Barrel Electropolishing

We recently had a customer ask us: “Do you do barrel electropolishing, or do the products have to be racked?”

To the best of my knowledge there is no way to do barrel electropolishing. All products need to be racked. The reason for racking the products to be electropolished is because they need to be individually connected to the electrode to receive the electric charge for the process to occur.

Passivation and Pickling

It is however possible to do barrel stainless steel passivation or barrel metal pickling. There are many passivation manufacturers which have a barrel and some sort of shaking process which makes sure that the products get full coverage across the surface of the product in the liquid.

The main reason that electropolishing is a costlier process than passivation or pickling is because the products need to be individually racked for electropolishing and this costs more in labor time.

 

A Banner Year

We realized that it has been a while since we have posted. Time flies when you are really busy. We wanted to thank all of our wonderful customers for continuing to help us grow and spread the word about our organization. Its looking like 2015 will be our biggest year to date. Thanks!

Passivate Per ASTM A967

astm a967

We see a lot of medical device drawings mentioning passivated per ASTM A967. We have done hundreds of projects which include this standard specification. We understand how precise and repeatable stainless steel medical device products need to be. Per the ASTM website ASTM A967 relates to:

This specification covers several different types of chemical passivation treatments for stainless steel parts. It includes recommendations and precautions for descaling, cleaning, and passivation of stainless steel parts.

Passivation and Electropolishing

Along with electropolishing we do a lot of passivation projects here. Passivation is a simpler process than electropolishing and often more affordable. Passivation can be done in batches whereas electropolishing needs to be done with each part being independent. If you are a device designer or researcher and need help passivating your products to the ASTM A967 specification don’t hesitate to reach out today.

Electropolishing FAQs

We get so many questions here that we like to write some of them down in the event you have a similar question:

Do you usually electro polish on the entire part including the tip?

Yes! Usually we electro polish the entire work piece. There can be a small mark where the work piece is being held but otherwise we do electropolish the whole part.

Can you do a different finish to the tip vs. the shaft?

Yes! You can electropolish only the tip if you would like. Electropolishing is basically dipping the product in electrolyte and sending current into the piece. You can control how much of the product is dipped into the solution and that is the part which get’s electropolished. It is difficult to hold extreme tolerances when electropolishing just a portion of the work piece but it is possible.

Since electro-polishing sheds a layer – is it problematic with thin parts in the design? is the shedding uniform or relative to original dimensions?

Electropolishing is uniform across the area exposed to the Electropolishing. The amount of material lost can be controlled to a high level of precision On a nano level, electropolishing does remove peaks faster than valleys, which makes it smoother, but this doesn’t affect the relative design on most products.

Electropolishing Process

Depending on the industry standard you are working with, your electropolishing process can differ in a few ways. Make sure to consult with the ASTM standards for your industry or regulatory group. Below we will identify a typical electropolishing process including the pre-electropolishing and post-electropolishing methods for the perfect surface finish.

Pre-Electropolishing

It is important that all surfaces be uniformly exposed to the electrolyte solution so a pre-electropolishing wash process should be established. Classic Electropolishing puts all parts through a wash and rinse cycle with agitation to get any surface imperfections such as coolant or grease off of the parts. 

Carefully inspect your welds to ensure that the part has continuous seams and is free of pits or gaps where the electrolyte solution could collect.

Electropolishing

The electropolishing steps are discussed in additional posts on this blog. Recently we discussed the steps of DIY Electropolishing. DIY Electropolishing.

The basic steps of electropolishing include: heating the electrolytic solution, securing your work piece to the electropolishing tooling, submerging your work piece into the electrolytic solution, turning on the proper amps of electricity to begin the actual electropolishing.

