Porous implant material having a plurality of metal bodies having different porosity rates which are bonded with each other at bonded-boundary surface F parallel to a first direction, wherein: a bonded body of the metal bodies has an entire porosity rate of 50% to 92%; the metal body having higher porosity rate is a porous metal body having a three-dimensional network formed from a continuous skeleton in which a plurality of pores are interconnected; the metal body having lower porosity rate has a porosity rate of 0 to 50% and an area-occupation rate of 0.5% to 50% in a cross-section surface orthogonal to an axial direction which agrees with the first direction along the bonded-boundary surface; and a compressive strength compressing in a direction parallel to the bonded-boundary surface is 1.4 times to 10 times of a compressive strength compressing in a direction orthogonal to the bonded-boundary surface.

Red rust staining of Al/Zn coated steel strip in acid rain or polluted environments can be minimised by forming the coating as an AlZnSiMg alloy coating with an OT:SDAS ratio greater than a value of 0.5:1, where OT is the overlay thickness on a surface of the strip and SDAS is the measure of the secondary dendrite arm spacing for the Al-rich alpha phase dendrites in the coating. Red rust staining in acid rain or polluted environments and corrosion at cut edges in marine environments can be minimised in AlZnSiMg alloy coatings on steel strip by selection of the composition (principally Mg and Si) and solidification control (principally by cooling rate) and forming Mg.sub.2Si phase particles of a particular morphology in interdendritic channels.