IAQ Concerns Stemming from Acid Bath Fumes

What is an Acid Bath, Exactly?

Metal corrodes; that’s just chemistry. At home, we can drop a rusty screwdriver or gardening tool in a container of white vinegar and leave it overnight to loosen the rust. But in manufacturing, large-scale metal oxidation requires an industrial acid bath. Correctly managed, acid baths can remove unwanted coatings from valuable metal parts. Ill-managed, this process can cause significant indoor air quality problems that can make workers sick.

The basic science behind rust and corrosion is that ferrous metals, such as iron and steel, can rust. Non-ferrous metals, such as copper and aluminum, can corrode but will not rust. Regardless of what covers a piece of metal – dirt, grime, rust, or oxidation – acid washing helps remove it and prepare it for industrial use. This process is a critical step in readying parts for assembly, ensuring proper function of electronic components, and prepping surfaces for applications like electroplating, painting, and coatings.

Industrial Acid Washing

Many industries utilize acid washing as a basic method of preparing metal for use by cleaning, removing rust and oxidation, and creating a smooth surface, high-quality finish, and structural integrity.

Applications include:

• Electroplating or preparing gold and silver for crafting fine jewelry
• Painting or coating auto parts and aerospace components
• Etching or creating circuitry patterns in PCBs to guarantee proper functioning of electrical workings
• Removing scale and rust (pickling) from iron and steel before galvanizing to use in construction

Acid Washing Chemicals

The chemicals used in an acid bath will depend on the metal needing cleaning and the type of corrosion requiring removal. Hydrochloric acid, for example, is ideal for bronze and other copper-based alloys. Sulfuric acid is often the initial chemical used to clean gold. Stainless steel is best washed in a nitric hydrofluoric acid wash.

IAQ Problems

As with many manufacturing processes, the practice of using an acid bath can create problems with indoor air quality. Emissions from chemicals such as hydrogen chloride (HCI), nitrogen dioxide (NO2), and hydrofluoric acid (HF) have the potential to make workers sick. The toxic fumes and chemical mists can be inhaled and absorbed into the skin. In both instances, a worker’s health and well-being will be at risk.

Potential Health Hazards

Whether a worker’s occupational exposure to chemical fumes and mists is acute (short-term) or chronic (long-term), the negative health effects can be significant.

Acute exposure can cause burning eyes, skin rash, headache, dizziness, nausea, vomiting, coughing, and shortness of breath.

Chronic exposure can cause all of the above plus significant respiratory issues such as chemical pneumonia, asthma, and bronchitis.

Absorption through the skin can lead to systemic toxicity that can affect liver and kidney function. Inhalation – depending on length of time and level of exposure – can pose cardiovascular problems and in some cases, cause cancer.

Indoor Air Quality Solutions

Indoor air pollution associated with industrial acid washing can be avoided if countermeasures are employed.

First, proper workspace ventilation is paramount in controlling toxic emissions created by chemical offsetting from acid baths. Secondly, employers should require workers to wear personal protective equipment, such as goggles and facemasks. Lastly, businesses should use fume extraction to remove toxic emissions at the source – before they can pose an occupational risk.  

AIRSInc. has air-cleaning products that can help. Our top Extract-All® products for source capture of acid bath fumes include models SP-800, SP-4000BWC, and SP987-2. Contact us today for a free consultation with one of our clean air specialists to learn which air cleaning product is right for your company.