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topic 3591

Proper plastic material to build a tank for surface etch of stainless steel


(1999)

To whom it may concern:

I need a welded plastic tank,1/2" wall thickness to electroetch or electrodeposit that will withstand solutions of Ferric Chloride & Hydrochloric acid electrolytic solutions. Citric acid may also be used in the formula. This is for the finishing surface treatment of various grades of stainless steel plating to 18" x 24" in size. the biggest problem I'm facing is that every plastic fabricator that I give my plans to, each wants to make the tanks of a different plastic sheet and only bond the seams with a liquid weld, which will not last. I need an honest answer as to the best material to use for the electrolytes that will be used for surface treating my stainless steel plates! If, anyone can be of help it would be greatly appreciated.

Sincerely Yours,

Richard B [last name deleted for privacy by Editor], Ph.D
- Clovis, California


Plastics and Composites Welding Handbook

(1999)

In life there is rarely an ideal answer, always a balancing of this against that; that's probably what's happening here.

The majority of plating tanks today are made of stress-relieved polypropylene, and I think that will probably be fine for your applications, assuming the temperature is not more than about 175 degrees F. The biggest disadvantage of polypropylene is that it is flammable; an electrical short or an unprotected electric heater can ignite it.

Polypropylene tanks can be put together by hot-air welding or by fusion welding; neither is unsatisfactory.

A less expensive but perhaps acceptable alternative would be molded polyethylene tanks, which are available only in select sizes. Polyethylene is chemically very similar to polypropylene but is not quite as rigid and the temperature limitation is about 140 degrees F.

The only other plastic material in the running would be vinylester fiberglass. I have successfully used hundreds of such tanks.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


Plastic Welding Kit

(1999)

Since you have not mentioned a temperature, PVC will work for room temp to about 110F, is cheaper and welds easily.

My preference in tanks the size that you mention is either polyethylene or polypropylene rotationally molded tanks. No seams and significantly cheaper. Can easily be reinforced with painted 2x4 and or plywood. The inside surface is somewhat rougher than a welded tank, but for your use, it should not ba any problem.

The best supplier that I have found for small quantities is U.S. Plastics in Lima, OH. Excellent service and price. For large quantities, consider Chemtainer. They are in several states and home office is in NY.

James Watts
- Navarre, Florida


(1999)

Hi Richard,

All the comments above are applicable!

To save $ use a moulded Poly tank ... rect. ones are available in Canada & the USA up to 500 gallons. It would save you a fortune. Max. temp. is l50° F and largish/longish Pe tanks need a brace (wood or metal) as they'll tend to bulge out on the sides particularly if they get hottish. Also consider using either PVC or PP tank adaptors. Less expensive than making and welding on Pe outlets.

Although Pe like PP will burn, it's a very slow burn. ABS will really take off ... and the now (thank heavens!)forbidden super plastic of cellulose nitrate would/could put cordite to shame! PVC doesn't burn (till you hit over 500° F), ditto for CPVC, PVDF and the fluorocarbons.

A 'liquid weld' that you mention is rather strange ... but not for acrylics (which can also be welded and interwelded to PVC) and is NOT recommended for your purposes at all!

I suggest you use your local Yellow Pages & look for Companies that do do rotational moulding of Pe tanks ... or go to Harrington Plastics who have an excellent catalogue and who, I'm sure, really KNOW their plastics!

Cheers!

freeman newton portrait
Freeman Newton
White Rock, British Columbia, Canada

(It is our sad duty to
advise that Freeman passed away
April 21, 2012. R.I.P. old friend).




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