Most aren’t aware that deck collapses are up 20% since 2007. Since this time, the composite decking industry has rapidly grown, with these generally longer lasting products. Fortunately, most are preventable. Unfortunately, most composite manufacturers, chemical manufacturers, distributors, retailers & owners ignore the risks of recommending selling & using corrosive to metal cleaning chemicals to clean composite decking, especially on a routine basis. These cleaning chemicals generally contain oxalic acid or sodium hypochlorite.
There’s likely good reason USP® Connectors has disclosed the “causes of external attack by chemicals like chlorine bleach” & Simpson® Strong-Tie has disclosed the “corrosion risks” of “cleaning chemicals”! These are the two largest structural metal decking hardware manufacturers & commonly recommended in composite manufacturer “Installation Guides” and/or used in the construction of all decks! It is a good idea to check your specific decking hardware manufacturer literature or call & ask the following questions?
Is it safe to use corrosive to metal cleaning chemicals, especially on a routine basis, that will likely come into contact with structural metal decking hardware?
Will the use of corrosive cleaning chemicals void the manufacturer warranty of the structural metal decking hardware?
Should the structural metal decking hardware be replaced when corrosion is noticed?
Trex® where “sodium hypochlorite” was recommended to be routinely used, “Spring and Fall”, in their “Mold Technical Bulletin” until completely mold infested! Notice the black spots growing into giant mold colonies, taking over the entire boards & the red rust corrosion bleeding from the screws fastening the composites to the substructure. It will require another cleaning chemical to remove the rust stains from the composites that is non-compatible. Unfortunately, the corrosion is irreversible, & these items should be expensively immediately replaced, as they are unsafe! What do you think this corrosive to structural metal cleaning chemical has done to the non-visible joist hangers, nails or screws under the decking? Will this deck collapse when under load from generally people?
There is likely good scientific reason related to corrosion to why one of the most well-known sodium hypochlorite-based cleaning products, “CLOROX® OUTDOOR BLEACH CLEANER”, has disclosed “DO NOT USE THIS PRODUCT IN FULL STRENGTH”, “Always dilute strictly in accordance with label directions” for “galvanized” “materials”, “Strength” “Low (Green)” “Dilution” “1:21” “6oz (3/4 cups) of product to 122oz (15 ¼ cups)” of water. This product label directions then go on to state “Prolonged contact with metal will cause pitting and discoloration.”, such as black or red rust stains in composites around metal structural decking hardware! Most retailers, composite & chemical manufacturers have recommended & sold sodium hypochlorite-based products that are to be used at greater sodium hypochlorite concentrations, especially when they no longer bleach out common molds after being routinely used. At least one product for cleaning decking label directions recommend their product be “applied at full strength”, which is greater than what CLOROX® discloses, while others disclose “may be corrosive to metals”, such as the product that contains a polluting phosphate, which is a fertilizer & helps plants/molds/algae to rapidly grow!
“Galvanized” “materials” are almost always used in the manufacturer of joist hangers & nails, to structurally support & hold together almost all composite decks, due to these items being generally recommended by composite deck manufacturers in “Installation Guides”, often in the same brochure as the “Composite Deck Care & Cleaning” literature. The rare exception is where more expensive stainless-steel joist hangers & fasteners have been used. Stainless-steel is commonly used to fasten composites to the structure under it, with screws, especially when hidden fastener systems are used. As GRK Fasteners® has stated “Chlorine-based bleaches and cleaners are not recommended for most deck fasteners, our Climatek coated products included. Our PHEinox stainless steel fasteners can handle these harsh chemicals much better, but the use of such chemicals is not recommended in the first place; they are harsh on the decks themselves and joist hangers and other such deck hardware.” While stainless steel is generally more resistant to corrosive cleaning products than galvanized metal, it is not immune to corrosion, as it too “pits”, resulting in the loss of structural value when corroded with corrosive cleaning chemicals.