Paint Technology and Tests Part 24

"On Wednesday, June 28, 1911, the second inspection of the Atlantic City Steel Test Panels, erected in October, 1908, was made by Sub-committee D of Committee D-1, this Committee having agreed to report upon the condition of the painted surfaces, leaving any report on the comparative corrosion of the various types of metal used in the test to Committee A-5 on the corrosion of iron.

===+=========================+=======+=======+======+=======+========= | | | | | |Grams | | | | | |Paint | | |Wt. of | Sp. |Wt. of |to Panel | Name | Sp. |Pigment| Gr. | Paint |at 900 | | Gr. |to Gal.| of | per |Sq. ft.

Pigment |of Pig-|of oil |Paint | Gal. |spreading No.| | ment | Lbs. |Rec'd | Lbs. |rate ---+-------------------------+-------+-------+------+-------+--------- 1|Dutch process white lead | 6.83 | 20.49 | 2.45 | 20.49 | 61.0 2|Quick process white lead | 6.78 | 20.34 | 2.47 | 20.34 | 62.0 3|Zinc oxide | 5.56 | 16.68 | 2.12 | 16.68 | 59.0 4|Sublimed white lead | 6.45 | 19.17 | 2.36 | 19.17 | 59.0 5|Sublimed blue lead | 6.39 | 19.17 | 2.42 | 19.17 | 61.0 6|Lithopone | 4.26 | 12.78 | 1.80 | 12.78 | 45.3 7|Zinc lead white | 4.42 | 13.26 | 1.96 | 13.26 | 49.4 9|American orange mineral | 8.97 | 26.91 | 2.97 | 26.91 | 74.7 10|Red lead | 8.70 | 26.10 | 2.93 | 26.10 | 73.6 12|Bright red oxide | 5.26 | 15.78 | 2.05 | 15.78 | 60.0 14|Venetian red | 3.1 | 9.30 | 1.52 | 9.30 | 38.0 15|Prince's metallic brown | 3.17 | 9.51 | 1.50 | 9.51 | 37.7 16|Natural graphite | 2.60 | 7.80 | 1.37 | 7.80 | 34.4 17|Acheson graphite | 2.21 | 6.63 | 1.22 | 6.63 | 30.8 19| {Lampblack | | 1.82}| | 1.82 | | {Barytes | 1.82 | 8.92}| 1.60 | 8.92 | 40.2 20|Willow charcoal | 1.49 | 4.47 | 1.08 | 4.47 | 27.0 21| {Gas carbon black | 1.85 | 1.39}| 1.67 | 1.39 | | {Natural barytes | | 10.03}| | 10.03 | 50.7 24|French yellow ochre | 2.94 | 8.82 | 1.46 | 8.82 | 37.0 27|Natural barytes | 4.46 | 13.38 | 1.83 | 13.38 | 46.0 28|Precipitated barytes | 4.23 | 12.69 | 1.84 | 12.69 | 46.0 |(blanc fixe) | | | | | 29|Calcium carbonate | 5.48 | 8.22 | 1.37 | 8.22 | 34.5 |(whiting) | | | | | 30|Calcium carbonate | 2.56 | 7.68 | 1.35 | 7.68 | 34.0 |precipitated | | | | | 31|Calcium sulphate (gypsum)| 2.33 | 6.99 | 1.25 | 6.99 | 31.4 32|China clay (kaolin) | 2.67 | 8.01 | 1.34 | 8.01 | 34.0 33|Asbestine (silicate of | 2.75 | 8.25 | 1.38 | 8.25 | 34.7 |magnesium) | | | | | 34|American vermilion | 6.83 | 20.49 | | 20.49 | 64.5 |(chrome scarlet) | | | | | 36|Medium chrome yellow | 5.88 | 17.64 | | 17.64 | 67.1 39|Zinc chromate | 3.57 | 10.71 | 1.57 | 10.71 | 39.2 40|Zinc and barium chromate | 3.45 | 10.35 | 1.58 | 10.35 | 40.0 41|Chrome green (blue tone) | 4.44 | 13.32 | 1.94 | 13.32 | 49.0 44|Prussian blue | 1.96 | 5.88 | | 5.88 | 30.0 45|Prussian blue | 1.93 | 5.79 | | 5.79 | 34.5 48|Ultramarine blue | 2.40 | 7.20 | 1.29 | 7.20 | 32.5 49|Zinc and lead chromate | 4.76 | 14.28 | 1.92 | 14.28 | 48.3 51|Magnetic black oxide | | 15.00 | 1.92 | 15 | 48.3 | | | | | | | _Composite Paints_ | | | | | | | | | | | 111|Brown } Made from pig- | | 10.82 | 1.30 | 10.82 | 32.7 222|Black } ments that were | | 10.86 | 1.30 | 10.86 | 32.8 333|White } inhibitive in the| | 14.52 | 1.74 | 14.52 | 43.8 444|Green } water test | | 12.77 | 1.53 | 12.77 | 38.6 | | | | | | 555|Black } Made from pig- | | 9.37 | 1.125| 9.37 | 28.

