Document 0r64MYVY3rRMMGezpBaqw2ZM

'LWflWWJiUi LIA23006 - .S ok i e 'I*' A * . 'f* ^'r LEAD INDUSTRIES ASSOCIATION 4J0 LSttNOTON AVCNUC MCW YORK 17, N. Y. T" -* fiA * r-a '4 JhjrL W56 % SUBJECT, PA1WT *ULTAHTZED SURFACES?" REPRTKT 3 3 2 .3 ' To Mentor* of the Lead Industrie* Association, Attached 1* a copy of an article dealing with the painting of galvan ised surface* and incorporating caterial developed tgr the Aed Lead Technical Coccittee of the Pigaents and Chenieals Division of the Association. The article is reprinted frca the April, 1956 Issue of Tactarjr Management And 9 Maintenance Additional eople* are available and we shall be glad to supply then on request* lam a v,,*vae '.* 1 m^ftjrrvuv'-K1<m> HgH xmmsmmm $- L IA23007 wm* y % Paint Galvanized Surfaces? Some plant* do. Same don't; they're satisfied just to Irt galvanized roofs and sidings weather. But here are three good reasons to paint--plus a lot of how. ipw: * *' rT *,K" >" r*'W frts.n./ej surfers To ptutw. you ca * * ,c* m<v'lh` < *> HS m,IJ .Hf H nr.<r > is rhnrluit ot thionuic r>cTic<mcnl. lotlo.nl b> a n kind ol |wioL rrriIMC PAINT oa plvisiitd steel surfaces is a cornmoo head ache to maintenance men. Roofs and sidings to affected not only arc unsightly, but also pa to pot mote quickly. Why do these surfaces peel? Is there any way to avoid it? Why bother to paint a galvanized surface at all? Let's dispose of this last question first: tl really isn't necessary to paint the galvanized eatcfiors of ordinary plant buildings for protective pur poses v hen new. Nor even after tbc span clean appearance is dulled by 6 months' weathering. This weath ering ts normal, acts funher as a protective film for the rest of the life of the galvanized coaling. One authority says hare zinc coalings of 2 ounces per square foot of surface will Last 14 to 31 years in urban at mospheres. and 40 to tiO years ia purer country air. Three big why's--There are three nuin reasons for painting galvanized surfaces: ... F'xappraanct--A weathered surface admittedly is not attractor, and may mar the appearance of an otherwise wed-painted plant. And :f the plant pursues a definite color scheme, the need lor painting h ubs io u s . On the other hand, trans mission towers for utility power hncs--which are usually galvanized --are rarely painted. ... f or protection--Sometimes sesctc atmospheric conditions justify a protective civat of paint, even for transmissHsn towerv Such conditionv w:tl evict mostly in plant mIciiorv or in the vicinity of pro-e.s plants that make the kveal ail highly corrosive. You may avk: Why galvanize at all if you re going to add a proteclive coating' A newer: It multipart the protection. Under equal conditisvni a galvanized covering usi ally OiMrthwlW hr UAO INOUSTtltS ASSOCIATION. 410 W.livflM Avasvsra, Ntw Tart 17. N T. WP W" ~THrniyga.'WAi WBI i N 1985.01 mm I'm i ^ - Jf,:1 ... . x:: ;- .' ' ' ' ' - ' :- J wmwwnnM u p * i w >i * > ' - '' ' ;' .it&m ; .: rrfmimt'' rmii i>iwy.yM. ttfii .iri jive* longer nnt-ttsistant prolection o itccl than a normjt coal of paint. But i coal of paint added over gal vanized teel wiB greatly increate the protection. Here'* another kind of paint pro tection that'* needed. Galvanized turfacet thould be painted (when new) whenever there'* a threat of galvanic corrotion. Thi* can occur wherever turfacet overlap or come in contact with supporting Heel framework. Sometime*, as in the cate of bolt* or straps, such turfacet are kept apart by dielectric washer* or insulating gasket*. ,.. For ttplrrp--Thi* could be the cate of ac unpainted galvanized roof or tiding--or even a transmis sion tower--that had reached the point in year* of service where a coat of paint would save it for con tinued useful service. Ukt Joe* paial peel? One reason only--on any kind of surface: lack of adhesion. Adhesion is obtained Hi two ways: by molecular attrac tion to the metal, and by mechanical anchor. Chief culprit to destroying the bond is moisture. It's the same with painted gal vanized surfaces. W.ihout special measures of surface preparation, moisture and air (oxygen and car bon dioxidel will penetrate the coat of paint to the galsanized surface. Here llie moisture will react chemi cally with the zinc to produce the normal products of corrosion, such as zinc oxides and carbonates. This also describes ihe weathering process on bare palsani/cd unlaces But when coated with paint, the zinc oiides and carbonates combine with the fatty acids ra the paint oils. Result is a chemical soap film