The protective qualities of the iron phosphate protective coating which is the by-product of phosphoric acid based iron cleaning fluids are discussed, as are vapour phase inhibitors. The tests were carried out on six pieces of wrought iron cut from one well-weathered bar covered with flaky corrosion products and layers of paint. The pieces were all cleaned with a phosphoric acid cleaner; (1) was then bright cleaned and left uncoated, (2) was bright cleaned and immersed in hot paraffin wax (3) was bright cleaned and coated with polyvinyl acetate in toluene, (4) had the iron phosphate coating left on, (5) was oven dried and coated with polyvinyl acetate solution. In the first test they were exposed to damp, dirt, splashes and temperature changes, in the second to very high humidity. The results showed the necessity of thorough drying, that polyvinyl acetate is effective under dry conditions but not with high humidity, that wax gathers dirt but is not so liable to fracture of the coating. The iron phosphate coated bar showed no corrosion even in high humidity; the disadvantage is its poor and patchy colour but it can be dyed black with an aqueous solution of Hematine crystals. Tests were also made with vapour phase inhibit-ors, the most suitable being cyclohexylamine-carbonate. Shell Nos. 220, 250, and 260 were tested and no corrosion occurred on the bar protected with Shell 220 after one year. It must not be used with lead and copper as they are liable to be attacked by the vapour.