Material Failures--Chloride Corrosion of Stainless Steel

In a large number of American homes, hot and cold water are supplied to kitchen and bathroom faucets by braided stainless steel water line connectors. In a significant number those homes, the under-sink space that encloses the braided steel water lines also serves as a storage space, frequently for cleaning products. The subrogation community is gradually becoming aware that this storage practice may be to blame for previously inexplicable water intrusion losses.

Consider the following loss scenario: the insured purchases a new home from a builder-developer, and lives happily and loss-free in that home for two years following the purchase. At the beginning of year three, the insured’s third-floor bathroom floods, causing water intrusion damage throughout the risk and a sizable additional living expense claim. The engineer identifies the source of water intrusion as a braided stainless steel water line that burst at the middle. The water line was installed as a part of new construction only two years earlier, so it has not surpassed its expected useful life, but the engineer notes that there seem to be signs of corrosion around the area of the burst.

Contrary to its name, stainless steel is not entirely stainless; that is, it is not impervious to corrosion. Stainless steel relies on an ultrathin barrier layer of protective corrosion to maintain its resistance to further oxidization. Studies have shown that certain types of stainless steel are especially prone to corrosive pitting when exposed to chlorides. Chlorides are compounds containing the element chlorine which, when it gains an electron and thus a negative charge, forms the chloride ion. Two such compounds, alkyl dimethyl benzyl ammonium chloride and alkyl dimethyl ethylbenzyl ammonium chloride are commonly found in household cleaning products, like toilet bowl cleaner, bathroom cleaning liquids, and disinfecting sprays. It is also understood that when the stainless steel subject to such corrosion is also under tensile or mechanical stress (such as that produced by water-hammer movements), the corrosive effect is accelerated.

Subrogation professionals have seen several water losses caused by bursts at seemingly random locations on braided stainless steel water line, like that pictured above. Forensic experts have learned that many of these failed water lines show corrosion that is consistent with exposure to household chemicals.  Subrogation claims arising from this loss scenario may include product defect claims against the manufacturer of the braided steel water line for a design defect and for its failure to warn the consumer of the dangers of chloride exposure. 

Material Failure--Focus on Cellulose Insulation

This recurring series will discuss various materials, including engineered plastics, woods, metals, polymers, bio-polymers, and other composites, and evaluate real world failure modes and provide practice tips for the recovery professional. The first material discussed is cellulose insulation.

Cellulose is an organic material derived from wood, and commonly used in the building industry to insulate.  Cellulose is commonly seen as blown in insulation in homes and businesses. Blown cellulose insulation is made mostly from shredded newspaper and chemicals to reduce flammability. The composition can vary significantly as to the cellulosic material, and the type and percentage of fire retardant chemicals utilized. Many cellulose companies use a blend of ammonium sulfate and borate. While cellulose manufacturers contend this material is fire safe, even treated cellulose can support combustion and smoldering ignition. 

In the last decade, exactly how cellulose insulation can be ignited has become a growing debate. An older theory claimed that when cellulose was subjected to heat, its ignition temperature was lowered and eventually ignited by that heat source. The current explanation is that through pyrophoric carbonization, where the cellulose first chars and carbonizes, it will self-heat until it ignites. This theory is supported by a 1999 National Institute of Standards and Technology ("NIST") study. Wood chips and whole wood pieces were tested, resulting in a finding that self-heating occurs because of a physical change in the wood which raises its surface temperature and leads to ignition.    

Regardless of the processes, blown in insulation is a competent ignition source. In any fire claim where cellulose insulation may be in the area of origin, steps should be taken to identify the manufacturer, brand/type, and the installer. These parties should be placed on notice if it is suspected the cellulose could have played a role in ignition or fire spread.  If packaging can be obtained, it will typically identify the material type, composition, standards to which the material has been certified, and any warnings.  Samples of cellulose from areas of the home or business that were unaffected by fire should also be taken for future testing.

Decisions should be made whether a chemist or fire spread engineer will be needed. While certain jurisdictions have allowed submission to a jury based merely on cellulose insulation being the most probable fuel for the fire, expert testimony regarding he ignition sequence may be advisable. In circumstances where the fire occurred months or years after installation, having an expert explain the delay in ignition may help the jury to connect the dots.