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Polishing aluminum with a blast cabinet

2005

I need to find a way to blast (polish) cylinder heads to make them look as though they have been polished or at least as good as new. The part in question is a Kawasaki KZ-900. It is a cast aluminum part.

When blasting with a 400 or 600 grit glass bead it leaves a flat dull finish. Is there anything that will give a more glossy finish. What should this be sealed with?

NOTE: When some of the heads are stock from Kawasaki they appear to semi-polished with a high-temp clear coat of ?

Thanks

Jeff Eurich
restorer - Holland, Michigan

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2005

Hello Jeff,

I have a similar problem, except that I am working on cast aluminum engine parts from 1960s Mercedes cars. From experience and talking with glass bead vendors, I have learned a couple of things.

First, use the smallest beads you can get. I don't know what the size of a 600 grit bead is, but I am using a bead that is .0015" that I believe is referred to as an "AQ" size. I understand that I can special order an "AS" size that is even smaller, but have not done so yet.

Second, glance the beads off the part at about 45 degrees.

Third, do not exceed 40 psi at the gun. 35 psi is even better. This low pressure is to insure that the bead hits the part and bounces off, rather than shattering. The problem is that most "hobbyist" blasting guns flow so few beads at these pressures that it takes forever to get any results.

I cannot get my blaster to flow well at these pressures and therefore have to run the pressure up. The results are not bad, but not the near-mirror finish I need.

Last summer I heard about, and tried, ball burnishing. This is actually similar to bead blasting except it is done with steel balls and sharp steel pins and is performed in a large vibratory tub. I gave the company a really nasty looking valve cover to do as a sample. The burnished unit came back looking pretty good on the outside, but on the inside where it had not been so badly oxidized, it looked simply fantastic.

What I am going to try next is to bead blast the unit myself with the smallest glass beads to remove any oxidation and clean the part, and then have it ball burnished. I expect that this will gave me the same terrific finish all over the part. The other choice is to buy a much more expensive blasting outfit.

The ball burnished surface still needs to be protected for long term appearance reasons, and I am not sure what will accomplish this. I am going to try clear anodizing though.
Any thoughts?

Chris Johnson
- Boulder Creek, California, USA

There are several body shops using baking soda as a blasting medium, although I have yet to try it myself it is said to actually polish both glass and trim on a car that is being stripped. This may be appropriate to your situation. I would suggest talking to some local shops that have first hand experience with soda blasting.

Wayne Paul
- Saskatoon, SK, Canada
2005

An excellent media is plastic pellets, blasted at low pressure. Media cleans without etching, is excellent for reclaiming and comes in different hardnesses.

Mavoric J. Farmer
Miric and Associates, LLC - Rockford, Michigan
2005

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I have restored hundreds of motorcycle castings using a combination of techniques. First degrease, second blast using a wet blaster at 40psi loaded with 100/150 media.
The final trick is to reduce the contour lean average in a mass vibrator. The effect is better than new. The equipment is expensive and not suited to small businesses

Stephen Smethurst
- Manchester, England
2005

I think the medium you might be looking for for a "close" to polished finish is walnut shell media ⇦this on eBay or Amazon [affil links] . But, even after getting the aluminum smoothed-out after blasting I continued the polishing with buffing wheels and jeweler's rouge ⇦this on eBay or Amazon [affil links] . All the engine covers and other parts of my Yamaha that are bright aluminum alloy are now mirror finished with an amazing effect that looks better than chrome.

Rick Massey
bikes - Billerica, Massachusetts
2006

Soda blasting will return your part to like new condition.except it will not remove heavy oxidation. there is no need to degrease before you blast and it will not harm your delicate components.it will not remove any base material and soda is a corrosion inhibitor . you do need to clean with water before coating

Andrew Defoe
- Cattaraugus, New York
June 24, 2008

If you want to get a "polished" look through a blast finishing process on cast aluminum you might want to try using cut wire zinc shot as a media. The size is not really important, but most home/shop systems will not handle anything larger than .023 diameter. You will want to play with pressures from 45 to 85 psi in a suction blast system. Due to the softness of the zinc cut wire it is not highly abrasive. The supplier I have used in the past is Pellets, LLC in New York.

Guy Smith
- Kings Mountain, North Carolina
June 25, 2010

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Q. We are cleaning some bronze castings and the insides need to be smooth and polished. These are sand castings and the texture needs to be removed. Is there a blast media that will do this?

DOUG FERGUSON
- SANTA ANA, California, USA
December 7, 2012