Prioritizing Safety in a Cleaning Environment

Safety is and will always be job number one and is critical to the success of any process line. Regardless of size or degree of automation, this imperative extends to the selection and use of various types of chemical process baths and treatments. For the use of all surface preparation materials, adherence to vendor recommendations, drum labels, safety data sheets, proper protective clothing and in-house safety training are strongly recommended.

Two types of product concentrates — liquid and powder cleaners — are widely used for soak and electrocleaning. These systems contain similar additives including alkalinity builders, buffers, surfactants, wetting agents, descalers, water conditioners and inhibitors. Their cleaning dynamics and bath service lives are comparable, and their upfront operating costs are also similar.

However, this is where relative similarities end. Liquid cleaners are more economical because they offer the user less sludging, simple chemical makeup, ease of addition and higher amenability to waste treatment than powder cleaners. On the surface, these handling features also make liquid cleaners inherently safer.

Storage and use for liquid cleaners

Liquid cleaners were developed to meet the same rigorous cleaning applications as powder blends. In fact, concentrated liquid blends offer significant safety advantages to finishers, including:

• Supplied in robust polyethylene (PE) drums and bulk tote sizes, liquid cleaner containers withstand handling better than fiber drums. Totes are placed inside a protective mesh metal cage.
• The concentrated liquid is a stable blend. Hence, there is never any clumping or hardening with time. However, protection from freezing temperatures might be required.
• Liquids eliminate the problem of dustiness. However, spillage can be a problem that potentially causes burns, rashes and slippery floors, which can occur with powder blend cleaners as well.

• Additions can be made directly from a drum pump to the process tank, which eliminates exposure. This method also provides a quick, uniform dispersion of the added cleaner to the process tank. The drum or tote can be stored safely away from the cleaner tank and the contents automatically added by a pump activated by a conductivity meter.
• Liquid blends are 100% mixed upon initial blending and stable when stored as recommended. Moderate, thorough mixing of additions in the tank are simple, while minimizing splashing.
• Tank cleanout is simpler and safer compared to powder cleaners because of the potential for significantly less sludge removal in the liquid cleaner tank.
• Empty drums may be recycled. Most deposit totes are returnable.

Liquid cleaners are implemented in an increasing number of cleaning lines. Although total safety is never 100% guaranteed, the use of liquid cleaners provides the finisher with overall significant safety advantages when compared to powders.

Storage and use for powder cleaners

Powdered cleaner efficacy should in no way be minimized. For decades, and for the foreseeable future, powder cleaners comprise the first critical step in many process cycles. Acknowledging the following safety dos and don’ts — and by observing Occupational Safety and Health Administration (OSHA) regulations and others — finishers will continue to integrate them safely and successfully.

• Powdered cleaners are typically supplied in fiber drums. Mishandling or poorly storing these drums can cause them to crack, spilling their corrosive contents and presenting hazards to personal safety.
• Aging drums of opened or unopened cleaner tend to harden because of moisture absorption. Clumping of product concentrate creates difficulty in removing the contents when making additions. In fact, some shovels and pickaxes work to remedy this situation, causing broken clumps to fly in all directions.
• Don’t suspend drums above a tank. Cutting away the drum results in “boulders” of cleaner tumbling into the process tank, causing a hazardous situation.
• Manual additions might give rise to dustiness, with fine powders settling on unprotected skin, causing burns and rashes.
• Additions must be made in gradual steps to avoid possible splashback because of localized boiling of added cleaner.
• Good mixing is essential to prevent formation of undissolved clumps that settle to the bottom of the tank. Care must be taken to avoid splashing and spray.
• Cleaner spilled on catwalks pick up moisture, resulting in a slippery surface.
• Any undissolved cleaner, particularly when accompanied by sludging, takes time to clean out, which further exposes workers to hazardous conditions.

Liquid acids

Liquid acids and powder acids are essential to cleaning, descaling, de-rusting and overall activation of the surface before plating or other finishing processes. Both adequately condition the surface with one system employing generic acids and the other providing salts of acids that ionize when dissolved in water.

Liquid acids are used daily in many finishing and waste treatment applications. Trained personnel have learned to use proper techniques and precautions to handle and use these acids safely. Generic acids will always have a place in metal finishing because of their importance to specific surface treatments, primarily in conditioning and activating the base metal surface.

Many products are defined as liquid acids, including hydrochloric and sulfuric acids, and to a lesser degree phosphoric and acetic acid, as well as brand blended liquid acid concentrates that provide a product that is easy to handle and dispense.

Acid salts are blended to offer additional acid accelerators in the form of chlorides and fluorides. These agents also ionize in solution, resulting in hydrochloric and hydrofluoric acids. A single concentrate can eliminate the handling of two or three separate generic acids, which is another safety benefit.

Powder acids

Powder acids were specifically developed to increase the effect of acid treatments for safer handling. This acid type offers several advantages with respect to improved safety.

Upon dissolution, acid salt ionizes to generate active acid in the bath. Sodium bisulfate, the acid salt of sulfuric acid, is a common powder acid. Powder acids eliminate the handling of sulfuric acid and its accompanying exothermic heating.

Unlike liquid acids, powder acids might contain surfactants and wetting agents. These agents enable improved penetration for surface action, which in turn can result in using less product compared to a higher concentration of liquid for the same application. The less time spent handling hazardous material, the safer the situation.

Surfactants and wetters in powdered acids form a stable, light foam blanket, which may eliminate more than 99% of the potentially corrosive fumes and mists.

Unlike liquid acids, powder acids might contain surfactants and wetting agents that enable improved penetration for surface action. This can result in using less product compared to a higher concentration of liquid for the same application.

Powder acids might contain special inhibitors to prevent immersion deposits, thereby extending the bath service life. These products are also buffered to provide longer functioning acid action over time. Less frequent solution dumps mean less handling.

Other safety concerns for acids

Both acid types can be dangerous. Therefore, safety is of the utmost importance for anyone handling these chemicals.

Corrosiveness, which can result in rapid, severe burning of exposed skin and possible hydrochloric acid concentrate fumes, is a hazard. Corrosive fumes are also emitted during pickling, which must be properly vented. The branded liquid acids are typically non-fuming and although aggressively corrosive they are less so compared to generic acids.

Sulfuric acid is especially exothermic, rapidly emitting lots of heat that can result in localized boiling and splashback. Additions to tanks must made gradually to cold water with good mixing. Branded liquid acids are blended with the sulfuric acid component having been already added, thus eliminating the extreme heating that occurs while handling generic sulfuric acid.

Extreme care is necessary to prevent potentially catastrophic accidents, particularly when mixing acids is required. For example, de-smutting aluminum, which requires handling nitric, sulfuric, and hydrofluoric acids in specific combinations, should be complete with careful attention.

Empty carboys, drums and totes of acid must be returned for refill promptly. Reducing hazardous clutter is imperative in maintaining overall safety on the shop floor.