Zinc-rich Paints Research Articles

ジンクリッチプライマー鋼板のプレス成形性に与える塗膜因子の影響

A zinc-rich primer painted steel sheet for automobile body has much zinc powder in paint film for the purpose of doing spot welding. A paint film which has a large quantity of pigment is brittle and susceptible to flaking by press forming, and its corrosion resistance becomes poor. Some paint film factors influencing its flaking by press forming were studied. (1) By the addition of lubricant (ex. MoS2) to paint film, the flaking of the paint film is reduced. The effect of the lubricant addition is due to the reduction of the friction coefficient of paint film. As an other effect the lubricant is coated on the die, and good lubrication appears.(2) Generally, zinc powder content of zinc-rich primer paint film is about 90 wt%. By decreasing zinc powder content of paint film, the flaking of paint film is reduced. As the paint film becomes thicker, the shear stress on it decreases and flaking of the paint film is reduced.(3) The flaking of paint film on electroplated Ni-Zn alloy steel sheet is less than that on cold rolled one.

Bolted Shear Connections with Painted Surfaces

In high-strength bolted shear connections, the load transfer between plate components is initially provided by the frictional forces developed by bolt clamping forces and friction characteristics of contact surfaces. A connection which relies on this slip resistance to transfer load is called a friction connection. When the slip resistance is exceeded, the connection slips into bearing to develop the bearing strength (bearing connection). Prior to 1974, paints on the contact surfaces were prohibited in friction connections because some early tests showed they affected adversely the slip load. The fabricator had to mask off the connection area, thus increasing the cost when friction joints and painted steel were specified. In exposed environments, the unpainted contact surfaces resulted in crevice corrosion and a subsequent deterioration of the structural painting system. Design criteria for bolted joints are given in the Specification for Structural Joints Using ASTM A325 or A490 Bolts prepared by the Research Council on Structural Connections (RCSC). The RCSC Specification gives allowable friction forces for nine different contact surface conditions based on a probability of slip concept developed by Fisher and Struik. Three types of paint were recognized for friction surface: organic and inorganic zinc-rich paint and vinyl wash. Many coatings and painting systems, especially vinyl and epoxies, which show significant improvement in corrosion protection, have been developed. Since such coatings are not reflected in the RCSC Specification, their status for use on friction surfaces is unknown.

Influence of phosphate pretreatment on durability of zinc‐rich paints

Corrosion protection efficiency of any protective system depends not only on the nature and quality of the coating system used but also on the condition of the mrface on which it is to be applied. Various metal cleaning methods include (a) chemical cleaning — solvent degreasing, alkali cleaning and acid pickling (b) mechanical cleaning — shot blasting and (c) chemical conversion coatings — phosphating. Several of the recent advances in the field of prepaint treatment of steel have had as an objective the provision of an intrinsically fine, compact, well adhered zinc phosphate coating. Studies in this direction have been carried out in Central Building Research Institute, Roorkee and conditions for a suitable phosphating process have been optimised. Some work on the development of zinc rich paints based on both inorganic as well as organic binders have already been reported. The study has been extended by evaluating the performance of these zinc rich coatings on phosphated steel panels. In this report the performance of the above mentioned coatings when applied on the phosphated steel panels have been discussed. The studies reported include the preparation of the phosphated mild steel panels having three levels of coating wight ranging between 1.5–7.5 g/m2 (obtained by varying only the immersion time and keeping other parameters similar). A cost of zinc rich paint (75m?) based on either sodium silicate or chlorinated rubber binder was then applied on these panels along with the unphosphated ones. Comparison of the corrosion protection efficiency of the various systems thus obtained was carried out by using both laboratory and accelerated laboratory tests as well as by outdoor exposure studies. The performance of the coatings on phosphated panels has been remarkedly satisfactory as compared to the unphosphated panels. This is particularly so when the coating weight of the phosphate layer is between 4.5–7.5 g/m2; there is not any marked difference in the performance of paints applied on a phosphated layer with a coating weight of about 1.5 g/m2 as compared to the unphosphated panels.

Welding cracks of Zn-contaminated stainless steel pipe

Stainless steel pipings in a chemical plant suffered from welding cracks due to contamination by zinc-rich paint. In order to establish general measures for preventing the zinc embrittlement in the above case, welding tests of stainless steel contamined by zinc-rich paint were carried out at a laboratory. A quantitative relationship between degree of zinc contamination and depth of welding crack was obtained. Several methods for the decontamination of zinc-rich paint, the detection of zinc contamination and the method for repairing cracks are indicated.

