Problem with light manganese phosphate coating (parkerizing)

In summary: Any thoughts?In summary, the new Goff 1244 spinner hanger shotblast machine is doing a great job at removing any old coatings and oxidation, but when parts are Parkerized using the machine, they come out much lighter than when sand blasted. Chronital S20 Stainless Steel shot is being used instead of manual sandblasting, but the parts coming out of the shotblast machine still have a lighter coating than when sand blasted. Chrismay thinks that the new blasting regime is not producing as much exposed surface area, which is why the parts coming out of the shotblast machine only take a light coating.
  • #1
turbos4audi
10
0
Hello all,

We have a manganese phosphating process for gun parts and I am having trouble with some parts coming out with a lighter coating than normal. Our orginal steps which, for years, have produced repeatable high quality results are; Sand blast with aluminum oxide, phospahte bath at 190°F for 20-30 min, flowing water rinse, water displacing oil bath (WD-40), and then air dry.

What has changed is that we bought a Goff 1244 spinner hanger shot blast machine and are going to use it in place of the manual sandblasting. We are using Chronital S20 Stainless Steel shot. It does a great job at removing any old coatings and oxidation. But when we parkerize parts from this machine, they come out much lighter than when sand blasted.

I am going to set up an alkline bath and rinse to do between blasting and parking.

I want to see if anyone had any thought on this or experience.

Let me know if you have any questions.

Thanks,
Chris
 
Engineering news on Phys.org
  • #2
may i suggest a microscopic analysis of the surfaces under the old and new blasting regimes ? I'm thinking the new blasting is not producing as much exposed surface area.
 
  • #3
That is a great idea. We were just talking about the surface feeling smoother on the rifles coming out of the shotblast machine. I will find a microscope today.
 
  • #4
awol99 said:
may i suggest a microscopic analysis of the surfaces under the old and new blasting regimes ? I'm thinking the new blasting is not producing as much exposed surface area.

Hello,
So, 10x is the best magnification I could get right now. But even under that the shot blasted surface was much smoother than the sand blasted surface. I have a surface profile gauge on order to start getting some numbers to represent this.

We have removed all the Chronital S20 shot from the spinner hanger and replaced it with Grittal GM20 abrasive media. It is a stainless steel crushed media that is supposed to be comparable to the 50 grit Aluminum Oxide. The blasted surface is VERY similar to that of the aluminum oxide under 10X. But only with a hot water rinse before the phosphate bath we were able to get a dark gray coating. Without the rinse, ONLY the gas tube, takes a coating. It is mild steel ~30 Rockwell. ALL the hardened steel parts ~45 Rockwell (barrel, receiver, sights, gas block) take only a very light gray coating.

I have a load of GM30 Grittal coming tomorrow, slightly coarser.

Anyone have any thoughts on this?

The media is stainless steel, stainless does not parkerize. Could some of the media be leaving some sort of coating on the parts that is preventing them from taking a coating?

I am very stumped by this and very much need help.
 
  • #5


I would first suggest conducting a thorough review of your process and equipment to identify any potential sources of error or inconsistency. It could be that the new shot blasting machine is affecting the coating process in some way, such as altering the surface texture of the parts or introducing contaminants. Additionally, the use of stainless steel shot may be causing a different chemical reaction during the phosphate bath.

I would also recommend testing different variables, such as the temperature and duration of the phosphate bath, to see if those have an impact on the coating results. It may also be helpful to compare the results from the new shot blasting machine to the previous manual sandblasting method to determine if there are any noticeable differences in the coating.

Another potential solution could be to consult with experts in the field of manganese phosphate coating and get their insights and advice on the issue. They may have encountered similar problems and can offer potential solutions or suggestions.

Overall, it is important to approach this problem systematically and gather as much information as possible in order to identify the root cause and find a solution. Good luck with your investigation.
 

1. What is light manganese phosphate coating (parkerizing)?

Light manganese phosphate coating, also known as parkerizing, is a chemical process used to create a protective layer on metal surfaces. It involves immersing the metal in a solution of phosphoric acid and manganese phosphate, which creates a porous layer of iron and manganese phosphates on the surface of the metal. This coating provides corrosion resistance and improves the adhesion of paints and other coatings.

2. Why is there a problem with light manganese phosphate coating (parkerizing)?

The problem with light manganese phosphate coating (parkerizing) is that it can sometimes result in an uneven or blotchy appearance on the metal surface. This can be caused by various factors, such as improper surface preparation, inadequate coating solution or temperature control, or contamination of the coating solution.

3. How can I prevent the problem with light manganese phosphate coating (parkerizing)?

To prevent the problem with light manganese phosphate coating (parkerizing), it is important to follow the proper procedures and guidelines for surface preparation, coating solution preparation and temperature control, and contamination prevention. It is also important to use high-quality materials and equipment and to regularly monitor and maintain the coating process.

4. Can the problem with light manganese phosphate coating (parkerizing) be fixed?

Yes, the problem with light manganese phosphate coating (parkerizing) can be fixed. The first step is to identify the cause of the issue and address it accordingly. This may involve re-doing the coating process with proper procedures and materials, or using special techniques to remove the uneven coating and reapplying it. It is important to consult with a professional or refer to specific guidelines for the best approach to fixing the issue.

5. Are there any alternatives to light manganese phosphate coating (parkerizing)?

Yes, there are other types of coatings that can provide similar benefits to light manganese phosphate coating (parkerizing). Some common alternatives include zinc phosphate coating, zinc-nickel alloy coating, and black oxide coating. Each of these coatings has its own unique properties and application methods, so it is important to research and determine which one is best suited for your specific needs.

Hot Threads

Recent Insights

Back
Top