Decided to go with threekim after few quotations from other contractors are about the same price. And threekim has good reviews here in lowyat.

Taking measurement this Saturday

powder coated mild steel or Stainless steel will be good enough.

aluminium waste of money I think, if the grille is supposed to be your security barrier. https://www.rsgsecurity.co.uk/blog/more-faq...uminium-grilles

that 5k should cover main door and all windows easily, exclude balcony multi doors

Technically its my main door grille for apartment.. too poor to afford landed it is still in pristine condition, only thing that happened it collected dust only.

Powder coat when done correctly is one of the best coating coz its electrostatically applied.  Its used in lot of commercial appliances/lab machine outer boxes too.

Can ref https://www.thomasnet.com/articles/custom-m...powder-coating/

Whether you need a grille vs security door.. that depends on the level of ghettoness/Not-For-Human-Live-One index of your house