In our final installment on safety,* we continue our look at solutions and chemicals, and add some dos and donts about equipment and procedures.

Tin-lead Plating Baths

Tin-lead plating solutions are also known as "solder plating" solutions. As their name implies, tin-lead plating solutions contain lead compounds. Such chemicals can cause lead poisoning if inhaled, ingested or absorbed through skin.

Lead is a cumulative poison. This means that small amounts entering your body stay there and add up, until eventually, you become very ill or die. If your plant performs soldering or other hot operations, such as brazing on lead-containing materials, the fumes generated are toxic and should be ventilated.

Anodizing Baths

There are several types of anodizing baths, each usually posing a different level of hazard.

Sulfuric acid-based baths are the most commonly used for both regular and hardcoat anodizing. The health hazards posed by these baths are related to their acidity and to the fact that they are operated with air agitation, which presents a misting problem that is normally controlled by the ventilation system.

Sodium Hydroxide/Sulfuric Acid

For pH neutralization, waste treatment systems use sulfuric or hydrochloric acids and caustic soda, the common hazards of which we discussed in October.

Sulfides

Some waste treatment systems use sulfide-containing chemicals to help precipitate the metals out of the wastewater.

Chemicals containing sulfides have similar hazards to cyanides. Sulfides also make a gas if accidentally mixed with acid. This gas is even more poisonous than cyanide and smells like rotten eggs.

If you work in an area where sulfides are used and you smell rotten eggs, leave the area immediately and warn as many other workers as possible on your way out!

Sulfide gas can deaden your sense of smell, too. If you smelled the gas, but a short time later cant smell it, there is a good possibility that your ability to smell it has been eliminated by the gas itself. Many sewer workers have died because they thought the sulfide gas had gone away, when in reality, it was their sense of smell that had left!

Unlike cyanide, the only antidote for sulfide-gas poisoning is fresh air, but its obviously best not to have the problem in the first place. Do not use or store sulfides near acids.

Reducing Agents

Some waste treatment systems use chemicals that are classified as reducing agents. Reducing agents are commonly used to convert hexavalent chromium to trivalent, for precipitation. Sodium bisulfite and sodium metabisulfite are two of these.

Reducing agents can cause explosions if accidentally mixed with oxidizers in large quantities Some reducing agents, such as bisulfites, give off irritating fumes that can be toxic in high concentrations. They should be used only with good ventilation.

Another commonly used reducing agent is sodium hydrosulfite. This chemical can catch fire automatically, if you allow it to become wet. No match, spark or flame is required; the fire starts by a chemical process.

Chemical Storage

Because chemicals have the ability to react violently when contacted with other chemicals, extreme care must be taken to store reactive chemical groups apart from each other.

Cyanide-containing chemicals should be stored by themselves, or with alkaline chemicals. Do not, however, store sodium hypochlorite in the same area as cyanide, even though it is alkaline.

Acids should be stored only with other acids. Acids that are oxidizers should be stored separately, with other oxidizers. Never store acetic acid in the same area as nitric acid, because they are dangerous when mixed.

In basic chemistry, we call a chemical an organic if it contains the carbon atom. Storage rules for organic-containing chemicals will vary greatly, because there are so many different chemicals that fall into this class. Its best to follow the instructions on the Material Safety Data Sheet (MSDS) for each organic chemical. Common organic chemicals used in metal finishing include degreasing solvents, paint thinners, brighteners and numerous additives identified by trade names.

Cleaners and other caustic-containing chemicals are usually stored together, but away from other groups.

Flammable materials must be stored in specially approved containers and rooms meeting local fire codes. Metallic containers that contain flammables must also be properly grounded against the risk of ignition by electrical spark.

Liquid chemicals must be stored in diked-off storage areas and should be separated, using the storage rules outlined above. Do not store liquids in the same area where you store solids.

Equipment Malfunctions & Hazards

Surface finishing equipment can pose injury problems in many ways, depending on its type, condition and whether or not you use it for its intended purpose.

Always be sure to follow the equipment manufacturers instructions carefully. Never modify machinery for any reason, without obtaining both instructions and permission from its maker. Modified equipment that no longer meets manufacturer specifications is the cause of hundreds of accidents annually. If you have an operation that is performed frequently or regularly, get the machine designed to do that work. The money invested will be nominal compared to the cost in loss of an eye, or a limb, or a life!

Electrical Hazards

Metal finishing shops may use rectifiers and other electrical equipment that can have extremely high-voltage input. Unless you have had specific training from the manufacturer, leave rectifier maintenance to him or his technicians. All electrical equipment is subject to OSHA lockout-tagout rules. If you are going to perform any service on electrically operated machinery, you must follow the lockout/tag-out procedures set forth in your companys compliance program.

In general, a lock-ou/tag-out rule requires you to disconnect the power to the equipment youll be servicing, and then to secure and label the disconnect, so no one but you can turn the power to that device back on before youre done.

Automated hoists travel set paths that may go right across your head or other parts of your body, if you happen to come between a hoist and its programmed route. Always let operators of automated equipment know where you will be, and lock-out/tag-out the machinery before starting to work on it.

Most surface finishing/coating processes operate at low voltages typically 4-1 2V. Some, however, operate at comparatively high voltages. A number of anodizing processes operate at 100V, for example. For this reason, you should never assume that it is OK to touch the workbars on top of the tank, unless the power is off and locked/tagged.

Filters/Pumps

Filters and pumps usually contain the same chemicals as the tank they are servicing. It follows, then, that they also contain the same chemical hazards. In addtion, these devices operate under pressure, so a small leak can spray a liquid out of a filter or pump over a long distance.

You should wear the same protective gear when working around these pumps and filters as described by the MSDS for the chemicals in the tanks.

