the electropolishing. 

 

      Spill Materials.  Neutralizing, absorbent materials should be obtained to control spills.  Appropriate spill control materials may be obtained from VWR.  An appropriate container for holding any spill clean-up materials is also required.

 

General Procedures:

 

1.   Read MSDS on Phosphoric Acid, Sulfuric Acid and Glycerin.

 

2.   Room NW21-167 has a chemical hood and an enclosure dedicated to electropolishing small parts. All procedures related to this SOP must be performed under ventilationm . The chemical hood must be used when pouring concentrated acids.All work must be done under a hood. Room NW21-167 has a hood dedicated to electropolishing small parts.

 

3.   A lab coat, impervious vinyl apron, nitrile gloves, and a face shield must be worn. Assemble spill materials prior to beginning work.

 

4.   If it is necessary to prepare the electropolishing solution then proceed with the following steps. If it is already set up, skip to step 8.

 

5.   Insert the cylindrical copper electrode into the 2000 ml beaker so that it presses tightly against the inside of the beaker. The tab that hangs  over the edge of the beaker is where the anode (negative) clip lead from the power supply connects. The tab should bend down and back up. This is to prevent any of the solution that might run over the edge from collecting on the clip, causing it to corrode.

 

6.   In a 2000 ml Pyrex beaker mix the following solution using a Pyrex or polyethylene graduated cylinder: 900 ml Phosphoric Acid, 720 ml Sulfuric Acid, and 180 ml Glycerin. This is in a 5:4:1 ratio. Be sure to rinse the graduated cylinder in the sink with copious amounts of tap water and thoroughly dry it after each chemical is added.

 

7.    The beaker with anode and solution is now placed in a larger beaker jar with a boiling screen between them. Enough water is then added to the large beaker jar to come up about half way in the beaker jar. This creates a double boiler that is then set on a hot plate. The hot plate is set on a ring stand base so that a safety ring can hold the assembly securely in place on the hot plate and provide a post for holding the cathode clip lead with ring stand clamps.  Label the beaker as H3PO4/H7SO4 and "Corrosive".

 

8.    With the electropolishing solution in place, insert a thermometer into the solution and turn on the hot plate to medium-low to slowly warm the solution to 80C. DO NOT allow the water in the outer beaker jar to come to a boil, as this would heat up the solution too fast and would cause you to overshoot the 80C. If the solution were to get too hot and boil the splashing would be very dangerous. From this point on the whole operation must be under constant observation to prevent any runaways. If you must leave for even a short time the hot plate must be turned off, the power supply turned off, and the parts removed. NO EXCEPTIONS ARE ALLOWED!

 

9.    In addition to the solution there are two other hot plates with beakers that need to be filled with distilled water and brought to a boil.  In this case you can set the hot plate to high heat to get the water up to a boil and then turn it back. These two beakers are for a double rinse of the parts as they come out of the solution. You should allow the parts to sit in each rinse for a few minutes to insure a good rinse.

 

10.  While the different baths are warming up, the parts can be prepared for the solution by making hangers from bare copper wire to suspend the parts in the solution. Use the cathode (positive) clip lead to hold the end of the hanger wire just out of the solution by the clip. The clip is held in position over the solution by a ring stand clamp. The part should be completely submerged in the solution with the clip at least two inches above the solution to prevent it from corroding.

 

11.  Turn the voltage and current pots down to "0" on the power supply and turn on the power supply. Set the voltage to 6 to 9 VDC and slowly turn up the current to give a rate of 3 1/8 Amps per square inch of surface.  Do not exceed 12 Amps for this size beaker. For small parts like screws keep the current down to 1 or 2 Amps to prevent high current density erosion of the tips of threads and other sharp edges that you may not want removed. Small parts like screws should be checked more frequently than larger parts for this same reason. Whenever the PARTS are REMOVED from the solution the POWER SUPPLY should be turned OFF FIRST to prevent any arcing to the solution.  The electropolishing process generates hydrogen gas and an arc could produce a small popping like explosion above the solution.

 

12.  When you are satisfied that the parts are done they should be put in the two rinses as described in step 9. When they come out of the rinse lay them on a clean paper towel to dry and cool. A thorough washing in an alkaline detergent and water should be done to insure all the electropolishing residues are removed and neutralized.