that loosens the paint bond This re action progressively weakens the zme coating So instead of protect ing the surface, the paint hastens it* destruction. How In awid pcrEag--All de pends whether you hair to paint new or old galvanized turfacet. Two method* of painting are possible. In one, the galsanized surface it al lowed to weather for three to til months before painting. This work* fairly well as far at pood paint ad hesion it concerned. Nobody teem* to know for sure why paint will stiek after weathering Beat answer it that wrjlhrnrg provide* enough me chanical adhesion to counterbalance Ihe bad effects of any oxide or car bonate tccclion that may occur. But there'* a question as to whether the maximum life of surface protection it obtained thi* way. AHo, painting the structure later usually involve* higher cost* because the surface mutt be cleaned. And sometimes cost of rigging and covering is greater once the plant it operating. The second method call* for sperfal pre-treatment of the new gal vanized surface to improve it* adhesive qualities. Traditional ways have been to etch it with a mild acid, such as hydrochloric acid in toluol and alcohol, or soak it with solu tions of acetic acid, nitric acid, sal soda, and similar chemicals. How well have any of these etch ing pre-treatments worked? There arc various shades of opinion--none too glowing. According to a leading authority, the Steel Structures Paint ing Council, results have been only fair at best. In fact, the Council claims that sometimes the treat ments have destroyed the zinc coat ing altogether, thus accelerated the corrosion of the structure. In gen eral, most every one agrees there has never been complete satisfaction with the acid-washing technique. Realizing this fact, LIA. (Lead Industries Association) desoted two years to study it. What was needed, i! concluded, were both an ctleclive method of pre-treatment and a new kind of paint. As a result of its research and tests, it has recently announced a series of fist new paint formulations lo suit the various prob lems of application. These formula tions--LIA. 9-1 to 9*5--can be made up by any competent paint CORROSION'. llmkfMtk of roof of areborn* khoi ho* (***1) app4trd flM dhla'l Mop dCIfftCMttHML manufacturer. They all .' lude red w lead at a pigment because c ' rust inhibiting properties. In brief, here's how to use them on either old or new surfaces; UA. 9-1--for single coat cut sheds or buildinp where protection is important, appearance secondary. Has i linseed oil-alkyd vehicle, well suited for rusty surfaces because of its wetting quahtk-. UA. 9-2--for a single coat Job, similar to No. I, but using a faster drying straight alkyd vehicle. Good for new, pre-treated surfacei\ UA. 9-}--similar to No. 1, but with green tint, UA. 9-4--for use ag^prlmary coat to be followed by a top coal. Same vehicle as No. I. UA. P-5--Similar to No. 4, ex cept same vehicle as No. 2. These new developments m paints do not eliminate the need for proireatment of new galvanized sur faces. But several authorities rec ommend a pre-treatment with a phosphate or chromate preparation, rather than by the dubious "etch ing" procedure. The Steel Struc tures Painting Council suggests nooflammablz liquid zinc phosphate, ap plied by brushing, spraying, or in an industrial washer. In section 6.7 of its Specification MIL-Z-1787) the U S. Navy says phosphate or chro mate treatment will extend the life of zinc-coated articles, provide an excellent pre-treatment for painting Ihe t.I.V claims that treatments with copper sulphate, acetic acid, or hydrochloric acid arc ineffective im nea galsanized steel surfaces. But phosphate cleaning prevents the chemical reaction with fatty acids in paint oils by coating the galvanized surface with a fine, crystalline layer of inert zinc phosphate. If salts arc formed, they don't come in contact with paint oils. LIA. further states nut pnosphate treatments effectively roughen the zinc surface, improve adhesion. Stdpi in pre-treatment, UA. points out. are simple: ... Own sur/orr--Remove ad grease. Scrub lightly with steel woe] lo expose true metal surface. .Apply H'luti.m -- Bruxh or spray uniformly on cleaned surface. A protective coating will form in one to two minutes. . .. Hash ihe civlint with cold water, with sponge, rag or hose. Al low to dry. kvpesntvd from FACTORY MANAGEMENT AND MAINTENANCE AFRIL, im 9en;si. its*. u ,c ,.. h .i z.xr.*.M c. ic. IM Wni IU li. H*. Ywi It M. t. 9 0 m Jtmi-.awu.gj.tyi,.I I I.ii.ingppg^jymm ~ ;-;*r