Document zdvewE2j23R3yX6252Lb1oNB

E. I. DU PONT DE NEMOURS & COMPANY KREBS PIGMENTS DEPARTMENT 256 VANDERPOOL STREET NEWARK. NEW JERSEY Serial No.-vs^ Copy No. / K2-44~64 /t/V - Period Covered: NEWARK PLANT PIGMENT COLOR RESEARCH REPORT Final Report Blistei*ing & leastlag of Paint Films on Continuous lamerslon June 1943 - Calebsr 1944 FILE: DATE: 343.5 11-19-44 N37935 6^ Copy to: #1 - Numerical File - Research Office - library File -.laboratory : Extra Serial No. 0-44-66 Copy No. / NEWARK PLANT PIGMENT COLOR RESEARCH REPORT Final Report Title: Blistering & Rusting of Paint Films on Continuous Immersion Period Covered: June 1943 - October 1944 ."f*. SUBMITTED BY: E. Hoskin APPROVED BY: DATE SUBMITTED: 10/31/44 DATE ISSUED: 11-15-44 DUP050149706 -2- immrau The original purpose of this study was to develop addition al information on blistering which might be useful in designing ?v future tests. Unfortunately, it was impossible to follow the tests closely except in the early stages and most of the paints remained in water.,, for 456 days before they were finally examined. At this time, blistering was severe in*all cases and there was not much difference between them. Their final condition is reported simply to complete the record. #* reviUs work (staffer example I5HH3-164) that topeoated and untopcoated panels behived differently in respect to blistering on imaereton. Therefore in this seriis duplicate panels of each type were Exposed. As a possible means of aimpnfyaag future tests, it was decided to expose panels topeoated on one side only. 5 fi f/ Sif Two vehicles were used viz. KV-15 and KV-26. The pigment systems are listed in Table I. SUMMARY ARP CQMCLUSIQHSt Specifically, the work was carried out with the following objectives. 1. To determine the relative behavior of sine yellow, "Impedex#, iron oxide, and asbestine when used as a single pigment or in combination in a primer film when exposed to the distilled water lamersion test. 2. To compare the behavior of topeoated and untopcoated primer films when exposed to the distilled water immersion test. 3. To determine the possibility of using a single panej., one side of which is topeoated, the other of which is Untopcoated, instead of using two panels both aHlls of which are alike, either topeoated or untopcoated. Comparison of the behavior of the various pigments in primer films is based (1) on the time required for the films to show blistering or rusting, and (2) on the rusting of the metal under the film after long immersion. The conclusions which follow are based primarily on the behavior of untopcoated primers because the use of a topcoat obliterated most of the differences in perform ance obtained between the primers (see chart). Some of the results obtained do not check those from earlier experiments (cf. 6749) and any conclusions drawn in these casef^orrespondingly uncertain. 1. Phenol!c/alkyd (KV-26) primers of 0/100, 50/50, and 100/0 per cent nImpedexw/zinc yellow showed that nImpedexn lengthened the time elapsed before the untopcoated film failed by blistering. The improvement was roughly in proportion to the amount of "Impedexn used. This tendency was also indicated by the corresponding DU PQ50149707 3 X?*15 primer. The loss of yellow dolor which occurred along with blistering increased in proportion to the amount of "Impede*" used* 2, final observation of me abort panels after 456 days Immersion re vealed the tendency of "Impedes:* to improve the adhesion of the primer film to the metal surface, but at the seme time to decrease the tendency of sine yellow to prevent sub-film corrosion, 3. Final observation of the above panels also led to the conclusion I that topcoat adhesion to the primer vas improved when the sine yellow/*p%edex* ratio was large. 4* Phenolic/alkyd (KV-26) primers of 0/100, 50/50, and 100/0 -- "Impedex/Asbestine showed that "Xsipedex" lengthened the time elapsed before the untcpcoated film failed by blistering roughly in proportion to the amount of "Impedes* used, the final con dition of the panels was also better when impedes* was present. 5. Bed Lead in R.L.0. gave a very good performance. 6. The extent of blistering after 456 days immersion was bad for all panels. The size of the blisters varied on the individual panel : from large to small, the number of smaller ones increasing in the ease of sine yellow and asbestine primers with increasing amounts of "lapedex". The loop "Impede** primers had the finest size blisters. Correlation between size of blisters and primer adhesion for these paints was also observed, the finer the blisters the better the primer adhesion. 7. The "Impede**/zinc yellow -- 50/50 primer was superior to the "Impedex"/iron oxide -- 50/50 primer in life of the film and protection of the panel against rust. 8. In general, results (resistance of the film to early blistering and rusting and protection of the panel against rust on long Immersion) obtained with separate panels agreed with the results obtained using single panels, one side topeoated, the other side untopeoated. However, it is doubtful whether single panels are practical for general use in immersion testing, as very often the length of time necessary to obtain the desired results differs for topeoated panels from the length of time required for untopeoated panels. 9* All topeoated panels showed early and about equal signs of failure by blistering. The one and two coat panels of the Havy Hark Gray topcoat were about alike in film life end final con 1 dition* The final condition of the panels after 456 days immersion varied In protection of the metal against rust, top coat adhesion, and kind of blistering according to the primer used. DUP050149708 10* An unpigoeated K7-26 flla was found to give excellent protect ion* the KV-15 film (unplgmented) was very poor. ' Pigment Yolume - 40$ Vehicle - KV-15 -- 50/50 m Beryl B69-1 (solids)/R.L.O. KY-26 --- 65/35 phenolic spar varnish/GB-2466 (The spar varnish * 25 gal* oil length BR-254 50/50 tung*/L*0# vehicle) R.L.O. -- Bed lead primer only Means of Grinding - Ball mill Table I lists the systems which were investigated and shows both their behavior in the early stages of the test and the condition after 456 days immersion in distilled' water* Sub film rusting was evaluated by stripping the paint from the panel* She chart shows in graphic form the time required for blistering to develop* Blistering after 456 days was graded by the system now in use by the Paint Laboratory rather than by the Aim method* The *Xw*s represent the area covered by blisters; X * very small area, XXXXXX entire area. 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