 

13.  The last step is to turn off all the hot plates.  The power supply should have been turned off in step 11.

 

       When the rinses have cooled they can be dumped down the drain with cold water running to insure good dilution. Leave the cold water running for a minute or two to make sure. Wash the beakers with the glassware cleaning detergent and put them on the drying rack.

 

       The electropolishing solution should be left in the beaker setup to cool and can be used many times before it is spent. Finally it goes with out saying that any drips or tiny spills should be wiped up with a soapy sponge to neutralize the residue and therefore prevent corrosion of the equipment.

 

14.  If you have parts that must be electropolished on the inside, see Bob Childs for special instructions on internal anoding.

 

15.  A copy of this SOP shall be posted in NW21-167 near the electropolishing hood.

 

Training:

The supervisor or responsible person shall supply this procedure to affected employees and verify that they understand it.  Employees should understand the health and physical hazards of acids and alkalies.  Incompatibility of oxidizing acids or caustics with organic solvent should be emphasized.   All users must complete  MIT's General Chemical Hygiene Training,  Managing Hazardous Waste Training,   PSFC Lab Specific Chemical Hygiene Training and must sign a form acknowledging that they have read and understood the  PSFC Chemical Hygiene Plan.

 

Spill Procedures:

1.    Refer to the product Material Safety Data Sheet for proper spill clean-up procedures. 

 

2.    Do not attempt to clean up any large spills, especially if the vapors from the spill result in noticeable eye or respiratory irritation.  For large spills, shut off any ignition sources, and call the EHS Office at 2-3477 on weekdays between 9 a.m. and 5 p.m.  At other times call x3-1500 (Control Center).  If there is personal injury or a strong threat of personal injury, dial 100.  Do not let anyone enter the spill area.  Small spills may be cleaned up by the person who caused the spill. 

 

3.    Do not attempt to clean up any spills without wearing gloves, eye, and face protection.  Acids may contaminate footwear during clean-up of a spill.  If there is any possibility of contamination of footwear while cleaning up the spill, obtain shoe coverings or rubber boots. 

 

4.    Control the spill with an appropriate neutralizing agent such as soda ash (sodium carbonate) or lime (calcium oxide).  Apply the agent from        the outside perimeter of the spill toward the center to avoid spreading the material.  Scoop the material into a suitable container.  The                container should be dedicated to the neutralized materials.  Do not place other solids (gloves, sponges, etc.) in the same container.

 

5.   Carefully rinse contaminated areas with water.  Sponges used to absorb the rinse water should be added to the spill clean-up wastes.  Put gloves, sponges, etc., in a separate solid waste container.  Avoid using paper towels on acid spills if at all possible.  Paper towels may only be used to wipe up dilute acids since strong acids may cause oxidation and heating of organic materials such as paper.

 

6.    Label the waste container and contact the EHS office  (2-3477) for pick up of the spill clean-up materials or contact the Chemical Hygiened Officer for transfer to <90 day waste storage.

 

First Aid Procedures:

1.    Any splash or exposure of the skin should be immediately, thoroughly flushed for 15 minutes.  Do not allow contaminated clothing to remain in contact with the skin.  If skin irritation or dermatitis develops, the affected individual shall be examined at the MIT Medical Department and referred to EHS for follow-up. 

 

2.    In the event of eye contact, 15 minutes of flushing with water is required.  Dial 100 for emergencies.

 

3.    If an individual has lost consciousness, dial 100 for emergency assistance.

 

4.    In the unlikely event that an individual ingests acids or alkalies, immediately call the Medical Department or dial 100 for emergency assistance. 

 

Waste Disposal Procedures:

 

Electropolishing solutions may not be put down the drain, whether or not they have been neutralized.  Any questions on this subject may be directed to the EHS Office (2-3477)

 

Place electropolishing waste solutions into clearly labeled, appropriate containers designated for this purpose.  Do not mix different kinds of acids together unless instructed to do so by the supervisor.  Red hazardous waste labels are available from the Chemical Hygiene Officer and from EHS. Store partially filled containers in an appropriately labeled satelite accumulation area.  When the waste container is sufficiently full or when the experiment using the acid solution is complete, contact EHS (2-3477) for pick up or the Chemical Hygiene Officer for transfer to <90 day waste storage.

This page maintained by Catherine L. Fiore FIORE@PSFC.MIT.EDU