Alloy chain, normally sold as grade T or grade 800 is typically 2 to 3 times stronger than the chain normally used in moorings. Occasionally, you see this chain and more often the associated fittings making its way onto moorings when parts get substituted as mooring components wear. Unfortunately this high-strength chain undergoes chemical changes when immersed in “aqueous chloride solutions” aka seawater. The process is known as hydrogen embrittlement makes the chain susceptible to failure under shock loadings which is generally considered to be a bad thing for moorings. Suspiciously small shackles, hammer locks and oblong lifting links are all usually grade T and should be avoided in moorings.