Technical Bulletin: Effects of Smoke Corrosion to Equipment and Electronics
What is Smoke?
Smoke contains a wide variety of chemicals and by products, many of them aggressive in nature. Examples are hydrochloric acid and hydrobromic acid, produced from halogen-containing plastics and fire retardants, hydrofluoric acid released by pyrolysis of fluorocarbon fire suppression agents, sulfuric acid from burning of sulfur-containing materials, nitric acid from high-temperature fires where nitrous oxide gets formed, phosphoric acid and antimony compounds from P and Sb based fire retardants, and many other compounds. Such corrosion is not significant for heavy structural materials, but delicate structures (thin gauge steel panels, sheet metal, decking, pipe work and wiring) especially microelectronics, are strongly affected. Corrosion of circuit board traces, penetration of aggressive chemicals through the casings of parts, and other effects can cause an immediate (shock to the surface meaning it has been pitted or etched) or gradual deterioration (over time) of parameters or even premature (and often delayed, as the corrosion can progress over long time, continuing on long after the even has occurred) failure of equipment subjected to smoke. Many smoke components (the smoke particle itself) are also electrically conductive; deposition of a conductive layer on the circuits can cause crosstalks and other deteriorations of the operating parameters (for equipment conditions) or even cause short circuits and total failures to electrical devices and controls. Electrical contacts, motor windings, transformers, breakers, switch gear, load centers and control panels can be affected by corrosion of surfaces, and by deposition of soot and other conductive particles or nonconductive layers on or across the contacts. Deposited particles may adversely affect the performance of optoelectronics by absorbing or scattering the light beams.
Smoke residue is acidic in nature and creates corrosion to metal, glass, plastics and of all types of substrates. The heat of a fire opens the pores of substrates and drives the soot particle deeply into the outer layers of the substrates affected. Soot when combined with water or high humidity conditions exponentially increases the acidic strength and thus the damage is very aggressive. Chlorides, sulfides and bromides must be halted by immediate cleaning or at a minimum sealing, immersion or spraying of all surfaces in a protective coating such as oil or varnish until appropriate cleaning can be accomplished. Base line wipe tests and after decontamination wipe test can confirm surfaces has been cleaned appropriately. The temporary coating locks or starves the soot from the oxygen and from the soot particles thus neutralizing it. Rule of thumb- If it is smoke it is acidic. Simple pH tests can help determine acidic levels. Controlling humidity and climate reduces acidic corrosion. Also oil coatings to seal from oxygen and dehumidification all aid in the stabilization steps of equipment until thorough decontamination can be performed. Chemistry, metallurgy and engineering principles are employed to decontamination surfaces to safely reduce acids which ultimately causing pitting, scarring, staining and discoloration. It is possible to reverse corrosion with proper mitigation.
Corrosivity of smoke produced by materials is characterized by the corrosion index (CI), defined as material loss rate (angstrom/minute) per amount of material gasified products (grams) per volume of air (m3). It is measured by exposing strips of metal to flow of combustion products in a test tunnel. Polymers containing halogen and hydrogen (polyvinyl chloride, polyolefins with halogenated additives, etc.) have the highest CI as the corrosive acids are formed directly with water produced by the combustion, polymers containing halogen only (e.g. polytetrafluoroethylene) have lower CI as the formation of acid is limited to reactions with airborne humidity, and halogen-free materials (polyolefins, wood) have the lowest CI. However, some halogen-free materials can also release significant amount of corrosive products. Smoke damage to electronic equipment can be significantly more extensive than the fire itself. Cable fires are of special concern; low smoke zero halogen materials are preferable for cable insulation.
How does it affect equipment and electronics?
Many times valuable equipment and electronics may be effectively restored and repaired for re-use. Fast action is requried to remove power supplies and energy sources that may damage sensitive equipment, mitigate climatic changes and outside inhibitors and contamination such as water, dust, soot or foreign objects in or on a system is vital to the recovery and operation of equipment. Electrical gear, power distribution and generation equipment should only be serviced by properly trained techs using correct tools, testing and recertification methods for working with OEM consent and approvals prior to being put back into use or re-commissioning. Knowledge of restoration methods is necessary to complete a proper recovery of electronics and switch gear after restoration back to pre-loss and prime operating condition.