666|Brown } ments that were | | 11.74 | 1.41 | 11.74 | 35.5 777|White } stimulative in | | 14.55 | 1.75 | 14.55 | 44.

888|Green } the water test | | 14.57 | 1.75 | 14.57 | 14.57 ===+=========================+=======+=======+======+=======+=========

"According to the amount of rust apparent on the painted surfaces of the panels, as well as the degree of checking, chalking, scaling, cracking, peeling, loss of color, and other signs of paint failure shown, ratings were given each panel. The system of rating which took into consideration all the above conditions, was similar to the system used at the first inspection during 1910, when 0 (zero) recorded the worst results and 10 (ten) the best results.

"In Table No. 1 there is shown the rating accorded by each inspector to each panel, as well as an average for each panel.

TABLE NO. 1.--SECOND INSPECTION OF STEEL PAINT TEST PANELS AT ATLANTIC CITY, N. J., BY SUB-COMMITTEE D OF COMMITTEE D-1

=======+========================+======+======+=======+=======+======= | | | | H. A. | | Panel | |W. H. |P. H. |Gardner| C. | No. | Pigment |Walker|Walker|Chair- |Chapman|Average | | | | man | | -------+------------------------+------+------+-------+-------+------- 1 |Dutch process white lead| 2 | 3 | 3 | 5 | 3.7 2 |Quick process white lead| 4 | 4 | 3 | 6 | 4.2 3 |Zinc oxide (XX) | 1 | 1-1/2| 1 | 2-1/2| 1.5 4 |Sublimed white lead | 9 | 9-1/2| 9 | 8-1/2| 9.0 5 |Sublimed blue lead | 9 | 9-1/2| 9-1/2| 7-1/2| 8.8 6 |Lithopone | 2 | 1-1/2| 2 | 3-1/2| 2.2 7 |Zinc lead white | 3 | 4 | 5 | 7 | 4.7 9 |Orange mineral | 9 | 9 | 9 | 6-1/2| 8.3 10 |Red lead | 9 | 9 | 9 | 6-1/2| 8.3 12 |Bright red oxide | 8-1/2| 9 | 8 | 7 | 8.1 14 |Venetian red | 7 | 9 | 7 | 9 | 8.0 15 |Prince's metallic brown | 5 | 7-1/2| 6 | 8 | 6.3 16 |Natural graphite | 6 | 8 | 4 | 9-1/2| 6.8 17 |Artificial graphite | 5 | 7-1/2| 4 | 7 | 5.9 19 |Lampblack | 5 | 7-1/2| 5 | 8 | 6.3 20 |Willow charcoal | 9 | 8-1/2| 9 | 9 | 8.8 21 |Carbon black | 7 | 8-1/2| 5 | 8-1/2| 7.2 24 |Yellow ochre (French) | 5 | 7 | 2 | 8 | 5.5 27 |Barytes (natural) | 1 | 1 | 1 | 0 | 0.7 28 |Barytes (precipitated) | 2 | 1-1/2| 2 | 2 | 1.8 29 |Calcium carbonate | 0 | 0 | 0 | 0 | 0.0 |(whiting) | | | | | 30 |Calcium carbonate (pre- | 0 | 0 | 0 | 0 | 0.0 |cipitated) | | | | | 31 |Calcium sulphate | 1 | 1 | 1 | 3 | 1.7 |(gypsum) | | | | | 32 |China clay (kaolin) | 6 | 6 | 7 | 6-1/2| 6.3 33 |Asbestine (magnes. sili-| 5 | 4-1/2| 6 | 5 | 5.1 |cate) | | | | | 34 |American vermilion |10 |10 | 10 | 10 | 10.0 36 |Lead chromate | 7 | 7-1/2| 8-1/2| 8 | 7.7 39 |Zinc chromate | 9 | 9 | 10 | 9-1/2| 9.5 40 |Zinc and barium chromate| 9 | 9-1/2| 10 | 9-1/2| 9.5 41 |Chrome green (blue tone)|10 |10 | 10 | 9-1/2| 