Welding and Protective Coatings

There are many different types of welding and associated processes.  The most common types of welding are arc welding, which includes “stick” or shielded metal arc welding (SMAW); gas-shielded methods of metal inert gas (MIG), tungsten inert gas (TIG), plasma arc welding; submerged arc welding and oxy-acetylene welding.  Welding smoke, generally, is a mixture of very fine particulates (fumes) and gases, including metal components such as iron, manganese, chromium, nickel and zinc and non-metals such as ozone, fluorine compounds, nitrogen oxides and carbon monoxide to name a few.  Of these metals, manganese, chromium, and nickel typically present the most significant health concerns.  As individual metal constituents may vary widely in the steel alloy and the electrode, it is important to examine the safety data sheets for all products being used.  As the percentage of any one constituent metal increases, so does the potential exposure during welding.

However, there may be exposures that are not expected before the welding, cutting or brazing operation begins.  It is well-known that torch cutting or welding on surfaces that are coated with a lead based paint is hazardous.  The heating of the paint releases lead fumes and creates a potential exposure hazard to the employee performing this work. However, even if lead is not present, protective coatings on steel may be another source of exposure to fumes and gases during welding, brazing and cutting.  This is often overlooked with welding operations, particularly in repair or renovation operations.  These may include welding, brazing or cutting on chemical-containing tanks, metal parts with protective coatings such as plastics, Teflon, paints, etc.  In some cases the Safety Data Sheet on the coating may suggest that the material is not hazardous.  However, when the material is heated by welding, brazing or cutting, hazardous materials may be off-gassed including organic compounds, mineral acids, metals, and gases such as carbon monoxide, sulfur and nitrogen compounds.  The Cohen Group has been asked to respond to worker illnesses or complaints that are related to a coating that was on the steel being welded or brazed.  In some cases the steel surface appears clean but may contain residues.

Protective coatings may also be flammable.  Torch cutting or welding on these paints may cause a fire, creating a physical hazard to workers and bystanders and possible release of materials to the air.  Due to the multitude of health and safety hazards that employees can be exposed to from welding operations, all protective coatings should be removed prior to welding and/or torch cutting.  An often overlooked Cal/OSHA standard covers this topic (8 CCR §1537 Welding, Cutting and Heating of Coated Materials).  This standard requires removal of protective coatings at least 4 inches from the area of heat application or the use of ventilation or supplied air respirators.  It is best to remove the coating to a distance away from the weld or cut, where the temperature won’t go above the point where the material starts to break down.

Adequate ventilation will generally reduce exposure to the various metal constituents from welding.  Ventilation is important when welding in hard to reach or tight spaces with limited air flow.  Proper ventilation may be achieved by good natural (or general dilution) ventilation or through use of a local exhaust system.  If ventilation is not feasible then consider respiratory protection.  The Cohen Group can assist you in reviewing proposed work procedures and possible airborne contaminants prior to work that involves welding or torch cutting on previously painted or coated surfaces and determine an industrial hygiene plan including air monitoring to protect workers and bystanders.