Testing for smoke
Material Characterization Tests are very expensive Material and combustibility profiles of the selected materials were developed to document the traceability of the materials investigated. The material and combustibility profiles include material chemistry, thermal response to heating, and the potential heat value. The test methods characterize the materials include the following:
Differential Scanning Calorimeter (DSC);
FT-IR for materials chemistry (plastics only);
Thermo-gravimetric Analyzer (TGA) with smoke cell and gaseous FT-IR attachments; and
Oxygen bomb calorimeter
Spectrometer testing, air quality and waste stream tests are most cost effective and may need to be performed by certified industrial hygienists to ensure safety of employees and help determine what the actual contaminate present as well as testing of waste water disposal form the job site.
The importance of proper insulation resistance testing and techniques are applicable after flooding, fire or lighting damage events which impact the wiring system of a building. Electro-Mechanical Recertifiers, LLC. provides technical and engineering power related reports to insurance carriers and risk managers who have experienced an event affecting buildings wiring system, power distribution gear or electronics and equipment from computers and IT components to compressors and all types of machinery.
Unless rated for use underwater, wire that has been submerged and completely soaked wire will not pass minimal insulation requirements. Water under pressure almost always permeates common dielectric materials like vinyl, plastic and rubber. Insulating materials can sometimes be dried out and after proper testing can be salvaged and brought back to original quality. When the wiring is clean, dry, and tested to confirm that any current leakage meets the requirement, then the wire may be put back into service. Experts are aware of electrical devices and conductors that can be cleaned and tested, and those that need to be replaced. Smoke or heat damaged wire may have other problems. Smoke contains soot that is corrosive and can break down the polymers and compounds in PVC, rubber and other materials used in insulating jackets. This soot can be highly corrosive and needs cleaned and tested or may be at risk of critical failure in the future. Improper cleaning and painting of outer jackets may harm the outer insulating cover and result in premature failure. Excessive heat can cause thermal damage meaning the thermal set temperatures of the jackets substrate during manufacture may have been physically or chemically altered and at certain levels the conductor may also be affected by the heat damage. Physical inspection and electrical testing are important to ensure that the thermal damage has not melted and carbonized the insulation surrounding the conductors that will eventually result in a dead short.
Machinery requiring restoration also needs a vast array of specialists on the team who perform work functions on them to ensure its proper recovery. Inside the technical area are electrical journeyman, mechanical specialists, piping experts, machinery mechanics, laser leveling and plumbing trades as well as millwrights, machinists, electronics technicians, insulators, fitters/welders riggers, crane operators and electromechanical restoration specialists involved in the recovery of various many equipment types. At various intervals our work requires different electro-mechanical qualified tradesman. Equipment requires precise laser leveling, vibration analysis, and decibel level measuring, adjustments and fine tuning as well as work area lighting reports, PLC programming, IT repair techs, process monitoring, third party motor and power testing. Both the mechanical and electronics restoration skill sets are highly needed specialty areas of technical restoration common in most equipment types. Most of today’s equipment types are electronic in their control systems (some simple and others have complex controls) such as push bottom operational, relay logic control panels and others are PLC’s used to automatically control the electronic sequence of the equipment’s various operations. Working to the OEM’s standards and factory specifications can ensure a complete restoration process and acceptable product in the end.
Affected equipment should have acclimatization controls including temp. HVAC and dehumidification in place to control high ambient temperature and moisture levels if it was wet or smoked. Also the use of desiccant packs is often part of the process. Also included as an emergency preservation measures is the application of corrosion inhibitors and moisture displacement agents. The equipment left unattended and sitting in corrosive conditions will cost more to restore and repair. If pre-treated and climate controlled, these actions allow the insurance company time to review their questions and decisions without further risk of loss. The application of these services stops the degradation from further affecting the equipment. If these services are provided it is proven that final repair costs will be much less and the chance of restoration is much better. I left untreated a lot of components may need replacement meaning more time and money are added to the end process for final recovery. Equipment that stays covered in corrosive soot and high moisture needs to be mitigated fast as it a hundred times more acidic in nature than is dry soot. These conditions are perfect for flash rusting as air oxidizes quickly on the ferrous metal parts and corrosion will also form on all non-ferrous metal components such as circuit boards, contactors, relays, control panels and motor coils. Tenting or encapsulating is always an effective measure to control the environment.
Mandeville, LA 70471