9.8 44 |Prussian blue, W. S | 9 | 9-1/2| 9-1/2| 9 | 9.0 45 |Prussian blue, W. I | 8 | 9-1/2| 8-1/2| 8-1/2| 8.5 48 |Ultramarine blue | 0 | 0 | 0 | 0 | 0.0 49 |Zinc and lead chromate |10 | 9-1/2| 10 | 9-1/2| 9.7 51 |Magnetic black oxide | 9 | 9-1/2| 10 | 9-1/2| 9.5 111 |Brown composite paint | 7 | 9 | 9 | 9 | 8.5 222 |Black composite paint | 9 | 9 | 9 | 8-1/2| 8.8 3333 |White composite paint | 4 | 4 | 7 | 3 | 4.5 444 |Green composite paint | 5 | 7 | 7 | 8 | 6.7 555 |Black composite paint | 9 | 9 | 6 | 9 | 8.2 666 |Brown composite paint | 8 | 8 | 6 | 9 | 7.7 777 |White composite paint | 7 |10 | 5 | 7 | 7.2 888 |Green composite paint | 7 | 8 | 8 | 9 | 8.0 2000 |1 coat zinc chromate }| 8 | 8-1/2| 8 | 8 | 8.1 |1 coat iron oxide ex- }| | | | | |cluder }| | | | | 3000 |1 coat lead chromate | 7 | 8 | 7 | 7-1/2| 7.3 4000 |1 coat red lead }| 7 | 8-1/2| 8 | 7-1/2| 7.7 |1 coat iron oxide ex- }| | | | | |cluder }| | | | | 100 |Straight carbon black | 5 | 8-1/2| 4 | 8-1/2| 6.5 |paint with turps and | | | | | |drier | | | | | 90 |Straight lampblack paint| 5 | 7 | 3 | 8 | 5.7 |with turps and drier | | | | | 5555 |Coal tar paint over red | 4 | 8 | 2 | 7 | 5.2 |lead | | | | | 1000 |Chrome resinate in oil | 1 | 0 | 0 | 2 | 0.7 |(1 coat) | | | | | 1 plate|3 coats boiled linseed | 1 | 0 | 1 | 4 | 1.5 |oil | | | | | =======+========================+======+======+=======+=======+=======

"In Table No. 2 there is shown the rating obtained by those panels which were considered by the committee as meriting from 8 to 10, and having given the best all-round service.

TABLE NO. 2.--a.n.a.lYSIS OF AVERAGES. GRADE OF EXCELLENCE FROM 8 TO 10

=====+=============================================+======= Plate| Pigment |Average -----+---------------------------------------------+------- 34 | American vermilion (basic chromate of lead) | 10.0 41 | Chrome green | 9.8 49 | Lead and zinc chromate | 9.7 39 | Zinc chromate | 9.5 40 | Zinc and barium chromate | 9.5 51 | Black oxide of iron | 9.5 4 | Sublimed white lead | 9.0 44 | Prussian blue | 9.0 5 | Sublimed blue lead | 8.8 20 | Willow charcoal | 8.8 222 | Composite paint | 8.8 45 | Prussian blue | 8.5 111 | Composite formula | 8.5 9 | Orange mineral | 8.3 10 | Red lead | 8.3 555 | Composite paint | 8.2 12 | Bright red oxide of iron | 8.1 2000 | 1 coat zinc chromate; 1 coat iron oxide | 8.1 14 | Venetian red | 8.0 888 | Composite paint | 8.0 =====+=============================================+=======

=Comparison of Results.= It is of interest to compare with Table 2 of the above report, Table 2 of the 1910 report of Committee U of the American Society for Testing Materials. Both charts show the highly inhibitive pigments to be in the lead.

