ForgeFix Machine Screw Pozi CSK ZP - ForgeFix 25MSCSK650, These Forgefix Pozidriv Machine Screws are designed for use with nuts or pre-tapped holes. They are Zinc plated for increased corrosion resistance. The countersunk head is suitable for pre-countersunk holes or when fastening to timber to leave a flush surface. Ideal for use in many DIY, ironmongery, electrical and plumbing applications. 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 fac