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Name: Byron
Status: educator
Grade: 9-12
Location: AL
Country: USA
Date: Winter 2012-2013

I am working with students with a plasma cutter. I teach Industrial Systems. After cutting the parts on the CNC plasma cutter we put them in an acid bath at industry standards recommendation. The reasoning is the removal of the "Mill scale" on the outside of the steel part. It also will eat the dross (the part of the steel left attached to the bottom of the steel part when the cut is being evacuated with the air). This is extremely labor saving. The acid we use is a 50% acid 50% water muriatic acid mix. I know it will corrode metals with its fumes. I currently am not using a great method for keeping it safe and would like recommendations how I could move this acid bath indoors and ventilate it so I could lock it up to keep an accident from happening. What sort of ventilation would be required and how can I lock it and still keep it from evaporating out under ventilation?

Hi Byron,

A common way to reduce evaporation and reduce fumes of acid baths such as the hydrochloric acid "pickle" you are using, is to float a layer of hollow polyethylene balls on the surface. Covering the surface with a layer 2 or 3 balls deep will dramatically reduce evaporation and the production of fumes. Polyethylene is unaffected by strong acids. The balls remain permanently floating, and you simply plunge the parts to be cleaned through the layer of balls, into the "pickle".

One source of these balls that I am aware of is....

Here is the specific page from their catalogue.....

Hope this helps, Bob Wilson

Hi Byron,

Thanks for the question. Before proceeding further, I would like to steer you towards reviewing the Material Safety Data Sheets (MSDS) for muriatic acid, also known as hydrochloric acid. These sheets provide important safety information when using muriatic acid. Certain states require that these MSDS sheets be made available to workers using the chemicals.

Muriatic acid is quite corrosive to metals, skin, and mucous membranes (e.g. throat and eyes). If you are to use a respirator, it would need to be able to handle acid gases as well as provide eye protection. I personally use a plastic 5 gallon bucket with a plastic lid. I use a ventilation system called a fume hood--it works quite well. However, that may not be available in your facility. I would recommend storing the acid solution on a cart so that it can be transported outside for the dipping treatment. The cart can then be locked up inside a closet.

I hope this helps. Please let me know if you have more questions. Thanks Jeff Grell

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