COMMITTEE U REPORT 1910

TABLE II.--a.n.a.lYSIS OF AVERAGES. GRADE OF EXCELLENCE FROM 8 TO 10

(_Only resistance to corrosion was considered, and only pigments which were common to both tests are included_)

===+====================================+======= No.| Pigment |Average ---+------------------------------------+------- 34 | American vermilion (chrome scarlet)| 9.8 41 | Chrome green (blue tone) | 9.7 40 | Zinc and barium chromate | 9.7 5 | Sublimed blue lead | 9.6 4 | Sublimed white lead | 9.5 49 | Zinc and lead chromate | 9.5 39 | Zinc chromate | 9.4 12 | Bright red oxide | 9.3 44 | Prussian blue (water stimulative) | 9.2 16 | Natural graphite | 9.1 9 | Orange mineral (American) | 9.0 36 | Medium chrome yellow | 9.0 2 | White lead (quick process) | 8.9 20 | Willow charcoal | 8.8 45 | Prussian blue (water inhibitive) | 8.8 1 | White lead (Dutch process) | 8.7 10 | Red lead | 8.7 7 | Zinc lead white | 8.0 ===+====================================+=======

The writer has recently made a careful inspection of the panels painted with single pigment paints, and has made the following brief summary of the characteristic appearance of each.

=Panel No. 1--Dutch Process White Lead.= The excessive chalking which took place began to disappear at the end of a year, being washed away by the rains and carried away by the winds, so that there was left upon the surface but a thin coating of pigment, insufficient to give good protection. Slight corrosion was apparent beneath the film.

=Panel No. 2--Quick Process White Lead.= In the same condition as Panel No. 1.

=Panel No. 3--Zinc Oxide.= Panel covered with thin lateral streaks of rust, due to the admittance of moisture in cracks caused by brittleness of film. Result doubtless due to insufficient amount of oil used with pigment. Removal of film shows steel very bright except where cracks have formed.

=Panel No. 4--Sublimed White Lead.= Although sublimed white lead chalked very heavily, the chalked pigment seemed to be tenacious and adhered to the plate, presenting an excellent surface with absence of rust. Film of good color and quite elastic.

=Panel No. 5--Sublimed Blue Lead.= In same condition as Panel No. 4, but color has slightly faded.

=Panel No. 6--Lithopones.= Lithopone was early destroyed, as is usual with this pigment when used alone on exterior surfaces. It became rough and discolored, presenting a very blotchy appearance and disclosed the formation of rust working through the film.

=Panel No. 7--Zinc Lead White.= In general good condition with the exception of the color, which is slightly dark. Medium chalking was apparent but only very slight corrosion appeared.

=Panel No. 9--Orange Mineral.= In excellent condition, showing a good firm surface with no checking or corrosion apparent. Shortly after exposure the film became covered with a white coating of carbonate of lead, which indicates action of the red lead with the carbonic acid of the atmosphere. Removal of this white coating with water discloses the brilliant color of the unaffected portion of the red lead.

=Panel No. 10--Red Lead.= In same condition as Panel No. 9.

=Panel No. 12--Bright Red Iron Oxide.= In general good condition. Film intact and unfading in color.

=Panel No. 14--Venetian Red.= Similar to Panel No. 12, but slight corrosion apparent beneath, in localized spots, and film showing slight wart-like formations.

=Panel No. 15--Prince's Metallic Brown.= Similar to Panel No. 14.

=Panel No. 16--Natural Graphite.= Deeply pitted in spots, showing bulbous eruptions, indicating the stimulative nature of this pigment.

=Panel No. 17--Artificial Graphite.= In same condition as Panel No. 16.

=Panel No. 19--Lampblack and Barytes.= Although the film seems to be intact, there are apparent abrasions of the surface showing stimulative corrosion effects of a p.r.o.nounced nature.

=Panel No. 21--Carbon Black and Barytes.= In same condition as Panel No.

19.