  1. Heat the electrolytic solution securing your work piece to the electropolishing tooling, submerging your work piece into the electrolytic solution, turning on the proper amps of electricity to begin the actual electropolishing.
  2. Secure your work piece to the electropolishing tooling submerging your work piece into the electrolytic solution, turning on the proper amps of electricity to begin the actual electropolishing.
  3. Submerging your work piece into the electrolytic solution turning on the proper amps of electricity to begin the actual electropolishing.
  4. Turning on the proper amps of electricity to begin the actual electropolishing
  5. Set your timer to when the workpiece will be done electropolishing.
  6. Pull your workpiece out of the electrolyte solution and begin the post electropolishing process
  7. Neutralize your parts
  8. Rinse

Depending on the design specifications of your electropolishing process, you may need to electropolish the product, re-rack the product and then electropolish again so as to make sure that the entire workpiece is electropolished otherwise you might get extensive marks where the workpiece was being held in the rack tooling.

Post-Electropolishing

Following electropolishing all traces of the electrolyte solution are to be thoroughly removed from the part. One process to use after the part has been electropolished is a nitric acid followed by a hot rinse, followed by a rinse, followed by drying. According to ASTM B912 the electropolisher must include post-coating procedures as part of the process, as well as performance testing by means such as a salt spray test, a humidity test or a copper sulfate test. Surfaces should be dried with a soft, non-particulating cloth.

The preceding was meant to serve as an introductory blog post describing the steps of a typical electropolishing process. We have seen many different types of electropolishing processes. If you have variant processes or process improvements we would love to hear about them.

Metal Surface Imperfections

Top engineers demand perfect surface finishes. What do they do when part of the machining process causes metal surface imperfections? One option that helps in a variety of situations is electropolishing.

Common Imperfections

Metal surface imperfections can happen in manufacturing for a variety of reasons. Most often imperfections happen as a result of an abrasive machining process. During the abrasive process a machining tool comes into contact with metal to remove materials and some of the material is left behind.

Burr —a metal imperfection characterized as a thin ridge of roughness left by cutting operations such as shearing, slitting, trimming, blanking, etc

Chatter—(metal) a series of traverse marks in the metal.

Dent—a mark transferred to a substrate surface from an imperfect process roll or something on a roll. The most common causes are tape, metal particles and dirt.

Metal marking—black or gray marks left on a painted strip when bare metal is drawn across its surface. White and light-colored coatings are more susceptible to metal marking than dark coatings. Metal marking typically occurs during forming operations.

Orange peel—a paint imperfection where the surface resembles the skin of an orange; also surface roughening on formed products resulting from the use of coarse-grained material.

Red rust elimination —residue from the corrosion of steel consisting of iron (ferric) oxide. The oxide is reddish in appearance (rust colored). Red rust may also manifest itself on galvanized steel. In this case, the protective zinc coating has been completely corroded exposing the underlying steel. Caused by the exposure of steel or iron to moisture.

Detection of Imperfections

As referenced by the variety of imperfections above, incorrect parts happen for many reasons. Many imperfection can be discovered with proper quality checking procedures. These types of procedures can be as advanced as looking through complex microscopes and can be as simple as spotting imperfections with plain eyesight. What is most important is that you have a system in place to catch imperfections and you know how to remedy them to a more perfect part.

How Does Electropolishing Cure Imperfections?

Electropolishing is a subtractive process which removes material from the service of your workpiece to create a smoother surface. Small burrs and imperfections are removed during the electropolishing process. Larger burrs produced in rough milling or displaced metal from drilling operations often need pretreatment using other methods. 

DIY Electropolishing

We wanted to provide a simple informational post for electropolishing hobbyists who are interested in DIY Electropolishing. Please bare in mind that there are potentially environmental and health ramifications of electropolishing chemicals which you must consider. Please consult EPA literature on chemical usage and disposal before attempting to electro polish. Also if you plan to electro polish a product for market, make sure that you are adhering to ASTM standards for the industry you are in.

There are three main pieces of the puzzle you will need for your DIY electropolishing project: 1. Electrolyte formula 2. Container 3. Electricity

Electrolyte Formula

I personally started out using commercial formulas such as the one made by ESMA. Other DIY electropolishers like to make the formula themselves. Here are a couple of recipes I found on

The Metals Handbook, Vol 2,”Heat Treating, Cleaning and Finishing”, 8th
edition gives a couple of recipes:

#1 sulphuric acid 41%
phosphoric acid 45%
water 14%
operating temp: 170-230F
current density: 200-350 A/sq.ft.