エポキシ樹脂塗装系の耐塩水性に及ぼすジンクリッチペイントの効果

エポキシ樹脂塗装系の耐塩水性に及ぼすジンクリッチペイントの効果

Aspects of galvanic action of zinc rich paints

AbstractThe cathodic protection effect of zinc in zinc pigmented coatings can be clearly recognized above a certain pigment concentration. According to the results obtained during potentiostatic polarization experiments such an effect can be expected above 90% Zn. This effect will still be present after 30 days in sodium chloride solution, provided the original concentration is 93%, while the protective effect is lossed after this time in the case of 91% Zn. The potentiostatic methods are clearly superiour to a resistance method used preferentially and can be recommended for formulation of coating materials and for testing such coating materials and coatings.

Rheological aspects of the hardening of water-borne alkali silicate zinc-rich paints

The kinetics of the reaction between zinc dust and alkali silicate in water-borne silicate zinc-rich paints was investigated on the basis of rheological measurements. The paints studied were formulated with the same zinc dust/silicate vehicle ratio. Different zinc dusts were employed. The vehicle was a litiumsodium silicate solution. Formulation included a rheological agent to prevent rapid settling of suspended zinc dust.

カレントインターラプター法によるジンクリッチペイントの防食性の評価

カレントインターラプター法によるジンクリッチペイントの防食性の評価

ジンクリッチ系プライマー塗装鋼板の自動車への利用

ジンクリッチ系プライマー塗装鋼板の自動車への利用

The protection of mild steel by zinc-rich paint in flowing aerated 0.5 M NaCl solution—III. The effect of zinc content

The effect of the rate of flow of 0.5 M NaCl solution on the corrosion rate of mild steel and steel painted with zinc-rich paints containing from 50 to 93 wt% zinc dust was investigated. The results showed that the zinc dust content necessary to ensure protection of mild steel over the full flow range up to a Reynolds number of 16,000 was 80 wt% in the dried film.

The protection of mild steel by zinc-rich paint in flowing aerated 0.5 M NaCl solution—IV. The effect of zinc oxide addition

By employing mixtures of zinc and zinc oxide it was shown that when painted surface areas are exposed to flowing aerated NaCl solutions, the total solids content is more important than the actual amount of zinc. If the total solids content in the dried film was 93%, the zinc content could be replaced by up to 43% of zinc oxide without unduly affecting the protection afforded over 144 h.

The protection of mild steel by zinc-rich paint in flowing aerated 0.5 M NaCl solution—II. The effect of exposed area ratio

Experiments were performed in aerated 0.5 M NaCl solution over a range of selected Re numbers, using electrode couples of painted steel to bare steel at varying surface ratios. Results showed that, provided the painted to bare steel ratio was high flow, effects were not harmful. The bare steel was protected by a thin grey film of protective zinc hydroxide. Areas containing iron corrosion products were afforded temporary protection by a non-protective type of bulky white corrosion product, providing the steel was being subjected to cathodic protection. Once this was lost rusting of the underlying steel restarted at these points with iron corrosion products breaking through this overlying non-protective film.

The protection of mild steel by zinc-rich paint in flowing aerated 0.5 M NaCl solutions.—I. The effect of zinc particle size

An accelerated testing procedure was used to determine the effect of average zinc dust particle size on the electrochemical behaviour of a zinc-rich chlorinated rubber primer applied to mild steel. Tests with a painted surface to exposed area ratio of 11.6 to one in flowing aerated 0.5M NaCl solution showed that a particle size of 2.5 μm provided the best protection over the flow range investigated.

Applications of electrochemistry in corrosion science and in practice

In an introduction, a statement is made on the influence of electrochemistry during the last 30 or 40 y on corrosion research and technology, with reference to opinions expressed by U. R. Evans, R. Piontelli and C. Edeleanu. A section on Fundamentals and Electrochemical Testing Methods describes the action of CITCE in developing electrochemical thermodynamics and kinetics, and their applications. It mentions the pioneer work of C. Wagner and W. Traud and the statement of F. L. LaQue on the links connecting electrochemical research and corrosion research. The author recalls the statement of M. G. Fontana on the relative practical usefulness of corrosion education and corrosion research. The practical usefulness of three series of electrochemical methods is emphasized: the polarization resistance methods, the anodic and cathodic polarization methods, and the zero-current electrode potential measurements. A third section reviews some of the most important applications of electrochemistry in anticorrosion practice. The following topics are examined: Cathodic protection Historical Hydrogen embrittlement of pipe-lines; bi-adhesive wrapping material Cathodic protection by perfect passivation: general. Protection of carbon steels in solutions containing chloride. Protection of cast iron drying cylinders in the paper industry. Protection of stainless steels in chloride containing environments. Protection of copper in the presence of waters. Protection of aluminium in sea-water Sacrificial anodes Corrodible anodes for impressed currents Non-corrodible anodes for impressed currents Anodic protection Inhibitors: general. Water treatment. Engine coolants for automobiles. Passivation of galvanized iron. Vapour-phase inhibitors Protection of metals Iron and carbon steels: electrolysis of water. Boilers. Reinforcing bars and steel pipes embedded in concrete Weathering steels Titanium Developments of alloys: general. Titanium-palladium alloys. Copper-nickel alloys. Alloys for surgical implants Chemical surface treatments: prepassivation of brasses for heat-exchangers. Thermochemical protection of stainless steels and of refractory alloys Protective coatings: general. Wash-primers and other phosphate coatings on steel. Zinc-rich paints. Benzotriazole coatings. Rust-transformers. Electroplating. Anodized aluminium Design and miscellaneous High-temperature corrosion: fused salts. Solid electrolytes. In his conclusions, the author pays tribute to those to whom we are indebted for what is now corrosion science, and to those who have put this science into practice. He expresses opinions on the future of corrosion research. However, he agrees with M. G. Fontana in believing that what is presently most needed in the struggle against corrosion is not so much research as teaching, education and common sense.

