can we paint on galvanised sheet?
Answers:
hiya zam...
painting galvanized can be a little tricky, but it is paintable. new galvanized is often oily and should be wiped down with solvent (lacquer thinner, naptha, mineral spirits)...some manufacturers will then recommend a mild acid wash (vinegar & water solution) prior to painting for these reasons - (a) galvanized metal is very alkaline - the acid wash (pickling) will somewhat neutralize the surface and make it a little closer to ph balance, and (b) because galvanized is metal and vinegar is acid, the mild acid wash will microscopically "profile" the slick surface of galvanized metal to allow better tooth for a mechanical bond between primer and substrate...
DO NOT SAND GALVANIZED PRIOR TO PAINTING - the galvanic process is sacrificing a non-ferrous metal (zinc) to protect a ferrous metal (steel)...by sanding the galvanized surface, you score through the zinc protection and expose the ferrous metal to oxidation (rusting will occur)...
there are many types of appropriate galvanized metal primers on the market. DO NOT USE A FERROUS METAL PRIMER. ferrous metal primers are usually an alkyd (oil-based) and alkyd products are never recommended for alkaline surfaces (peeling will occur)...galvanized primers may be solvnet thinned - or require a solvent to clean-up with - but they are not conventional oil-based products and contain no alkyds.
many galvanized metal primers are water-borne acrylics(sometimes referred to as latex) - they thin and clean-up with soap and water and still provide excellent adhesion and protection to galvanized surfaces...and for residential use, many paint manufacturers recommend just painting with a high quality acrylic paint and not to use a primer at all.
if the galvanized is aged...you'll want to treat it a little different than new galvanized. contrary to popular opinion, galvanized metal will rust. however, the rusting that occurs on zinc is not like that of ferrous metals. the "rusting" or oxidation appears as a white, chalky film and does not attack the host as oxidation of ferrous metals do. but this oxidation film must be addressed prior to painting or priming. to remove this film, scrub surface with a sudsy detergent solution of 1 cup tri-sodium phosphate to 1 gallon of warm water - rinse with clean water then "pickle" the surface with a vinegar and water solution (1 part vinegar to 1 part water)...after surface has dried, then apply appropriate primer or finish coat as directed by the instructions on the product label.
for more detailed info on painting galvanized, contact your local independent paint store...big boxes like home depot and lowes may have the products you need, but rarely do they have the experienced personnel that can walk you through a tricky situation...
i hope this info is helpful, feel free to e-mail me if you have other questions.
ric
Other answers:
yes, apply primer first
yes, apply primer first
Galvanized can be hard. Sand lightly & prime it.
Yes but you must first prime it with a metal primer. Ant hardware store should have a product you can use.
yes, but they are still danged uncomfortable to sleep on.
yes wipe with an acid like vinegar then if primered with a shellac primer it will accept any paint,, you can also use a ferrous primer,,, i dont know the specific use ,so i cant tell you the finish paint to use ,contact a dealer like ici dulux glidden ,,ive sold their paint and applied it for 16 years,, and painted since 1980,,, an olde dude