#2 phosphoric acid 56%
chromic acid 12 %
water 32%
operating temp: 80-175F
current density 100-1000 A/sq.ft.

All percentages by weight. You might want to get a copy of the book. It
contains articles on electropolishing and every other finishing method you
could want. Copies are available on the used book sites.

Electropolishing Tank or Container

Use a stainless steel container as the cathode (negative electrode) double welded inside and out. Stainless steel can withstand high temperatures, which are needed if too much water enters the electrolyte. The container should be larger than the part you plan to electropolish. Most industrial containers used in electropolishing also have a heating system for the electrolytes. The correct temperature for the electrolyte formula is between 150 and 220F. 

Electricity

The electricity is connected to the part you plan to electropolish. For electricity you can use something as simple as a 12 volt battery. The amount of amps that you send to the work piece depends on the surface area of the work piece. Here is a link to a decent formula you can go off of. http://www.surfinetek.com/electropolishing/electropolishing.html

The commercial version of your electricity source looks more like this –

DIY Electropolishing

DIY Electropolishing

Connecting the Electricity

The “current connection” in the above picture is what you would connect to your part and then submerge in the electrolyte formula. Once you have gotten your DIY electropolishing system down, you can get a commercial rack system like this to crank out thousands of stainless  steel products at a time  – http://www.associatedrack.com/products_electro-polishing-tooling.html

Here are a few additional discussions on the topic:

  • http://www.practicalmachinist.com/vb/general/small-scale-electropolishing-diy-techniques-150006/
  • http://bbs.homeshopmachinist.net/archive/index.php/t-38026.html

We hope that this post on DIY electropolishing was helpful. This blog post was meant to be informational and provide a general roadmap to understanding electropolishing. Please consult additional resources or an expert before electropolishing. We take no responsibility for adverse outcomes resulting from DIY electropolishing attempts. Once you have mastered DIY electropolishing, you can also develop a process for pre and post cleaning of your work piece which all industrial electropolishers have.

If you are looking to take your project from the garage to the industrial don’t hesitate to reach out. We offer top of the line electropolishing services!

 

Another Reason to Electropolish Your Food Equipment

In the past we have detailed some of the reasons for quality minded food industry companies to  electropolish equipment, here is one more reason. A recent report from UltraClean Electropolish Inc in Food Engineering Magazine points to the fact that electropolishing can reduce the time it takes to clean your equipment.

For one, electropolishing creates a smoother surface which means there is less space for food to get caught in hard to reach areas. In the report, due to the typical cleaning time saved, the company was able to recover the costs of electropolishing on their food industry equipment in less than 90 days. Not only does electropolishing lead to less cleaning time, it leads to less possible food contamination since there is less space for food to be left behind.

Let Classic Electropolishing help out with your next food equipment project.

Used Electropolishing Equipment

Classic Electropolishing enjoys seeing all types of high quality electropolishing equipment. Are you looking for equipment or do you have equipment that you are looking to get rid of, contact us today and we will see if we can help. In the past we have dealt with used electropolishing equipment from ESMA as well as custom made used electropolishing equipment. If you need help setting up equipment or if you have equipment that you are auctioning off or liquidating, contact us today.

Classic Electropolishing does our own in-house electropolishing and we also coach companies on how they can set up their own in-house electropolishing process.

 

Electropolishing Threads

Here are a few more electropolished goods directly off the rack. Electropolishing threads can cause difficulties if there are tight tolerances on the minor diameter and pitch of the thread. If you have tight tolerance threads, make sure you are working with an expert electropolisher. At Classic Electropolishing we understand how valuable the machining process is prior to electropolishing. We can keep material removal tolerance to +/- .0001.

Electropolishing Threads

Electropolishing Threads