Extenders and zinc rich paints

Whilst accepting the economic necessity for adding extenders to zinc rich paints, there are several problems which need careful consideration.

Fume extraction when welding zinc-coated steels.

Methods of fume extraction have been developed for use when welding steels coated by hot dip galvanizing, by zinc metalizing, or with zinc-rich paints. For gas-shielded metal arc (e.g., MIG-CO2 welding) processes a fume extractor has been developed which surrounds the welding gun so that fumes are removed close to their point of origin. The zinc oxide fumes, which are completely removed, can be exhausted to the outside atmosphere, or they can be collected.

The Preparation of the Lyophilic Zinc Powder and its Physicochemical Properties

Lyophilic zinc powder has been prepared by subjecting zinc powder to reaction with n-butanol under high temperature and high pressure. By the microanalysis of the surface-treated zinc powder, by observation through electron microscope, and by dissolution of the zinc-rich paint film into dil. HCl, adsorption of argon at 77°K, and also by the fact that, though the surface-treated samples cannot be suspended into water, they can into organic solvent, it is found that only the surface properties of the powder are made lyophilic, causing no change to any fundamental properties of the powder, e. g. the surface area, pore structure or any chemical properties. This surface-treatment of zinc powder is understood as esterification of the acidic group of the surface oxide of zinc powder with n-butanol. The zinc-rich paint of the surface-treated zinc powder is found better dispersed in the vehicle than that of untreated native zinc powder. On the contrary, the dry film of the paint prepared from the surface-treated zinc powder proves more easily breakable than that prepared from the untreated native kind.

FOCUS ON ZINC‐2

There are many ways of protecting ferrous metals with zinc, and coating them with paint incorporating metallic zinc powder as a pigment is the most versatile. Although hot dip galvanizing remains the standard by which other forms of protection are judged, zinc paints have some very great advantages:— they are easy to apply, which may be in factory or on site; the thickness of coating can be controlled to that required for a given duration of protection; there is no limit on the size or weight of the object which can be protected (both the world's biggest ship and largest building are protected with zinc rich paints). They are preferable to galvanizing where welding or flame cutting operations are carried out subsequently, and can be made to withstand temperatures up to dull red heat.

Paints for the Protection of Steel—a Review of Research into their Modes of Action

Abstract Research over a period of about 20 years into the mechanism of the protection of steel by paint films is reviewed. possibilities are: cathodic protection achieved with zinc-rich paints; anodic passivation, by degradation products of metal soaps, notably those of lead, formed by pigment/media interaction; and resistance inhibition which depends on the structure of the paint film. Further progress may come from metal pigments such as alummIUm or magnesium with the oxide cover of the particles made conducting by alloying or surface treatment, exploration of a larger range of metal soaps, and improvement of homogeneity in crosslinking in paint films to develop maximum resistance.

The Role of Zinc in the Corrosion Protection of Offshore Structures

As a protective coating, zinc can be applied by hot dipping or by continuous, low-cost galvanizing of sheet and strip. Additional protection can be readily achieved by painting. On-site application can be achieved by zinc spraying, or by using zinc rich paint. Zinc-containing paint has proved particularly effective for offshore structures exposed to atmospheric corrosion. Coatings with inorganic vehicles give outstanding abrasion resistance, and such coatings, having over 80% zinc in the dry film, are giving good protection after twenty years. Those based on organic vehicles should have over 90% zinc in the dry film for maximum protection. They require somewhat less meticulous surface preparation, and provide a more flexible coating, but they have lower abrasion resistance.