Document YDqgVeQKzJ7aDyDV7GjzZ9Mxn

Cross Reference: National Lead Company Inhibitlve Pigments PigmentA Dept 0 CC: Mr, Jo Bo Bullittj,. Labo v Mr, Jo Wo 1.11 ff, Lab, Mr, Co R, IS* Merkle, Labo Mr. Stuart Graves, tab. Dr. R, B, Davis, flint , IB MABS1LL LIBOilOl! L1BRABY Philadelphia Laboratory July 11, 1949 MEMORANDUM REPORT NO. M-25$: WfNDBCED' ?*. > *% ft II0i 30*5$ BARIUM CHROMATE PIGMENTS NATIONAL LEAD COMPANY*S "PIGMENT S" The National Lead Company is currently promoting a barium and potassium chromate pigment called ''Pigment En, "Pigment B" and a barium chromate pigment supplied by the Pigments Department have been evaluated by the laboratory, "Pigment B" is very slightly better than zinc yellow in a high spot test over rusted structural steel but is not as good as red lead. Exposures over dean steel have not matured yet. Barium chromate pigment does not show improvement over the red lead controls when rusted auto body steel is the substrate but will be tried against our present zinc yellow controls over rusted structural steel when it can be fitted into a metal protect-* ive series. Sulfate ions have been found present on samples of rust taken from all of our exposure stations. Barium sulfate is insol uble and some work has been done to find pigments (other than red lead) which precipitate sulfate. However, barium chromate is also quite insoluble and removes Sulfate ions from solution very slowly. "Pigment E% on the other hand, has so much chromate ion solubility from the potassium chromate that it will release sulfate ions from blano fixe by mass action. Therefore, it Cannot act as a sulfate precipitator. Details: A talk on "Pigment R" was given at the April meeting of the Paint and Varnish Production Club by A. J. Siekhoff of the National Lead Company, The talk appears in the April issue of the Official Digest, "Pigment E" is Shown to be the double salt BaKg Tcr204Ti by X-ray diffraction analysis. However, they report that "Pigment E" when leached successively with water, forms a solution of potassium chromate and leaves a residue of barium chromate. They don't explain how the fact that it is a true double salt is relevant to the subject of metal protection when it breaks down so readily bn contact; with water and it depends on this breaking down for the lnhibitive action which is claimed* The first washing has been found tq contain no barium in our work at the Philadelphia Laboratory although a half-normal solution of chromate is quickly extracted from the pigment or about six times as much as IS readily available with zinc yellow* The pigment is not made from the chlo ride salts but we find it contains considerable soluble chloride* Data.on controls were not shown for exposures, tensile strength, elongation or hardness, A control was shown for salt spray teats on automotive primers, but the soluble chromate pigments are at their best in salt spray where osmotic pressure outside the film is great. Data obtained on our Delaware fence are listed in the attached table,, In putting out our exposures on sulfate precipitation, a barium chromate salt was originally scheduled even though it had been tested in the past but was left out when it failed a sulfate precipitation test in which excess barium chromate in a Fe(SO4)3 solution was shaken and allowed tp stand overnight* Before dis carding the solution several months later, a test showed that sul fate was no longer present* Barium Chromate will not precipitate sulfate as fast as will the stearate, carbonate, nitro-phthalate of lead pigment a* Barium obromate will probably prevent the pene tration of sulfates through the film hut probably does not have quite enough solubility to precipitate sulfates in the rust when added as a pigment* Nevertheless, in view of the recent finding that it will precipitate sulfate although slowly, it should be given a fair try and will be put in the next series. The solu bilities of barium chromate and sulfate {blanc fixe, barytes) are 0*00034 and 0,00018 grams per 100 co respectively. The presence of chlorides on the barium ohromateS in the previous work is not known and may have masked the good qualities which we might expect from the pigment as a aulfate precipitator. Chlorides were more than likely present in the iron oxide contain ing primer* ^n insufficient amount of chromate in the presence of chlorides is reported (0* Evans, ''Metallic Corrosion & Passivity" 1937, P-299) to concentrate the electrolytic attack bn small areas forming deep pits. In the presence of excess aoids, chromates do not inhibit corrosion and may actually stimulate it by acting as a depolarizer for hydrogen* The pH of zinc yellow is 6*3,"Pigment E" is 6,2 and Barium chromate is 6,8, On rusted auto body steel, barium chromate is good in raw oil or when supplemented by iron oxide in alkyd but alone in alkyd it fails rapidly, Results of Series 3534 and 3749 are listed in the attached table* PHILADELPHIA LABORATORY WG4 :ms ATTACH; WILLIAM C, JOHNSON DUP030003133 A.S.T,-M R a tin g s a t 3 M onths (P e l R usted CJiannel Ir o n 9 . \. 5 6 .R usted Sheet G lean B o ile rp la te a sr NO n O\n n O 03 t 3 + foit a o Hin^ *ri (!) *4 <6 U >> vO aao vO 0n O0 E-< * 33o a! a H SfrC'-Or'MCNV t<-8t rt n >4 !>> Xt H l* < W*<'O _a <! <H jrHrt'5(30 'O O CB rat4 OS o| H t) 3 P O J3 a 13 03 40 a a0 NO _g T1 IN C>* H On <0 M h IN fv CO cdvcvora H 03 t lrA4 H CHV iWrl H t~\ + t-< fc< r*4 a f7 a ta o is OM-tVO.HNO r-(NO~4 <SiC^'PPl-CN*'>OCN- a H $ * W 4 $3 & &: rd + ++ +++ nOOOnOuUnNn OOnOoOvO o JO o !0 p > Si M < <a xt in !> .8 id id H a< < "O rf Wvrl O CJ id .snj*i xt 0 SM o <o a id1 H O r-j *C <5 H MM H o* *4 0*0hfl 35 is Sid p o *"( o drl N rl a r-t I 0& J ttiS W H 0 {H CO'O "Sf Ns>-t aH o IHNPH- 12 0* a s 8 op * a r*l vpO-ovO N On F\ IN 03 nJ4 i. 46 Alfcyd 67=7 eSdemiin t w u o it Y ell ubst e s S in tE Rea Lead i n O il 7=746 igm en P rim er 6 P DUP030003134