ForgeFix General Purpose Pozi Screw Round Head TT ZP - ForgeFix RH18ZP, These Forgefix General Purpose Pozi Screws with round heads are zinc plated finish for increased durability. They are versatile screws, suitable for use in and with many materials. Ideal for use in many ironmongery, electrical and plumbing applications. Can be used with various screw cover caps. Zinc coatings prevent oxidation of the protected metal to create a longer lasting finish. It does this by forming a barrier and by acting as a sacrificial anode if this barrier is damaged. Zinc oxide is a fine white dust that (in contrast to iron oxide) does not trigger a breakdown of the substrates surface integrity as it is formed. The zinc oxide, if left intact, can act as a barrier to further oxidation, in a way similar to the protection afforded to aluminium and stainless steels by their oxide layers. The Pozidriv screw is similar in appearance to the classic Phillips cross-head, but in fact is very different. The Poz