Removing Mill Scale from Raw Steel

Our steel supplier has a plate blaster. You coould buy your stock pre blasted or buy a beam blaster.

Dear Randouli,

Can you please provide more information about the product "Plate Blaster" with some photos.

Here you are Abdel Halim Galala:

http://www.oceanmachinery.com/pangborn_blastcleaner.htm

http://www.tumbleblast.com/pangbornstructuralblaster.htm

Milo

In past there was 7 tank cleaning process where steel components were cleaned with diluted HCL and Trichloroethane. Now I understand that there are some liquid chemicals available which have eliminated this 7 tank process. Also there are some Herbal chemicals soluble in water are available which are applied before final painting instead of primer painting. Such Herbal chemicals are sold @ $3/ liter.

One of the ways that we cleaned the scale off, was to run the beams through a shot blast machine. This one was built by Wheelabrator, but Pangborn also makes these systems. Check for used ones, probally could get a good deal given the times.

We looked at shot blast in house - not cost effective nor do we have space available. Our structural steel (H & W beams, channel, angle) we occasionally order pre-blasted.

What I'm looking for is a way to remove only the scale which was disturbed during the weld process - approx 3" wide by the length of the beam and this is not consistent. I've considered a bolt on device for the SAW welder itself but again, air quality is an issue as well as confined area for particulate collection.

Currently, I have updated the SOP's to include manually scraping the scale off during the additional welding. I'm hearing a lot of grumbling as a result.

Just looking for options.

Did I mention additional capital is not an option?

Re: "We looked at shot blast in house - not cost effective nor do we have space available.... we occasionally order pre-blasted. I'm looking for a way to remove only the scale which was disturbed during the weld process - approx 3" wide by the length of the beam and this is not consistent.... air quality is an issue.... manually scraping (is causing) a lot of grumbling... Did I mention additional capital is not an option?"

Sounds like you're seeking the proverbial "Silver Bullet". We've LONG known how serious the problem of mill scale CAN be, depending on the environment to which the final product is subjected [e.g., the "Liberty Ships" sinking at pierside due to hull perforation, while STILL be outfitted!]

Your steel buildings: they are going to be erected inside of climate controlled caverns? Or (more likely), subjected to blistering sun, humidity, ice, wind, rain, etc?

I am curious as to what the Specification is (from the coating manufacturer) regarding mill scale. Do they tell you: "Simply hand wire brush over the scale, and slap our product on"...? (if so, you must be using the product that actually calls itself "Silver Bullet")

I've seen galvanizers use acid baths to remove mill scale before hot-dipping... and pipe coaters using the wheelabrator shot-blasters to prepare for FBE application (fusion bonded epoxy).

YOU seem to be the only one in your company who understands the importance of removing the mill scale {you probably have the benefit of either SSPC or NACE education?}.

If there's no Blasting Yard in your vicinity, to run stuff through before coming to you for coating, then a dedicated in-house station for needle-scaling / power wire brushing is probably your only viable option (to insure a quality job).

But, I'm ready to 'subscribe' and listen for any state-of-the-art ideas... anyone using thermal-microwave-UV-laser-induction mill scale removal techniques...?

Yeah I guess I am but there must be a simple solution that I'm just not seeing.

Maybe not - thought I'd throw it out there for some feedback - Thanks for yours - much appreciated!

Thanks for others comments as well.

Hello,

I work for a manufacturing company and we use a 7 part cleaning system before our parts hit the paint line. It is phosphate based and works great on the laser scale.

Angie

Mentor, Ohio

No room for cleaning tanks - did I mention these components can be up to 50' in length?

Thank you!

Hi Again Camilliontwo1.

milo here.

Try this:

http://www.shorechemical.com/Section%207%20Tech%20Sheets/naval_jelly.htm

Active ingredient is phosphoric acid.

milo

http://www.norfolkiron.com/page.asp?pageID=17 You can receive your steel blasted and then touch up by hand. This can be done with grinders, or air blast systems like sand blasting or shot blasting in a blast room. Look at the ROI and you will find your solution.

High Pressure Water jet cleaning can do the trick. In fact, a portable system from KARCHER can even clean, de-rust, & give a 3 to 4 mue Zinc phosphate coating. This will be a good & simple pre- treatment step, before painting on fabricated panels & plate. For more info. please visit www. karcher.com & choose the best suited model for your application. Good Luck ! Rangasamy

Without layout, sizes of products, etc., we can only imagine the real operating conditions prevalent in your shop.

Why don't you sequester your shop's informal leaders, leadmen, supervisors and engineers for an hour of brainstorming?

With all due respect, I don't think they'll still grumble if they are made to see the financial effect of poor quality production. Show them the quality statistics, and how this is harming the bottom line. Then, allow them to brainstorm. it's their shop, they should know how to deal with the problem.

Off the cuff, I'm imagining a jig outfitted with a pair of pneumatic rotary brush grinders where the shapes will move through, pushed by hand on a roller table. But like I said, I can only imagine.

When it comes to shot blast equipment larger automated blasters become a reality when companies understand the reduction of labor costs. Hand cleaning beams is time consuming and usually ineffective. A shot blasted surface, depending on white or near-white metal, is free of rust, scale and other contaminants. This provides a better value for your customer and long term ease of maintenance with fewer corrosion related failures. When the steel is cleaned prior to fabrication it also reduces wear on cutting tools including bandsaws and drill bits lowering production costs.

Thanks to all!

Under evaluation - Great comments.

CAM

LS Industries manufactures a series of airless shot blast systems to clean and prep steel plate and structural shapes. LS Industries can be reached at 800-835-0218. Ask for Michael W.

Dear Sir

We need mill scale and we prefer the good quality rather than the good price.

Is it possible for you to supply us the mill scale?

We are a Japanese company and have an office in Tianjin, China.

I am yogi from Tianjin office.

Removed email address

- CR4 Admin

Say what??

What do you need mill scale for??