[Ill.u.s.tration: Corrosion Pits on Graphite Panel]

[Ill.u.s.tration: Rust on Stripped Graphite Film]

[Ill.u.s.tration: Section of Wire Painted with a Stimulative Carbonaceous Paint]

[Ill.u.s.tration: Corroded and Pitted Surface of Plate Painted with Stimulative Paint]

The longevity of lampblack and carbon black paint films when applied to wood has been attributed to the slow drying nature of these pigments when mixed with oil. It is a.s.sumed that they have the property of keeping the oil in a semi-drying condition, which will not disintegrate as early as when the oil is thoroughly dried to linoxyn. If this is true, it would seem advisable to use with hard-drying pigments, a proportion of some oil that is semi-drying in nature or one which will leave a film not too hard. Soya bean oil, wood oil, and fish oil present themselves as candidates for such use. How they will work in practice, however, is a question not yet determined. On the other hand, it is well known that these pigments require enormous quant.i.ties of oil in order to grind to a working consistency, and it is possible that the life of such coatings is due rather to the property of these pigments, of taking up large quant.i.ties of oil, than to their effect upon the slow drying of oil. Excessive oil carrying, however, should be avoided, as shown by the early failure and pitting of those carbon black and lampblack paints ground with very large quant.i.ties of oil, as is the usual practice. When these carbon and lampblack pigments were ground with barytes (which is a heavy pigment and requires only about 9 pounds of oil to 100 pounds of pigment, as against 175 pounds of oil to 100 pounds of lampblack), it was found that the lampblack and carbon black paints were reinforced and made more suitable for actual practice. The stimulative nature of these black pigments, however, a.s.serted itself in both cases, and large pittings and eruptions were evident at the end of a year. Carbon black, lampblack, graphite, or any other good conductor of electricity should never be placed next to the surface of iron. They are good as top-coatings, but not as prime-coaters. Some pigments are stimulators of corrosion, because they contain water-soluble impurities that hasten the rusting, while others, like graphite, hasten it simply because, being good conductors, they stimulate surface electrolysis.

=Panel No. 20--Willow Charcoal.= In excellent condition throughout.

Presence of small quant.i.ties of potash may be responsible for the inhibitive nature of this black pigment.

=Panel No. 24--Ochre.= While the film seems intact, it has a very mottled appearance and examination shows eruptions of rust through the film, in several places.

=Panel No. 27--Natural Barytes.= Within a year the film became pin-holed, and corrosion was apparent. At the end of three years very little of the pigment was left upon the plate, having chalked and scaled off. Barytes has proved its usefulness as a const.i.tuent of a combination type of paint, but it should not be used alone.

=Panel No. 28--Blanc Fixe.= In the same condition as Panel No. 27, but slightly more chalking and disintegration was shown.

[Ill.u.s.tration: Panel Painted with Blanc Fixe. Right Side Stripped of Paint to Show Corrosion]

[Ill.u.s.tration: Scaled Whiting Films

Chemically Active Pigments and Their Effect After Eighteen Months'

Wear]

[Ill.u.s.tration: Plate Showing Effect of Chemically Active Pigments on Oil after One Year's Wear]

=Panel No. 29--Whiting.= Plates coated with calcium carbonate or whiting in oil presented a very fair appearance at the start of the test, but they soon began to chalk and disintegrate. It is well known that whiting, being alkaline, has the property of acting on oil and causing its early disintegration by saponification. As a matter of fact, six months after the whiting plates were exposed, crumbling of the surface appeared, and twelve months was sufficient for the total destruction of the paint. At this time the rusted surface of the plates which had been painted with calcium carbonate, seemed not to rust as fast as those plates which were exposed without paint coatings, and the rust which had formed appeared to be of an even, fine texture. On the lower left-hand corner of these plates had been lettered the figures "29" and "30,"

using lampblack in oil. One of the most remarkable things which appears on the fence to-day is the perfect condition of these lampblack letters over their priming coat of calcium carbonate, standing out in clear relief against the rusted metal. This test would suggest, therefore, that if the surface of metal is properly protected with a pigment which is slightly alkaline or inhibitive in nature, and then topped with a good weather-resisting material, such as lampblack, graphite or carbon black, good results would be obtained. Further tests will be made to determine the value of this suggestion.

=Panel No. 30--Precipitated Calcium Carbonate.= Showed more rapid destruction than Panel No. 29.