Confined Spaces

A confined space is any area in which you might place your body, which you cannot easily exit, without a ladder, co-worker, harness or other type of assistance. Many surface finishing shops use very large tanks for processing or waste treatment. Others employ deep pits or in-ground tanks. These are common examples of confined spaces. The hazard of a confined space is obvious: What would happen if you got hurt while in such a place?

For this reason, every company that has tanks, pits, ductwork or any other space a worker is required to enter, must assess that spaces potential for becoming a trap. If your company has confined spaces, it must also have a confined space entry program, detailing how you are to be protected.

In general, you should never enter any confined space without a harness or other device that will allow you to be removed by workers stationed on the outside of that confinement. And, if that confined space contains hazardous air contaminants, the company must supply and you must wear a respirator or other approved breathing apparatus. You should never enter a tight spot unless there is at least one or more co-workers nearby who are capable of pulling you out, if an emergency arises.

No worker should be permitted to enter a confined space without specific training and verified knowledge of the companys policy on working in such surroundings.

Working Alone

You should never work in any area containing hazardous chemicals or in a confined space, even if that confined space contains no chemicals. Unless there is at least one other knowledgeable employee who is aware of where you are, what you are doing and how to handle a possible injury or chemical emergency, do not enter an area.

Falling Into a Tank

There have been incidents of workers having fallen into large processing tanks because they were working or walking on top of the tanks without a safety harness. Such a fall can result in serious injury or tragedy. Dont be foolish. Dont walk on top of any tank that you or part of you can fall into. Always wear a safety harness that will prevent you from falling in, and be sure someone is standing by, in case you get in trouble.

Safety Equipment

Everyone should know what safety equipment is appropriate for which job, and when to wear or use it. If you see a co-worker without proper protection, it is your duty to speak up and remind him that he is endangering himself, and you.

You should also be aware that some chemicals can eat through the wrong protective equipment. Be sure that what youre wearing is resistant to the chemical youre using. The MSDS and your OSHA safety program are guides to protective gear.

If your plant uses respirators, you must also be provided with training in the care and use of these devices. Your company must have both formal training and written respirator programs. A respirator can actually increase the danger to you and your health, if it is not used properly.

Fire Hazards

Surface finishing shops house many chemicals that are combustible. And because these facilities often use plastic tanks and plastic ductwork and containers, along with paper and wood products that readily burn, there is a great potential for a serious fire. For this reason, housekeeping is extremely important. A shop that keeps anything that can burn away from sparks, flames and oxidizing chemicals stand a much better chance of avoiding such fires. Past experience has shown that surface finishing shop fires start in one of several ways:

1. Electrical Heaters in Plastic Tanks

Electrical heaters can set a plastic tank or lining on fire if the liquid level in the tank drops low enough to expose the hot part of the heater to the plastic. Many shops over the last few years have had such fires. Some manufacturers have installed temperature sensors that shut down the heater if it becomes too hot. These are a good idea. The best way to prevent such fires is to make sure the heater is always under liquid. Never operate the heater for a long period of time (such as overnight) unattended.

2. Fine Metal Powders

Fine metal powders can catch fire spontaneously, if they become wet and are then allowed to dry. No match, spark or flame is needed.

Typical surface finishing operations that involve the generation or use of metal powders include zinc dust treatment and some electrolytic wastewater purification systems.

To prevent a fire from wet metal dust, you must either keep it wet, or convert it to a state in which it is not a dust. For example, if you can compress the dust into a pellet or ball while it is wet, its tendency toward combustion will be greatly reduced. Zinc dust from treating a plating solution should be kept wet and introduced into the plants waste treatment system in very small quantities, over several days.

3. Electrical Fires

Surface finishing shops use a lot of electricity often in humid and corrosive atmospheres. Electrical short circuits can lead to fires. To help prevent such fires, be sure to inspect your rectifiers, switching boxes, motor controls and all other electrical fixtures on a regular basis. Have sodium bicarbonate strategically located throughout your plant so that an electrical fire can be put out quickly. Never use water or any other incompatible substance to extinguish an electrical fire. Take an extra second or two to read the label on the fire extinguisher before you use it on a fire, to make sure it is safe for an electrical fire or whatever type of fire youre trying to put out. Many are not.

4. Oxidizers

Many people do not realize that oxidizers, such as chromic acid, can cause such combustible materials as fabric paper, wood and organic solvents to catch fire. By the time they learn, its too late. Do not allow contact between oxidizers and things that can burn.

5. Hydrogen

We know of one fire that involved hydrogen which had accumulated in the ceiling of a plating shop. The hydrogen originated from the electrocleaners, acid pickles and plating tanks that tend to generate this gas. Eventually, the hydrogen in the ceiling reached a high enough concentration (known as the "lower explosive limit") and caught fire or exploded. The fire was so intense that the entire building was gone in less than three minutes.

The gases leaving processing tanks and generating hydrogen gas should be adequately ventilated. And the air in the processing department can be exhausted with ventilator fans.

Foam blankets on electrocleaning tanks are notorious for producing minor explosions when they trap hydrogen and are then set off by a spark from a part that touches a cathode bar. While this may only be a minor fire hazard, the explosion makes a noise that far exceeds OSHA regulations. Elevating the cathode bar, turning the rectifier off before introducing parts, and use of low-foaming electrocleaners can eliminate this danger.

We have covered only a few of the safety hazards that you might encounter in a surface finishing shop. There may be many more in your shop, and they may be far more complex. You should use the basic information provided here as the beginning of a full understanding of these dangers and how to work safely among them. Under OSHA regulations, your company must tell you about the chemical hazards in your workplace The company also must provide a workplace that is reasonably safe. But ultimately, it will be up to you to put what you learn about safety to good use.